~dkuhlman/python-training-materials/Materials

<h1>15.1. <a class="reference internal" href="#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal">os</code></a> — Miscellaneous operating system interfaces<a class="headerlink" href="#module-os" title="Permalink to this headline">¶</a></h1>

This module provides a portable way of using operating system dependent

functionality. If you just want to read or write a file see <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal">open()</code></a>, if

you want to manipulate paths, see the <a class="reference internal" href="os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal">os.path</code></a> module, and if you want to

read all the lines in all the files on the command line see the <a class="reference internal" href="fileinput.html#module-fileinput" title="fileinput: Loop over standard input or a list of files."><code class="xref py py-mod docutils literal">fileinput</code></a>

module. For creating temporary files and directories see the <a class="reference internal" href="tempfile.html#module-tempfile" title="tempfile: Generate temporary files and directories."><code class="xref py py-mod docutils literal">tempfile</code></a>

module, and for high-level file and directory handling see the <a class="reference internal" href="shutil.html#module-shutil" title="shutil: High-level file operations, including copying."><code class="xref py py-mod docutils literal">shutil</code></a>

module.

Notes on the availability of these functions:

<li>The design of all built-in operating system dependent modules of Python is

such that as long as the same functionality is available, it uses the same

interface; for example, the function <code class="docutils literal">os.stat(path)</code> returns stat

information about path in the same format (which happens to have originated

with the POSIX interface).</li>

<li>Extensions peculiar to a particular operating system are also available

through the <a class="reference internal" href="#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal">os</code></a> module, but using them is of course a threat to

portability.</li>

<li>An “Availability: Unix” note means that this function is commonly found on

Unix systems. It does not make any claims about its existence on a specific

operating system.</li>

<li>If not separately noted, all functions that claim “Availability: Unix” are

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supported on Mac OS X, which builds on a Unix core.</li>

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</ul>

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Note

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All functions in this module raise <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> in the case of invalid or

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inaccessible file names and paths, or other arguments that have the correct

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type, but are not accepted by the operating system.

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</div>

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exception <code class="descclassname">os.</code><code class="descname">error</code><a class="headerlink" href="#os.error" title="Permalink to this definition">¶</a></dt>

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<dd>An alias for the built-in <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> exception.

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</dd></dl>

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<dd>The name of the operating system dependent module imported. The following

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names have currently been registered: <code class="docutils literal">'posix'</code>, <code class="docutils literal">'nt'</code>,

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<code class="docutils literal">'os2'</code>, <code class="docutils literal">'ce'</code>, <code class="docutils literal">'java'</code>, <code class="docutils literal">'riscos'</code>.

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See also

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<a class="reference internal" href="sys.html#sys.platform" title="sys.platform"><code class="xref py py-attr docutils literal">sys.platform</code></a> has a finer granularity. <a class="reference internal" href="#os.uname" title="os.uname"><code class="xref py py-func docutils literal">os.uname()</code></a> gives

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system-dependent version information.

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The <a class="reference internal" href="platform.html#module-platform" title="platform: Retrieves as much platform identifying data as possible."><code class="xref py py-mod docutils literal">platform</code></a> module provides detailed checks for the

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system’s identity.

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</div>

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</dd></dl>

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<h2>15.1.1. Process Parameters<a class="headerlink" href="#process-parameters" title="Permalink to this headline">¶</a></h2>

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These functions and data items provide information and operate on the current

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process and user.

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<code class="descclassname">os.</code><code class="descname">environ</code><a class="headerlink" href="#os.environ" title="Permalink to this definition">¶</a></dt>

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<dd>A <a class="reference internal" href="../glossary.html#term-mapping">mapping</a> object representing the string environment. For example,

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<code class="docutils literal">environ['HOME']</code> is the pathname of your home directory (on some platforms),

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and is equivalent to <code class="docutils literal">getenv("HOME")</code> in C.

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This mapping is captured the first time the <a class="reference internal" href="#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal">os</code></a> module is imported,

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typically during Python startup as part of processing <code class="file docutils literal">site.py</code>. Changes

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to the environment made after this time are not reflected in <code class="docutils literal">os.environ</code>,

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except for changes made by modifying <code class="docutils literal">os.environ</code> directly.

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If the platform supports the <a class="reference internal" href="#os.putenv" title="os.putenv"><code class="xref py py-func docutils literal">putenv()</code></a> function, this mapping may be used

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to modify the environment as well as query the environment. <a class="reference internal" href="#os.putenv" title="os.putenv"><code class="xref py py-func docutils literal">putenv()</code></a> will

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be called automatically when the mapping is modified.

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Note

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Calling <a class="reference internal" href="#os.putenv" title="os.putenv"><code class="xref py py-func docutils literal">putenv()</code></a> directly does not change <code class="docutils literal">os.environ</code>, so it’s better

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to modify <code class="docutils literal">os.environ</code>.

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</div>

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Note

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On some platforms, including FreeBSD and Mac OS X, setting <code class="docutils literal">environ</code> may

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cause memory leaks. Refer to the system documentation for

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<code class="xref c c-func docutils literal">putenv()</code>.

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</div>

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If <a class="reference internal" href="#os.putenv" title="os.putenv"><code class="xref py py-func docutils literal">putenv()</code></a> is not provided, a modified copy of this mapping may be

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passed to the appropriate process-creation functions to cause child processes

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to use a modified environment.

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If the platform supports the <a class="reference internal" href="#os.unsetenv" title="os.unsetenv"><code class="xref py py-func docutils literal">unsetenv()</code></a> function, you can delete items in

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this mapping to unset environment variables. <a class="reference internal" href="#os.unsetenv" title="os.unsetenv"><code class="xref py py-func docutils literal">unsetenv()</code></a> will be called

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automatically when an item is deleted from <code class="docutils literal">os.environ</code>, and when

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one of the <code class="xref py py-meth docutils literal">pop()</code> or <code class="xref py py-meth docutils literal">clear()</code> methods is called.

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Changed in version 2.6: Also unset environment variables when calling <code class="xref py py-meth docutils literal">os.environ.clear()</code>

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and <code class="xref py py-meth docutils literal">os.environ.pop()</code>.

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</div>

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</dd></dl>

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<dt>

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<code class="descclassname">os.</code><code class="descname">chdir</code>(path)</dt>

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<dt>

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<code class="descclassname">os.</code><code class="descname">fchdir</code>(fd)</dt>

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<dt>

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<code class="descclassname">os.</code><code class="descname">getcwd</code>()</dt>

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<dd>These functions are described in <a class="reference internal" href="#os-file-dir">Files and Directories</a>.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">ctermid</code>()<a class="headerlink" href="#os.ctermid" title="Permalink to this definition">¶</a></dt>

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<dd>Return the filename corresponding to the controlling terminal of the process.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getegid</code>()<a class="headerlink" href="#os.getegid" title="Permalink to this definition">¶</a></dt>

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<dd>Return the effective group id of the current process. This corresponds to the

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“set id” bit on the file being executed in the current process.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">geteuid</code>()<a class="headerlink" href="#os.geteuid" title="Permalink to this definition">¶</a></dt>

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<dd>Return the current process’s effective user id.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getgid</code>()<a class="headerlink" href="#os.getgid" title="Permalink to this definition">¶</a></dt>

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<dd>Return the real group id of the current process.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getgroups</code>()<a class="headerlink" href="#os.getgroups" title="Permalink to this definition">¶</a></dt>

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<dd>Return list of supplemental group ids associated with the current process.

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Availability: Unix.

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Note

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On Mac OS X, <a class="reference internal" href="#os.getgroups" title="os.getgroups"><code class="xref py py-func docutils literal">getgroups()</code></a> behavior differs somewhat from

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other Unix platforms. If the Python interpreter was built with a

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deployment target of <code class="xref py py-const docutils literal">10.5</code> or earlier, <a class="reference internal" href="#os.getgroups" title="os.getgroups"><code class="xref py py-func docutils literal">getgroups()</code></a> returns

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the list of effective group ids associated with the current user process;

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this list is limited to a system-defined number of entries, typically 16,

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and may be modified by calls to <a class="reference internal" href="#os.setgroups" title="os.setgroups"><code class="xref py py-func docutils literal">setgroups()</code></a> if suitably privileged.

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If built with a deployment target greater than <code class="xref py py-const docutils literal">10.5</code>,

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<a class="reference internal" href="#os.getgroups" title="os.getgroups"><code class="xref py py-func docutils literal">getgroups()</code></a> returns the current group access list for the user

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associated with the effective user id of the process; the group access

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list may change over the lifetime of the process, it is not affected by

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calls to <a class="reference internal" href="#os.setgroups" title="os.setgroups"><code class="xref py py-func docutils literal">setgroups()</code></a>, and its length is not limited to 16. The

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deployment target value, <code class="xref py py-const docutils literal">MACOSX_DEPLOYMENT_TARGET</code>, can be

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obtained with <a class="reference internal" href="sysconfig.html#sysconfig.get_config_var" title="sysconfig.get_config_var"><code class="xref py py-func docutils literal">sysconfig.get_config_var()</code></a>.

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</div>

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">initgroups</code>(username, gid)<a class="headerlink" href="#os.initgroups" title="Permalink to this definition">¶</a></dt>

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<dd>Call the system initgroups() to initialize the group access list with all of

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the groups of which the specified username is a member, plus the specified

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group id.

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Availability: Unix.

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New in version 2.7.

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</div>

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getlogin</code>()<a class="headerlink" href="#os.getlogin" title="Permalink to this definition">¶</a></dt>

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<dd>Return the name of the user logged in on the controlling terminal of the

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process. For most purposes, it is more useful to use the environment

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variable <code class="xref std std-envvar docutils literal">LOGNAME</code> to find out who the user is, or

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<code class="docutils literal">pwd.getpwuid(os.getuid())[0]</code> to get the login name of the process’s real

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user id.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getpgid</code>(pid)<a class="headerlink" href="#os.getpgid" title="Permalink to this definition">¶</a></dt>

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<dd>Return the process group id of the process with process id pid. If pid is 0,

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the process group id of the current process is returned.

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Availability: Unix.

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New in version 2.3.

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</div>

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getpgrp</code>()<a class="headerlink" href="#os.getpgrp" title="Permalink to this definition">¶</a></dt>

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<dd>Return the id of the current process group.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getpid</code>()<a class="headerlink" href="#os.getpid" title="Permalink to this definition">¶</a></dt>

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<dd>Return the current process id.

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Availability: Unix, Windows.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getppid</code>()<a class="headerlink" href="#os.getppid" title="Permalink to this definition">¶</a></dt>

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<dd>Return the parent’s process id.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getresuid</code>()<a class="headerlink" href="#os.getresuid" title="Permalink to this definition">¶</a></dt>

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<dd>Return a tuple (ruid, euid, suid) denoting the current process’s

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real, effective, and saved user ids.

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Availability: Unix.

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New in version 2.7.

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</div>

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getresgid</code>()<a class="headerlink" href="#os.getresgid" title="Permalink to this definition">¶</a></dt>

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<dd>Return a tuple (rgid, egid, sgid) denoting the current process’s

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real, effective, and saved group ids.

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Availability: Unix.

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New in version 2.7.

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</div>

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getuid</code>()<a class="headerlink" href="#os.getuid" title="Permalink to this definition">¶</a></dt>

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<dd>Return the current process’s real user id.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getenv</code>(varname[, value])<a class="headerlink" href="#os.getenv" title="Permalink to this definition">¶</a></dt>

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<dd>Return the value of the environment variable varname if it exists, or value

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if it doesn’t. value defaults to <code class="docutils literal">None</code>.

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Availability: most flavors of Unix, Windows.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">putenv</code>(varname, value)<a class="headerlink" href="#os.putenv" title="Permalink to this definition">¶</a></dt>

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<dd>Set the environment variable named varname to the string value. Such

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changes to the environment affect subprocesses started with <a class="reference internal" href="#os.system" title="os.system"><code class="xref py py-func docutils literal">os.system()</code></a>,

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<a class="reference internal" href="#os.popen" title="os.popen"><code class="xref py py-func docutils literal">popen()</code></a> or <a class="reference internal" href="#os.fork" title="os.fork"><code class="xref py py-func docutils literal">fork()</code></a> and <a class="reference internal" href="#os.execv" title="os.execv"><code class="xref py py-func docutils literal">execv()</code></a>.

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Availability: most flavors of Unix, Windows.

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Note

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On some platforms, including FreeBSD and Mac OS X, setting <code class="docutils literal">environ</code> may

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cause memory leaks. Refer to the system documentation for putenv.

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</div>

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When <a class="reference internal" href="#os.putenv" title="os.putenv"><code class="xref py py-func docutils literal">putenv()</code></a> is supported, assignments to items in <code class="docutils literal">os.environ</code> are

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automatically translated into corresponding calls to <a class="reference internal" href="#os.putenv" title="os.putenv"><code class="xref py py-func docutils literal">putenv()</code></a>; however,

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calls to <a class="reference internal" href="#os.putenv" title="os.putenv"><code class="xref py py-func docutils literal">putenv()</code></a> don’t update <code class="docutils literal">os.environ</code>, so it is actually

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preferable to assign to items of <code class="docutils literal">os.environ</code>.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setegid</code>(egid)<a class="headerlink" href="#os.setegid" title="Permalink to this definition">¶</a></dt>

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<dd>Set the current process’s effective group id.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">seteuid</code>(euid)<a class="headerlink" href="#os.seteuid" title="Permalink to this definition">¶</a></dt>

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<dd>Set the current process’s effective user id.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setgid</code>(gid)<a class="headerlink" href="#os.setgid" title="Permalink to this definition">¶</a></dt>

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<dd>Set the current process’ group id.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setgroups</code>(groups)<a class="headerlink" href="#os.setgroups" title="Permalink to this definition">¶</a></dt>

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<dd>Set the list of supplemental group ids associated with the current process to

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groups. groups must be a sequence, and each element must be an integer

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identifying a group. This operation is typically available only to the superuser.

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Availability: Unix.

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New in version 2.2.

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</div>

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Note

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On Mac OS X, the length of groups may not exceed the

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system-defined maximum number of effective group ids, typically 16.

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See the documentation for <a class="reference internal" href="#os.getgroups" title="os.getgroups"><code class="xref py py-func docutils literal">getgroups()</code></a> for cases where it may not

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return the same group list set by calling setgroups().

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</div>

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setpgrp</code>()<a class="headerlink" href="#os.setpgrp" title="Permalink to this definition">¶</a></dt>

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<dd>Call the system call <code class="xref c c-func docutils literal">setpgrp()</code> or <code class="xref c c-func docutils literal">setpgrp(0, 0)()</code> depending on

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which version is implemented (if any). See the Unix manual for the semantics.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setpgid</code>(pid, pgrp)<a class="headerlink" href="#os.setpgid" title="Permalink to this definition">¶</a></dt>

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<dd>Call the system call <code class="xref c c-func docutils literal">setpgid()</code> to set the process group id of the

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process with id pid to the process group with id pgrp. See the Unix manual

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for the semantics.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setregid</code>(rgid, egid)<a class="headerlink" href="#os.setregid" title="Permalink to this definition">¶</a></dt>

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<dd>Set the current process’s real and effective group ids.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setresgid</code>(rgid, egid, sgid)<a class="headerlink" href="#os.setresgid" title="Permalink to this definition">¶</a></dt>

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<dd>Set the current process’s real, effective, and saved group ids.

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Availability: Unix.

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New in version 2.7.

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</div>

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setresuid</code>(ruid, euid, suid)<a class="headerlink" href="#os.setresuid" title="Permalink to this definition">¶</a></dt>

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<dd>Set the current process’s real, effective, and saved user ids.

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Availability: Unix.

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New in version 2.7.

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</div>

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setreuid</code>(ruid, euid)<a class="headerlink" href="#os.setreuid" title="Permalink to this definition">¶</a></dt>

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<dd>Set the current process’s real and effective user ids.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">getsid</code>(pid)<a class="headerlink" href="#os.getsid" title="Permalink to this definition">¶</a></dt>

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<dd>Call the system call <code class="xref c c-func docutils literal">getsid()</code>. See the Unix manual for the semantics.

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Availability: Unix.

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New in version 2.4.

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</div>

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setsid</code>()<a class="headerlink" href="#os.setsid" title="Permalink to this definition">¶</a></dt>

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<dd>Call the system call <code class="xref c c-func docutils literal">setsid()</code>. See the Unix manual for the semantics.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">setuid</code>(uid)<a class="headerlink" href="#os.setuid" title="Permalink to this definition">¶</a></dt>

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<dd>Set the current process’s user id.

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Availability: Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">strerror</code>(code)<a class="headerlink" href="#os.strerror" title="Permalink to this definition">¶</a></dt>

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<dd>Return the error message corresponding to the error code in code.

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On platforms where <code class="xref c c-func docutils literal">strerror()</code> returns <code class="docutils literal">NULL</code> when given an unknown

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error number, <a class="reference internal" href="exceptions.html#exceptions.ValueError" title="exceptions.ValueError"><code class="xref py py-exc docutils literal">ValueError</code></a> is raised.

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Availability: Unix, Windows.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">umask</code>(mask)<a class="headerlink" href="#os.umask" title="Permalink to this definition">¶</a></dt>

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<dd>Set the current numeric umask and return the previous umask.

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Availability: Unix, Windows.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">uname</code>()<a class="headerlink" href="#os.uname" title="Permalink to this definition">¶</a></dt>

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<dd>Return a 5-tuple containing information identifying the current operating

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system. The tuple contains 5 strings: <code class="docutils literal">(sysname, nodename, release, version,

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machine)</code>. Some systems truncate the nodename to 8 characters or to the

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leading component; a better way to get the hostname is

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<a class="reference internal" href="socket.html#socket.gethostname" title="socket.gethostname"><code class="xref py py-func docutils literal">socket.gethostname()</code></a> or even

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<code class="docutils literal">socket.gethostbyaddr(socket.gethostname())</code>.

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Availability: recent flavors of Unix.

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</dd></dl>

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<code class="descclassname">os.</code><code class="descname">unsetenv</code>(varname)<a class="headerlink" href="#os.unsetenv" title="Permalink to this definition">¶</a></dt>

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<dd>Unset (delete) the environment variable named varname. Such changes to the

489

environment affect subprocesses started with <a class="reference internal" href="#os.system" title="os.system"><code class="xref py py-func docutils literal">os.system()</code></a>, <a class="reference internal" href="#os.popen" title="os.popen"><code class="xref py py-func docutils literal">popen()</code></a> or

490

<a class="reference internal" href="#os.fork" title="os.fork"><code class="xref py py-func docutils literal">fork()</code></a> and <a class="reference internal" href="#os.execv" title="os.execv"><code class="xref py py-func docutils literal">execv()</code></a>.

491

When <a class="reference internal" href="#os.unsetenv" title="os.unsetenv"><code class="xref py py-func docutils literal">unsetenv()</code></a> is supported, deletion of items in <code class="docutils literal">os.environ</code> is

492

automatically translated into a corresponding call to <a class="reference internal" href="#os.unsetenv" title="os.unsetenv"><code class="xref py py-func docutils literal">unsetenv()</code></a>; however,

493

calls to <a class="reference internal" href="#os.unsetenv" title="os.unsetenv"><code class="xref py py-func docutils literal">unsetenv()</code></a> don’t update <code class="docutils literal">os.environ</code>, so it is actually

494

preferable to delete items of <code class="docutils literal">os.environ</code>.

495

Availability: most flavors of Unix, Windows.

496

</dd></dl>

497

498

</div>

499

500

<h2>15.1.2. File Object Creation<a class="headerlink" href="#file-object-creation" title="Permalink to this headline">¶</a></h2>

501

These functions create new file objects. (See also <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal">open()</code></a>.)

502

503

504

<code class="descclassname">os.</code><code class="descname">fdopen</code>(fd[, mode[, bufsize]])<a class="headerlink" href="#os.fdopen" title="Permalink to this definition">¶</a></dt>

505

<dd>Return an open file object connected to the file descriptor fd. The mode

506

and bufsize arguments have the same meaning as the corresponding arguments

507

to the built-in <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal">open()</code></a> function. If <a class="reference internal" href="#os.fdopen" title="os.fdopen"><code class="xref py py-func docutils literal">fdopen()</code></a> raises an

508

exception, it leaves fd untouched (unclosed).

509

Availability: Unix, Windows.

510

511

Changed in version 2.3: When specified, the mode argument must now start with one of the letters

512

<code class="docutils literal">'r'</code>, <code class="docutils literal">'w'</code>, or <code class="docutils literal">'a'</code>, otherwise a <a class="reference internal" href="exceptions.html#exceptions.ValueError" title="exceptions.ValueError"><code class="xref py py-exc docutils literal">ValueError</code></a> is raised.

513

</div>

514

515

Changed in version 2.5: On Unix, when the mode argument starts with <code class="docutils literal">'a'</code>, the O_APPEND flag is

516

set on the file descriptor (which the <code class="xref c c-func docutils literal">fdopen()</code> implementation already

517

does on most platforms).

518

</div>

519

</dd></dl>

520

521

522

523

<code class="descclassname">os.</code><code class="descname">popen</code>(command[, mode[, bufsize]])<a class="headerlink" href="#os.popen" title="Permalink to this definition">¶</a></dt>

524

<dd>Open a pipe to or from command. The return value is an open file object

525

connected to the pipe, which can be read or written depending on whether mode

526

is <code class="docutils literal">'r'</code> (default) or <code class="docutils literal">'w'</code>. The bufsize argument has the same meaning as

527

the corresponding argument to the built-in <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal">open()</code></a> function. The exit

528

status of the command (encoded in the format specified for <a class="reference internal" href="#os.wait" title="os.wait"><code class="xref py py-func docutils literal">wait()</code></a>) is

529

available as the return value of the <a class="reference internal" href="stdtypes.html#file.close" title="file.close"><code class="xref py py-meth docutils literal">close()</code></a> method of the file object,

530

except that when the exit status is zero (termination without errors), <code class="docutils literal">None</code>

531

is returned.

532

Availability: Unix, Windows.

533

534

Deprecated since version 2.6: This function is obsolete. Use the <a class="reference internal" href="subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal">subprocess</code></a> module. Check

535

especially the <a class="reference internal" href="subprocess.html#subprocess-replacements">Replacing Older Functions with the subprocess Module</a> section.

536

</div>

537

538

Changed in version 2.0: This function worked unreliably under Windows in earlier versions of Python.

539

This was due to the use of the <code class="xref c c-func docutils literal">_popen()</code> function from the libraries

540

provided with Windows. Newer versions of Python do not use the broken

541

implementation from the Windows libraries.

542

</div>

543

</dd></dl>

544

545

546

547

<code class="descclassname">os.</code><code class="descname">tmpfile</code>()<a class="headerlink" href="#os.tmpfile" title="Permalink to this definition">¶</a></dt>

548

<dd>Return a new file object opened in update mode (<code class="docutils literal">w+b</code>). The file has no

549

directory entries associated with it and will be automatically deleted once

550

there are no file descriptors for the file.

551

Availability: Unix, Windows.

552

</dd></dl>

553

554

There are a number of different <code class="xref py py-func docutils literal">popen*()</code> functions that provide slightly

555

different ways to create subprocesses.

556

557

Deprecated since version 2.6: All of the <code class="xref py py-func docutils literal">popen*()</code> functions are obsolete. Use the <a class="reference internal" href="subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal">subprocess</code></a>

558

module.

559

</div>

560

For each of the <code class="xref py py-func docutils literal">popen*()</code> variants, if bufsize is specified, it

561

specifies the buffer size for the I/O pipes. mode, if provided, should be the

562

string <code class="docutils literal">'b'</code> or <code class="docutils literal">'t'</code>; on Windows this is needed to determine whether the

563

file objects should be opened in binary or text mode. The default value for

564

mode is <code class="docutils literal">'t'</code>.

565

Also, for each of these variants, on Unix, cmd may be a sequence, in which

566

case arguments will be passed directly to the program without shell intervention

567

(as with <a class="reference internal" href="#os.spawnv" title="os.spawnv"><code class="xref py py-func docutils literal">os.spawnv()</code></a>). If cmd is a string it will be passed to the shell

568

(as with <a class="reference internal" href="#os.system" title="os.system"><code class="xref py py-func docutils literal">os.system()</code></a>).

569

These methods do not make it possible to retrieve the exit status from the child

570

processes. The only way to control the input and output streams and also

571

retrieve the return codes is to use the <a class="reference internal" href="subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal">subprocess</code></a> module; these are only

572

available on Unix.

573

For a discussion of possible deadlock conditions related to the use of these

574

functions, see <a class="reference internal" href="popen2.html#popen2-flow-control">Flow Control Issues</a>.

575

576

577

<code class="descclassname">os.</code><code class="descname">popen2</code>(cmd[, mode[, bufsize]])<a class="headerlink" href="#os.popen2" title="Permalink to this definition">¶</a></dt>

578

<dd>Execute cmd as a sub-process and return the file objects <code class="docutils literal">(child_stdin,

579

child_stdout)</code>.

580

581

582

especially the <a class="reference internal" href="subprocess.html#subprocess-replacements">Replacing Older Functions with the subprocess Module</a> section.

583

</div>

584

Availability: Unix, Windows.

585

586

New in version 2.0.

587

</div>

588

</dd></dl>

589

590

591

592

<code class="descclassname">os.</code><code class="descname">popen3</code>(cmd[, mode[, bufsize]])<a class="headerlink" href="#os.popen3" title="Permalink to this definition">¶</a></dt>

593

<dd>Execute cmd as a sub-process and return the file objects <code class="docutils literal">(child_stdin,

594

child_stdout, child_stderr)</code>.

595

596

597

especially the <a class="reference internal" href="subprocess.html#subprocess-replacements">Replacing Older Functions with the subprocess Module</a> section.

598

</div>

599

Availability: Unix, Windows.

600

601

New in version 2.0.

602

</div>

603

</dd></dl>

604

605

606

607

<code class="descclassname">os.</code><code class="descname">popen4</code>(cmd[, mode[, bufsize]])<a class="headerlink" href="#os.popen4" title="Permalink to this definition">¶</a></dt>

608

<dd>Execute cmd as a sub-process and return the file objects <code class="docutils literal">(child_stdin,

609

child_stdout_and_stderr)</code>.

610

611

612

especially the <a class="reference internal" href="subprocess.html#subprocess-replacements">Replacing Older Functions with the subprocess Module</a> section.

613

</div>

614

Availability: Unix, Windows.

615

616

New in version 2.0.

617

</div>

618

</dd></dl>

619

620

(Note that <code class="docutils literal">child_stdin, child_stdout, and child_stderr</code> are named from the

621

point of view of the child process, so child_stdin is the child’s standard

622

input.)

623

This functionality is also available in the <a class="reference internal" href="popen2.html#module-popen2" title="popen2: Subprocesses with accessible standard I/O streams. (deprecated)"><code class="xref py py-mod docutils literal">popen2</code></a> module using functions

624

of the same names, but the return values of those functions have a different

625

order.

626

</div>

627

628

<h2>15.1.3. File Descriptor Operations<a class="headerlink" href="#file-descriptor-operations" title="Permalink to this headline">¶</a></h2>

629

These functions operate on I/O streams referenced using file descriptors.

630

File descriptors are small integers corresponding to a file that has been opened

631

by the current process. For example, standard input is usually file descriptor

632

0, standard output is 1, and standard error is 2. Further files opened by a

633

process will then be assigned 3, 4, 5, and so forth. The name “file descriptor”

634

is slightly deceptive; on Unix platforms, sockets and pipes are also referenced

635

by file descriptors.

636

The <a class="reference internal" href="stdtypes.html#file.fileno" title="file.fileno"><code class="xref py py-meth docutils literal">fileno()</code></a> method can be used to obtain the file descriptor

637

associated with a file object when required. Note that using the file

638

descriptor directly will bypass the file object methods, ignoring aspects such

639

as internal buffering of data.

640

641

642

<code class="descclassname">os.</code><code class="descname">close</code>(fd)<a class="headerlink" href="#os.close" title="Permalink to this definition">¶</a></dt>

643

<dd>Close file descriptor fd.

644

Availability: Unix, Windows.

645

646

Note

647

This function is intended for low-level I/O and must be applied to a file

648

descriptor as returned by <a class="reference internal" href="#os.open" title="os.open"><code class="xref py py-func docutils literal">os.open()</code></a> or <a class="reference internal" href="#os.pipe" title="os.pipe"><code class="xref py py-func docutils literal">pipe()</code></a>. To close a “file

649

object” returned by the built-in function <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal">open()</code></a> or by <a class="reference internal" href="#os.popen" title="os.popen"><code class="xref py py-func docutils literal">popen()</code></a> or

650

<a class="reference internal" href="#os.fdopen" title="os.fdopen"><code class="xref py py-func docutils literal">fdopen()</code></a>, use its <a class="reference internal" href="io.html#io.IOBase.close" title="io.IOBase.close"><code class="xref py py-meth docutils literal">close()</code></a> method.

651

</div>

652

</dd></dl>

653

654

655

656

<code class="descclassname">os.</code><code class="descname">closerange</code>(fd_low, fd_high)<a class="headerlink" href="#os.closerange" title="Permalink to this definition">¶</a></dt>

657

<dd>Close all file descriptors from fd_low (inclusive) to fd_high (exclusive),

658

ignoring errors. Equivalent to:

659

<div class="highlight-python"><div class="highlight"><pre>for fd in xrange(fd_low, fd_high):

660

try:

661

os.close(fd)

662

except OSError:

663

pass

664

</pre></div>

665

</div>

666

Availability: Unix, Windows.

667

668

New in version 2.6.

669

</div>

670

</dd></dl>

671

672

673

674

675

<dd>Return a duplicate of file descriptor fd.

676

Availability: Unix, Windows.

677

</dd></dl>

678

679

680

681

682

<dd>Duplicate file descriptor fd to fd2, closing the latter first if necessary.

683

Availability: Unix, Windows.

684

</dd></dl>

685

686

687

688

<code class="descclassname">os.</code><code class="descname">fchmod</code>(fd, mode)<a class="headerlink" href="#os.fchmod" title="Permalink to this definition">¶</a></dt>

689

<dd>Change the mode of the file given by fd to the numeric mode. See the docs

690

for <a class="reference internal" href="#os.chmod" title="os.chmod"><code class="xref py py-func docutils literal">chmod()</code></a> for possible values of mode.

691

Availability: Unix.

692

693

New in version 2.6.

694

</div>

695

</dd></dl>

696

697

698

699

<code class="descclassname">os.</code><code class="descname">fchown</code>(fd, uid, gid)<a class="headerlink" href="#os.fchown" title="Permalink to this definition">¶</a></dt>

700

<dd>Change the owner and group id of the file given by fd to the numeric uid

701

and gid. To leave one of the ids unchanged, set it to -1.

702

Availability: Unix.

703

704

New in version 2.6.

705

</div>

706

</dd></dl>

707

708

709

710

<code class="descclassname">os.</code><code class="descname">fdatasync</code>(fd)<a class="headerlink" href="#os.fdatasync" title="Permalink to this definition">¶</a></dt>

711

<dd>Force write of file with filedescriptor fd to disk. Does not force update of

712

metadata.

713

Availability: Unix.

714

715

Note

716

This function is not available on MacOS.

717

</div>

718

</dd></dl>

719

720

721

722

<code class="descclassname">os.</code><code class="descname">fpathconf</code>(fd, name)<a class="headerlink" href="#os.fpathconf" title="Permalink to this definition">¶</a></dt>

723

<dd>Return system configuration information relevant to an open file. name

724

specifies the configuration value to retrieve; it may be a string which is the

725

name of a defined system value; these names are specified in a number of

726

standards (POSIX.1, Unix 95, Unix 98, and others). Some platforms define

727

additional names as well. The names known to the host operating system are

728

given in the <code class="docutils literal">pathconf_names</code> dictionary. For configuration variables not

729

included in that mapping, passing an integer for name is also accepted.

730

If name is a string and is not known, <a class="reference internal" href="exceptions.html#exceptions.ValueError" title="exceptions.ValueError"><code class="xref py py-exc docutils literal">ValueError</code></a> is raised. If a

731

specific value for name is not supported by the host system, even if it is

732

included in <code class="docutils literal">pathconf_names</code>, an <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> is raised with

733

<a class="reference internal" href="errno.html#errno.EINVAL" title="errno.EINVAL"><code class="xref py py-const docutils literal">errno.EINVAL</code></a> for the error number.

734

Availability: Unix.

735

</dd></dl>

736

737

738

739

<code class="descclassname">os.</code><code class="descname">fstat</code>(fd)<a class="headerlink" href="#os.fstat" title="Permalink to this definition">¶</a></dt>

740

<dd>Return status for file descriptor fd, like <a class="reference internal" href="#os.stat" title="os.stat"><code class="xref py py-func docutils literal">stat()</code></a>.

741

Availability: Unix, Windows.

742

</dd></dl>

743

744

745

746

<code class="descclassname">os.</code><code class="descname">fstatvfs</code>(fd)<a class="headerlink" href="#os.fstatvfs" title="Permalink to this definition">¶</a></dt>

747

<dd>Return information about the filesystem containing the file associated with file

748

descriptor fd, like <a class="reference internal" href="statvfs.html#module-statvfs" title="statvfs: Constants for interpreting the result of os.statvfs(). (deprecated)"><code class="xref py py-func docutils literal">statvfs()</code></a>.

749

Availability: Unix.

750

</dd></dl>

751

752

753

754

<code class="descclassname">os.</code><code class="descname">fsync</code>(fd)<a class="headerlink" href="#os.fsync" title="Permalink to this definition">¶</a></dt>

755

<dd>Force write of file with filedescriptor fd to disk. On Unix, this calls the

756

native <code class="xref c c-func docutils literal">fsync()</code> function; on Windows, the MS <code class="xref c c-func docutils literal">_commit()</code> function.

757

If you’re starting with a Python file object f, first do <code class="docutils literal">f.flush()</code>, and

758

then do <code class="docutils literal">os.fsync(f.fileno())</code>, to ensure that all internal buffers associated

759

with f are written to disk.

760

Availability: Unix, and Windows starting in 2.2.3.

761

</dd></dl>

762

763

764

765

<code class="descclassname">os.</code><code class="descname">ftruncate</code>(fd, length)<a class="headerlink" href="#os.ftruncate" title="Permalink to this definition">¶</a></dt>

766

<dd>Truncate the file corresponding to file descriptor fd, so that it is at most

767

length bytes in size.

768

Availability: Unix.

769

</dd></dl>

770

771

772

773

<code class="descclassname">os.</code><code class="descname">isatty</code>(fd)<a class="headerlink" href="#os.isatty" title="Permalink to this definition">¶</a></dt>

774

<dd>Return <code class="docutils literal">True</code> if the file descriptor fd is open and connected to a

775

tty(-like) device, else <code class="docutils literal">False</code>.

776

</dd></dl>

777

778

779

780

<code class="descclassname">os.</code><code class="descname">lseek</code>(fd, pos, how)<a class="headerlink" href="#os.lseek" title="Permalink to this definition">¶</a></dt>

781

<dd>Set the current position of file descriptor fd to position pos, modified

782

by how: <a class="reference internal" href="#os.SEEK_SET" title="os.SEEK_SET"><code class="xref py py-const docutils literal">SEEK_SET</code></a> or <code class="docutils literal">0</code> to set the position relative to the

783

beginning of the file; <a class="reference internal" href="#os.SEEK_CUR" title="os.SEEK_CUR"><code class="xref py py-const docutils literal">SEEK_CUR</code></a> or <code class="docutils literal">1</code> to set it relative to the

784

current position; <a class="reference internal" href="#os.SEEK_END" title="os.SEEK_END"><code class="xref py py-const docutils literal">SEEK_END</code></a> or <code class="docutils literal">2</code> to set it relative to the end of

785

the file. Return the new cursor position in bytes, starting from the beginning.

786

Availability: Unix, Windows.

787

</dd></dl>

788

789

790

791

792

793

794

795

796

<dd>Parameters to the <a class="reference internal" href="#os.lseek" title="os.lseek"><code class="xref py py-func docutils literal">lseek()</code></a> function. Their values are 0, 1, and 2,

797

respectively.

798

Availability: Windows, Unix.

799

800

New in version 2.5.

801

</div>

802

</dd></dl>

803

804

805

806

<code class="descclassname">os.</code><code class="descname">open</code>(file, flags[, mode])<a class="headerlink" href="#os.open" title="Permalink to this definition">¶</a></dt>

807

<dd>Open the file file and set various flags according to flags and possibly its

808

mode according to mode. The default mode is <code class="docutils literal">0777</code> (octal), and the

809

current umask value is first masked out. Return the file descriptor for the

810

newly opened file.

811

For a description of the flag and mode values, see the C run-time documentation;

812

flag constants (like <a class="reference internal" href="#os.O_RDONLY" title="os.O_RDONLY"><code class="xref py py-const docutils literal">O_RDONLY</code></a> and <a class="reference internal" href="#os.O_WRONLY" title="os.O_WRONLY"><code class="xref py py-const docutils literal">O_WRONLY</code></a>) are defined in

813

this module too (see <a class="reference internal" href="#open-constants">open() flag constants</a>). In particular, on Windows adding

814

<a class="reference internal" href="#os.O_BINARY" title="os.O_BINARY"><code class="xref py py-const docutils literal">O_BINARY</code></a> is needed to open files in binary mode.

815

Availability: Unix, Windows.

816

817

Note

818

This function is intended for low-level I/O. For normal usage, use the

819

built-in function <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal">open()</code></a>, which returns a “file object” with

820

<a class="reference internal" href="stdtypes.html#file.read" title="file.read"><code class="xref py py-meth docutils literal">read()</code></a> and <a class="reference internal" href="stdtypes.html#file.write" title="file.write"><code class="xref py py-meth docutils literal">write()</code></a> methods (and many more). To

821

wrap a file descriptor in a “file object”, use <a class="reference internal" href="#os.fdopen" title="os.fdopen"><code class="xref py py-func docutils literal">fdopen()</code></a>.

822

</div>

823

</dd></dl>

824

825

826

827

<code class="descclassname">os.</code><code class="descname">openpty</code>()<a class="headerlink" href="#os.openpty" title="Permalink to this definition">¶</a></dt>

828

<dd>Open a new pseudo-terminal pair. Return a pair of file descriptors <code class="docutils literal">(master,

829

slave)</code> for the pty and the tty, respectively. For a (slightly) more portable

830

approach, use the <a class="reference internal" href="pty.html#module-pty" title="pty: Pseudo-Terminal Handling for Linux. (Linux)"><code class="xref py py-mod docutils literal">pty</code></a> module.

831

Availability: some flavors of Unix.

832

</dd></dl>

833

834

835

836

837

<dd>Create a pipe. Return a pair of file descriptors <code class="docutils literal">(r, w)</code> usable for reading

838

and writing, respectively.

839

Availability: Unix, Windows.

840

</dd></dl>

841

842

843

844

845

<dd>Read at most n bytes from file descriptor fd. Return a string containing the

846

bytes read. If the end of the file referred to by fd has been reached, an

847

empty string is returned.

848

Availability: Unix, Windows.

849

850

Note

851

This function is intended for low-level I/O and must be applied to a file

852

853

returned by the built-in function <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal">open()</code></a> or by <a class="reference internal" href="#os.popen" title="os.popen"><code class="xref py py-func docutils literal">popen()</code></a> or

854

<a class="reference internal" href="#os.fdopen" title="os.fdopen"><code class="xref py py-func docutils literal">fdopen()</code></a>, or <a class="reference internal" href="sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal">sys.stdin</code></a>, use its <a class="reference internal" href="stdtypes.html#file.read" title="file.read"><code class="xref py py-meth docutils literal">read()</code></a> or

855

<a class="reference internal" href="stdtypes.html#file.readline" title="file.readline"><code class="xref py py-meth docutils literal">readline()</code></a> methods.

856

</div>

857

</dd></dl>

858

859

860

861

<code class="descclassname">os.</code><code class="descname">tcgetpgrp</code>(fd)<a class="headerlink" href="#os.tcgetpgrp" title="Permalink to this definition">¶</a></dt>

862

<dd>Return the process group associated with the terminal given by fd (an open

863

file descriptor as returned by <a class="reference internal" href="#os.open" title="os.open"><code class="xref py py-func docutils literal">os.open()</code></a>).

864

Availability: Unix.

865

</dd></dl>

866

867

868

869

<code class="descclassname">os.</code><code class="descname">tcsetpgrp</code>(fd, pg)<a class="headerlink" href="#os.tcsetpgrp" title="Permalink to this definition">¶</a></dt>

870

<dd>Set the process group associated with the terminal given by fd (an open file

871

872

Availability: Unix.

873

</dd></dl>

874

875

876

877

<code class="descclassname">os.</code><code class="descname">ttyname</code>(fd)<a class="headerlink" href="#os.ttyname" title="Permalink to this definition">¶</a></dt>

878

<dd>Return a string which specifies the terminal device associated with

879

file descriptor fd. If fd is not associated with a terminal device, an

880

exception is raised.

881

Availability: Unix.

882

</dd></dl>

883

884

885

886

<code class="descclassname">os.</code><code class="descname">write</code>(fd, str)<a class="headerlink" href="#os.write" title="Permalink to this definition">¶</a></dt>

887

<dd>Write the string str to file descriptor fd. Return the number of bytes

888

actually written.

889

Availability: Unix, Windows.

890

891

Note

892

This function is intended for low-level I/O and must be applied to a file

893

894

895

<a class="reference internal" href="#os.fdopen" title="os.fdopen"><code class="xref py py-func docutils literal">fdopen()</code></a>, or <a class="reference internal" href="sys.html#sys.stdout" title="sys.stdout"><code class="xref py py-data docutils literal">sys.stdout</code></a> or <a class="reference internal" href="sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal">sys.stderr</code></a>, use its

896

<a class="reference internal" href="stdtypes.html#file.write" title="file.write"><code class="xref py py-meth docutils literal">write()</code></a> method.

897

</div>

898

</dd></dl>

899

900

901

<h3>15.1.3.1. <code class="docutils literal">open()</code> flag constants<a class="headerlink" href="#open-flag-constants" title="Permalink to this headline">¶</a></h3>

902

The following constants are options for the flags parameter to the

903

<a class="reference internal" href="#os.open" title="os.open"><code class="xref py py-func docutils literal">open()</code></a> function. They can be combined using the bitwise OR operator

904

<code class="docutils literal">|</code>. Some of them are not available on all platforms. For descriptions of

905

their availability and use, consult the open(2) manual page on Unix

906

or <a class="reference external" href="http://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx">the MSDN</a> on Windows.

907

908

909

<code class="descclassname">os.</code><code class="descname">O_RDONLY</code><a class="headerlink" href="#os.O_RDONLY" title="Permalink to this definition">¶</a></dt>

910

911

<code class="descclassname">os.</code><code class="descname">O_WRONLY</code><a class="headerlink" href="#os.O_WRONLY" title="Permalink to this definition">¶</a></dt>

912

913

914

915

<code class="descclassname">os.</code><code class="descname">O_APPEND</code><a class="headerlink" href="#os.O_APPEND" title="Permalink to this definition">¶</a></dt>

916

917

<code class="descclassname">os.</code><code class="descname">O_CREAT</code><a class="headerlink" href="#os.O_CREAT" title="Permalink to this definition">¶</a></dt>

918

919

920

921

<code class="descclassname">os.</code><code class="descname">O_TRUNC</code><a class="headerlink" href="#os.O_TRUNC" title="Permalink to this definition">¶</a></dt>

922

<dd>These constants are available on Unix and Windows.

923

</dd></dl>

924

925

926

927

<code class="descclassname">os.</code><code class="descname">O_DSYNC</code><a class="headerlink" href="#os.O_DSYNC" title="Permalink to this definition">¶</a></dt>

928

929

<code class="descclassname">os.</code><code class="descname">O_RSYNC</code><a class="headerlink" href="#os.O_RSYNC" title="Permalink to this definition">¶</a></dt>

930

931

932

933

<code class="descclassname">os.</code><code class="descname">O_NDELAY</code><a class="headerlink" href="#os.O_NDELAY" title="Permalink to this definition">¶</a></dt>

934

935

<code class="descclassname">os.</code><code class="descname">O_NONBLOCK</code><a class="headerlink" href="#os.O_NONBLOCK" title="Permalink to this definition">¶</a></dt>

936

937

<code class="descclassname">os.</code><code class="descname">O_NOCTTY</code><a class="headerlink" href="#os.O_NOCTTY" title="Permalink to this definition">¶</a></dt>

938

939

<code class="descclassname">os.</code><code class="descname">O_SHLOCK</code><a class="headerlink" href="#os.O_SHLOCK" title="Permalink to this definition">¶</a></dt>

940

941

<code class="descclassname">os.</code><code class="descname">O_EXLOCK</code><a class="headerlink" href="#os.O_EXLOCK" title="Permalink to this definition">¶</a></dt>

942

<dd>These constants are only available on Unix.

943

</dd></dl>

944

945

946

947

<code class="descclassname">os.</code><code class="descname">O_BINARY</code><a class="headerlink" href="#os.O_BINARY" title="Permalink to this definition">¶</a></dt>

948

949

<code class="descclassname">os.</code><code class="descname">O_NOINHERIT</code><a class="headerlink" href="#os.O_NOINHERIT" title="Permalink to this definition">¶</a></dt>

950

951

<code class="descclassname">os.</code><code class="descname">O_SHORT_LIVED</code><a class="headerlink" href="#os.O_SHORT_LIVED" title="Permalink to this definition">¶</a></dt>

952

953

<code class="descclassname">os.</code><code class="descname">O_TEMPORARY</code><a class="headerlink" href="#os.O_TEMPORARY" title="Permalink to this definition">¶</a></dt>

954

955

<code class="descclassname">os.</code><code class="descname">O_RANDOM</code><a class="headerlink" href="#os.O_RANDOM" title="Permalink to this definition">¶</a></dt>

956

957

<code class="descclassname">os.</code><code class="descname">O_SEQUENTIAL</code><a class="headerlink" href="#os.O_SEQUENTIAL" title="Permalink to this definition">¶</a></dt>

958

959

960

<dd>These constants are only available on Windows.

961

</dd></dl>

962

963

964

965

<code class="descclassname">os.</code><code class="descname">O_ASYNC</code><a class="headerlink" href="#os.O_ASYNC" title="Permalink to this definition">¶</a></dt>

966

967

<code class="descclassname">os.</code><code class="descname">O_DIRECT</code><a class="headerlink" href="#os.O_DIRECT" title="Permalink to this definition">¶</a></dt>

968

969

<code class="descclassname">os.</code><code class="descname">O_DIRECTORY</code><a class="headerlink" href="#os.O_DIRECTORY" title="Permalink to this definition">¶</a></dt>

970

971

<code class="descclassname">os.</code><code class="descname">O_NOFOLLOW</code><a class="headerlink" href="#os.O_NOFOLLOW" title="Permalink to this definition">¶</a></dt>

972

973

<code class="descclassname">os.</code><code class="descname">O_NOATIME</code><a class="headerlink" href="#os.O_NOATIME" title="Permalink to this definition">¶</a></dt>

974

<dd>These constants are GNU extensions and not present if they are not defined by

975

the C library.

976

</dd></dl>

977

978

</div>

979

</div>

980

981

<h2>15.1.4. Files and Directories<a class="headerlink" href="#files-and-directories" title="Permalink to this headline">¶</a></h2>

982

983

984

<code class="descclassname">os.</code><code class="descname">access</code>(path, mode)<a class="headerlink" href="#os.access" title="Permalink to this definition">¶</a></dt>

985

<dd>Use the real uid/gid to test for access to path. Note that most operations

986

will use the effective uid/gid, therefore this routine can be used in a

987

suid/sgid environment to test if the invoking user has the specified access to

988

path. mode should be <a class="reference internal" href="#os.F_OK" title="os.F_OK"><code class="xref py py-const docutils literal">F_OK</code></a> to test the existence of path, or it

989

can be the inclusive OR of one or more of <a class="reference internal" href="#os.R_OK" title="os.R_OK"><code class="xref py py-const docutils literal">R_OK</code></a>, <a class="reference internal" href="#os.W_OK" title="os.W_OK"><code class="xref py py-const docutils literal">W_OK</code></a>, and

990

<a class="reference internal" href="#os.X_OK" title="os.X_OK"><code class="xref py py-const docutils literal">X_OK</code></a> to test permissions. Return <a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal">True</code></a> if access is allowed,

991

<a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal">False</code></a> if not. See the Unix man page access(2) for more

992

information.

993

Availability: Unix, Windows.

994

995

Note

996

Using <a class="reference internal" href="#os.access" title="os.access"><code class="xref py py-func docutils literal">access()</code></a> to check if a user is authorized to e.g. open a file

997

before actually doing so using <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal">open()</code></a> creates a security hole,

998

because the user might exploit the short time interval between checking

999

and opening the file to manipulate it. It’s preferable to use <a class="reference internal" href="../glossary.html#term-eafp">EAFP</a>

1000

techniques. For example:

1001

<div class="highlight-python"><div class="highlight"><pre>if os.access("myfile", os.R_OK):

1002

with open("myfile") as fp:

1003

return fp.read()

1004

return "some default data"

1005

</pre></div>

1006

</div>

1007

is better written as:

1008

<div class="last highlight-python"><div class="highlight"><pre>try:

1009

fp = open("myfile")

1010

except IOError as e:

1011

if e.errno == errno.EACCES:

1012

return "some default data"

1013

# Not a permission error.

1014

raise

1015

else:

1016

with fp:

1017

return fp.read()

1018

</pre></div>

1019

</div>

1020

</div>

1021

1022

Note

1023

I/O operations may fail even when <a class="reference internal" href="#os.access" title="os.access"><code class="xref py py-func docutils literal">access()</code></a> indicates that they would

1024

succeed, particularly for operations on network filesystems which may have

1025

permissions semantics beyond the usual POSIX permission-bit model.

1026

</div>

1027

</dd></dl>

1028

1029

1030

1031

1032

<dd>Value to pass as the mode parameter of <a class="reference internal" href="#os.access" title="os.access"><code class="xref py py-func docutils literal">access()</code></a> to test the existence of

1033

path.

1034

</dd></dl>

1035

1036

1037

1038

1039

<dd>Value to include in the mode parameter of <a class="reference internal" href="#os.access" title="os.access"><code class="xref py py-func docutils literal">access()</code></a> to test the

1040

readability of path.

1041

</dd></dl>

1042

1043

1044

1045

1046

1047

writability of path.

1048

</dd></dl>

1049

1050

1051

1052

1053

1054

path can be executed.

1055

</dd></dl>

1056

1057

1058

1059

<code class="descclassname">os.</code><code class="descname">chdir</code>(path)<a class="headerlink" href="#os.chdir" title="Permalink to this definition">¶</a></dt>

1060

<dd>Change the current working directory to path.

1061

Availability: Unix, Windows.

1062

</dd></dl>

1063

1064

1065

1066

<code class="descclassname">os.</code><code class="descname">fchdir</code>(fd)<a class="headerlink" href="#os.fchdir" title="Permalink to this definition">¶</a></dt>

1067

<dd>Change the current working directory to the directory represented by the file

1068

descriptor fd. The descriptor must refer to an opened directory, not an open

1069

file.

1070

Availability: Unix.

1071

1072

New in version 2.3.

1073

</div>

1074

</dd></dl>

1075

1076

1077

1078

<code class="descclassname">os.</code><code class="descname">getcwd</code>()<a class="headerlink" href="#os.getcwd" title="Permalink to this definition">¶</a></dt>

1079

<dd>Return a string representing the current working directory.

1080

Availability: Unix, Windows.

1081

</dd></dl>

1082

1083

1084

1085

<code class="descclassname">os.</code><code class="descname">getcwdu</code>()<a class="headerlink" href="#os.getcwdu" title="Permalink to this definition">¶</a></dt>

1086

<dd>Return a Unicode object representing the current working directory.

1087

Availability: Unix, Windows.

1088

1089

New in version 2.3.

1090

</div>

1091

</dd></dl>

1092

1093

1094

1095

<code class="descclassname">os.</code><code class="descname">chflags</code>(path, flags)<a class="headerlink" href="#os.chflags" title="Permalink to this definition">¶</a></dt>

1096

<dd>Set the flags of path to the numeric flags. flags may take a combination

1097

(bitwise OR) of the following values (as defined in the <a class="reference internal" href="stat.html#module-stat" title="stat: Utilities for interpreting the results of os.stat(), os.lstat() and os.fstat()."><code class="xref py py-mod docutils literal">stat</code></a> module):

1098

1099

<li><a class="reference internal" href="stat.html#stat.UF_NODUMP" title="stat.UF_NODUMP"><code class="xref py py-data docutils literal">stat.UF_NODUMP</code></a></li>

1100

<li><a class="reference internal" href="stat.html#stat.UF_IMMUTABLE" title="stat.UF_IMMUTABLE"><code class="xref py py-data docutils literal">stat.UF_IMMUTABLE</code></a></li>

1101

<li><a class="reference internal" href="stat.html#stat.UF_APPEND" title="stat.UF_APPEND"><code class="xref py py-data docutils literal">stat.UF_APPEND</code></a></li>

1102

<li><a class="reference internal" href="stat.html#stat.UF_OPAQUE" title="stat.UF_OPAQUE"><code class="xref py py-data docutils literal">stat.UF_OPAQUE</code></a></li>

1103

<li><a class="reference internal" href="stat.html#stat.UF_NOUNLINK" title="stat.UF_NOUNLINK"><code class="xref py py-data docutils literal">stat.UF_NOUNLINK</code></a></li>

1104

<li><a class="reference internal" href="stat.html#stat.UF_COMPRESSED" title="stat.UF_COMPRESSED"><code class="xref py py-data docutils literal">stat.UF_COMPRESSED</code></a></li>

1105

<li><a class="reference internal" href="stat.html#stat.UF_HIDDEN" title="stat.UF_HIDDEN"><code class="xref py py-data docutils literal">stat.UF_HIDDEN</code></a></li>

1106

<li><a class="reference internal" href="stat.html#stat.SF_ARCHIVED" title="stat.SF_ARCHIVED"><code class="xref py py-data docutils literal">stat.SF_ARCHIVED</code></a></li>

1107

<li><a class="reference internal" href="stat.html#stat.SF_IMMUTABLE" title="stat.SF_IMMUTABLE"><code class="xref py py-data docutils literal">stat.SF_IMMUTABLE</code></a></li>

1108

<li><a class="reference internal" href="stat.html#stat.SF_APPEND" title="stat.SF_APPEND"><code class="xref py py-data docutils literal">stat.SF_APPEND</code></a></li>

1109

<li><a class="reference internal" href="stat.html#stat.SF_NOUNLINK" title="stat.SF_NOUNLINK"><code class="xref py py-data docutils literal">stat.SF_NOUNLINK</code></a></li>

1110

<li><a class="reference internal" href="stat.html#stat.SF_SNAPSHOT" title="stat.SF_SNAPSHOT"><code class="xref py py-data docutils literal">stat.SF_SNAPSHOT</code></a></li>

1111

</ul>

1112

Availability: Unix.

1113

1114

New in version 2.6.

1115

</div>

1116

</dd></dl>

1117

1118

1119

1120

<code class="descclassname">os.</code><code class="descname">chroot</code>(path)<a class="headerlink" href="#os.chroot" title="Permalink to this definition">¶</a></dt>

1121

<dd>Change the root directory of the current process to path. Availability:

1122

Unix.

1123

1124

New in version 2.2.

1125

</div>

1126

</dd></dl>

1127

1128

1129

1130

<code class="descclassname">os.</code><code class="descname">chmod</code>(path, mode)<a class="headerlink" href="#os.chmod" title="Permalink to this definition">¶</a></dt>

1131

<dd>Change the mode of path to the numeric mode. mode may take one of the

1132

following values (as defined in the <a class="reference internal" href="stat.html#module-stat" title="stat: Utilities for interpreting the results of os.stat(), os.lstat() and os.fstat()."><code class="xref py py-mod docutils literal">stat</code></a> module) or bitwise ORed

1133

combinations of them:

1134

1135

<li><a class="reference internal" href="stat.html#stat.S_ISUID" title="stat.S_ISUID"><code class="xref py py-data docutils literal">stat.S_ISUID</code></a></li>

1136

<li><a class="reference internal" href="stat.html#stat.S_ISGID" title="stat.S_ISGID"><code class="xref py py-data docutils literal">stat.S_ISGID</code></a></li>

1137

<li><a class="reference internal" href="stat.html#stat.S_ENFMT" title="stat.S_ENFMT"><code class="xref py py-data docutils literal">stat.S_ENFMT</code></a></li>

1138

<li><a class="reference internal" href="stat.html#stat.S_ISVTX" title="stat.S_ISVTX"><code class="xref py py-data docutils literal">stat.S_ISVTX</code></a></li>

1139

<li><a class="reference internal" href="stat.html#stat.S_IREAD" title="stat.S_IREAD"><code class="xref py py-data docutils literal">stat.S_IREAD</code></a></li>

1140

<li><a class="reference internal" href="stat.html#stat.S_IWRITE" title="stat.S_IWRITE"><code class="xref py py-data docutils literal">stat.S_IWRITE</code></a></li>

1141

<li><a class="reference internal" href="stat.html#stat.S_IEXEC" title="stat.S_IEXEC"><code class="xref py py-data docutils literal">stat.S_IEXEC</code></a></li>

1142

<li><a class="reference internal" href="stat.html#stat.S_IRWXU" title="stat.S_IRWXU"><code class="xref py py-data docutils literal">stat.S_IRWXU</code></a></li>

1143

<li><a class="reference internal" href="stat.html#stat.S_IRUSR" title="stat.S_IRUSR"><code class="xref py py-data docutils literal">stat.S_IRUSR</code></a></li>

1144

<li><a class="reference internal" href="stat.html#stat.S_IWUSR" title="stat.S_IWUSR"><code class="xref py py-data docutils literal">stat.S_IWUSR</code></a></li>

1145

<li><a class="reference internal" href="stat.html#stat.S_IXUSR" title="stat.S_IXUSR"><code class="xref py py-data docutils literal">stat.S_IXUSR</code></a></li>

1146

<li><a class="reference internal" href="stat.html#stat.S_IRWXG" title="stat.S_IRWXG"><code class="xref py py-data docutils literal">stat.S_IRWXG</code></a></li>

1147

<li><a class="reference internal" href="stat.html#stat.S_IRGRP" title="stat.S_IRGRP"><code class="xref py py-data docutils literal">stat.S_IRGRP</code></a></li>

1148

<li><a class="reference internal" href="stat.html#stat.S_IWGRP" title="stat.S_IWGRP"><code class="xref py py-data docutils literal">stat.S_IWGRP</code></a></li>

1149

<li><a class="reference internal" href="stat.html#stat.S_IXGRP" title="stat.S_IXGRP"><code class="xref py py-data docutils literal">stat.S_IXGRP</code></a></li>

1150

<li><a class="reference internal" href="stat.html#stat.S_IRWXO" title="stat.S_IRWXO"><code class="xref py py-data docutils literal">stat.S_IRWXO</code></a></li>

1151

<li><a class="reference internal" href="stat.html#stat.S_IROTH" title="stat.S_IROTH"><code class="xref py py-data docutils literal">stat.S_IROTH</code></a></li>

1152

<li><a class="reference internal" href="stat.html#stat.S_IWOTH" title="stat.S_IWOTH"><code class="xref py py-data docutils literal">stat.S_IWOTH</code></a></li>

1153

<li><a class="reference internal" href="stat.html#stat.S_IXOTH" title="stat.S_IXOTH"><code class="xref py py-data docutils literal">stat.S_IXOTH</code></a></li>

1154

</ul>

1155

Availability: Unix, Windows.

1156

1157

Note

1158

Although Windows supports <a class="reference internal" href="#os.chmod" title="os.chmod"><code class="xref py py-func docutils literal">chmod()</code></a>, you can only set the file’s read-only

1159

flag with it (via the <code class="docutils literal">stat.S_IWRITE</code> and <code class="docutils literal">stat.S_IREAD</code>

1160

constants or a corresponding integer value). All other bits are

1161

ignored.

1162

</div>

1163

</dd></dl>

1164

1165

1166

1167

<code class="descclassname">os.</code><code class="descname">chown</code>(path, uid, gid)<a class="headerlink" href="#os.chown" title="Permalink to this definition">¶</a></dt>

1168

<dd>Change the owner and group id of path to the numeric uid and gid. To leave

1169

one of the ids unchanged, set it to -1.

1170

Availability: Unix.

1171

</dd></dl>

1172

1173

1174

1175

<code class="descclassname">os.</code><code class="descname">lchflags</code>(path, flags)<a class="headerlink" href="#os.lchflags" title="Permalink to this definition">¶</a></dt>

1176

<dd>Set the flags of path to the numeric flags, like <a class="reference internal" href="#os.chflags" title="os.chflags"><code class="xref py py-func docutils literal">chflags()</code></a>, but do not

1177

follow symbolic links.

1178

Availability: Unix.

1179

1180

New in version 2.6.

1181

</div>

1182

</dd></dl>

1183

1184

1185

1186

<code class="descclassname">os.</code><code class="descname">lchmod</code>(path, mode)<a class="headerlink" href="#os.lchmod" title="Permalink to this definition">¶</a></dt>

1187

<dd>Change the mode of path to the numeric mode. If path is a symlink, this

1188

affects the symlink rather than the target. See the docs for <a class="reference internal" href="#os.chmod" title="os.chmod"><code class="xref py py-func docutils literal">chmod()</code></a>

1189

for possible values of mode.

1190

Availability: Unix.

1191

1192

New in version 2.6.

1193

</div>

1194

</dd></dl>

1195

1196

1197

1198

<code class="descclassname">os.</code><code class="descname">lchown</code>(path, uid, gid)<a class="headerlink" href="#os.lchown" title="Permalink to this definition">¶</a></dt>

1199

<dd>Change the owner and group id of path to the numeric uid and gid. This

1200

function will not follow symbolic links.

1201

Availability: Unix.

1202

1203

New in version 2.3.

1204

</div>

1205

</dd></dl>

1206

1207

1208

1209

<code class="descclassname">os.</code><code class="descname">link</code>(source, link_name)<a class="headerlink" href="#os.link" title="Permalink to this definition">¶</a></dt>

1210

<dd>Create a hard link pointing to source named link_name.

1211

Availability: Unix.

1212

</dd></dl>

1213

1214

1215

1216

<code class="descclassname">os.</code><code class="descname">listdir</code>(path)<a class="headerlink" href="#os.listdir" title="Permalink to this definition">¶</a></dt>

1217

<dd>Return a list containing the names of the entries in the directory given by

1218

path. The list is in arbitrary order. It does not include the special

1219

entries <code class="docutils literal">'.'</code> and <code class="docutils literal">'..'</code> even if they are present in the

1220

directory.

1221

Availability: Unix, Windows.

1222

1223

Changed in version 2.3: On Windows NT/2k/XP and Unix, if path is a Unicode object, the result will be

1224

a list of Unicode objects. Undecodable filenames will still be returned as

1225

string objects.

1226

</div>

1227

</dd></dl>

1228

1229

1230

1231

<code class="descclassname">os.</code><code class="descname">lstat</code>(path)<a class="headerlink" href="#os.lstat" title="Permalink to this definition">¶</a></dt>

1232

<dd>Perform the equivalent of an <code class="xref c c-func docutils literal">lstat()</code> system call on the given path.

1233

Similar to <a class="reference internal" href="#os.stat" title="os.stat"><code class="xref py py-func docutils literal">stat()</code></a>, but does not follow symbolic links. On

1234

platforms that do not support symbolic links, this is an alias for

1235

<a class="reference internal" href="#os.stat" title="os.stat"><code class="xref py py-func docutils literal">stat()</code></a>.

1236

</dd></dl>

1237

1238

1239

1240

<code class="descclassname">os.</code><code class="descname">mkfifo</code>(path[, mode])<a class="headerlink" href="#os.mkfifo" title="Permalink to this definition">¶</a></dt>

1241

<dd>Create a FIFO (a named pipe) named path with numeric mode mode. The default

1242

mode is <code class="docutils literal">0666</code> (octal). The current umask value is first masked out from

1243

the mode.

1244

Availability: Unix.

1245

FIFOs are pipes that can be accessed like regular files. FIFOs exist until they

1246

are deleted (for example with <a class="reference internal" href="#os.unlink" title="os.unlink"><code class="xref py py-func docutils literal">os.unlink()</code></a>). Generally, FIFOs are used as

1247

rendezvous between “client” and “server” type processes: the server opens the

1248

FIFO for reading, and the client opens it for writing. Note that <a class="reference internal" href="#os.mkfifo" title="os.mkfifo"><code class="xref py py-func docutils literal">mkfifo()</code></a>

1249

doesn’t open the FIFO — it just creates the rendezvous point.

1250

</dd></dl>

1251

1252

1253

1254

<code class="descclassname">os.</code><code class="descname">mknod</code>(filename[, mode=0600[, device=0]])<a class="headerlink" href="#os.mknod" title="Permalink to this definition">¶</a></dt>

1255

<dd>Create a filesystem node (file, device special file or named pipe) named

1256

filename. mode specifies both the permissions to use and the type of node to

1257

be created, being combined (bitwise OR) with one of <code class="docutils literal">stat.S_IFREG</code>,

1258

<code class="docutils literal">stat.S_IFCHR</code>, <code class="docutils literal">stat.S_IFBLK</code>,

1259

and <code class="docutils literal">stat.S_IFIFO</code> (those constants are available in <a class="reference internal" href="stat.html#module-stat" title="stat: Utilities for interpreting the results of os.stat(), os.lstat() and os.fstat()."><code class="xref py py-mod docutils literal">stat</code></a>).

1260

For <code class="docutils literal">stat.S_IFCHR</code> and

1261

<code class="docutils literal">stat.S_IFBLK</code>, device defines the newly created device special file (probably using

1262

<a class="reference internal" href="#os.makedev" title="os.makedev"><code class="xref py py-func docutils literal">os.makedev()</code></a>), otherwise it is ignored.

1263

1264

New in version 2.3.

1265

</div>

1266

</dd></dl>

1267

1268

1269

1270

<code class="descclassname">os.</code><code class="descname">major</code>(device)<a class="headerlink" href="#os.major" title="Permalink to this definition">¶</a></dt>

1271

<dd>Extract the device major number from a raw device number (usually the

1272

<code class="xref py py-attr docutils literal">st_dev</code> or <code class="xref py py-attr docutils literal">st_rdev</code> field from <code class="xref c c-type docutils literal">stat</code>).

1273

1274

New in version 2.3.

1275

</div>

1276

</dd></dl>

1277

1278

1279

1280

<code class="descclassname">os.</code><code class="descname">minor</code>(device)<a class="headerlink" href="#os.minor" title="Permalink to this definition">¶</a></dt>

1281

<dd>Extract the device minor number from a raw device number (usually the

1282

1283

1284

New in version 2.3.

1285

</div>

1286

</dd></dl>

1287

1288

1289

1290

<code class="descclassname">os.</code><code class="descname">makedev</code>(major, minor)<a class="headerlink" href="#os.makedev" title="Permalink to this definition">¶</a></dt>

1291

<dd>Compose a raw device number from the major and minor device numbers.

1292

1293

New in version 2.3.

1294

</div>

1295

</dd></dl>

1296

1297

1298

1299

<code class="descclassname">os.</code><code class="descname">mkdir</code>(path[, mode])<a class="headerlink" href="#os.mkdir" title="Permalink to this definition">¶</a></dt>

1300

<dd>Create a directory named path with numeric mode mode. The default mode is

1301

<code class="docutils literal">0777</code> (octal). On some systems, mode is ignored. Where it is used, the

1302

current umask value is first masked out. If the directory already exists,

1303

<a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> is raised.

1304

It is also possible to create temporary directories; see the

1305

<a class="reference internal" href="tempfile.html#module-tempfile" title="tempfile: Generate temporary files and directories."><code class="xref py py-mod docutils literal">tempfile</code></a> module’s <a class="reference internal" href="tempfile.html#tempfile.mkdtemp" title="tempfile.mkdtemp"><code class="xref py py-func docutils literal">tempfile.mkdtemp()</code></a> function.

1306

Availability: Unix, Windows.

1307

</dd></dl>

1308

1309

1310

1311

<code class="descclassname">os.</code><code class="descname">makedirs</code>(path[, mode])<a class="headerlink" href="#os.makedirs" title="Permalink to this definition">¶</a></dt>

1312

<dd>Recursive directory creation function. Like <a class="reference internal" href="#os.mkdir" title="os.mkdir"><code class="xref py py-func docutils literal">mkdir()</code></a>, but makes all

1313

intermediate-level directories needed to contain the leaf directory. Raises an

1314

<a class="reference internal" href="#os.error" title="os.error"><code class="xref py py-exc docutils literal">error</code></a> exception if the leaf directory already exists or cannot be

1315

created. The default mode is <code class="docutils literal">0777</code> (octal). On some systems, mode is

1316

ignored. Where it is used, the current umask value is first masked out.

1317

1318

Note

1319

<a class="reference internal" href="#os.makedirs" title="os.makedirs"><code class="xref py py-func docutils literal">makedirs()</code></a> will become confused if the path elements to create include

1320

<a class="reference internal" href="#os.pardir" title="os.pardir"><code class="xref py py-data docutils literal">os.pardir</code></a>.

1321

</div>

1322

1323

New in version 1.5.2.

1324

</div>

1325

1326

Changed in version 2.3: This function now handles UNC paths correctly.

1327

</div>

1328

</dd></dl>

1329

1330

1331

1332

<code class="descclassname">os.</code><code class="descname">pathconf</code>(path, name)<a class="headerlink" href="#os.pathconf" title="Permalink to this definition">¶</a></dt>

1333

<dd>Return system configuration information relevant to a named file. name

1334

specifies the configuration value to retrieve; it may be a string which is the

1335

name of a defined system value; these names are specified in a number of

1336

standards (POSIX.1, Unix 95, Unix 98, and others). Some platforms define

1337

additional names as well. The names known to the host operating system are

1338

given in the <code class="docutils literal">pathconf_names</code> dictionary. For configuration variables not

1339

included in that mapping, passing an integer for name is also accepted.

1340

1341

specific value for name is not supported by the host system, even if it is

1342

1343

1344

Availability: Unix.

1345

</dd></dl>

1346

1347

1348

1349

<code class="descclassname">os.</code><code class="descname">pathconf_names</code><a class="headerlink" href="#os.pathconf_names" title="Permalink to this definition">¶</a></dt>

1350

<dd>Dictionary mapping names accepted by <a class="reference internal" href="#os.pathconf" title="os.pathconf"><code class="xref py py-func docutils literal">pathconf()</code></a> and <a class="reference internal" href="#os.fpathconf" title="os.fpathconf"><code class="xref py py-func docutils literal">fpathconf()</code></a> to

1351

the integer values defined for those names by the host operating system. This

1352

can be used to determine the set of names known to the system. Availability:

1353

Unix.

1354

</dd></dl>

1355

1356

1357

1358

<code class="descclassname">os.</code><code class="descname">readlink</code>(path)<a class="headerlink" href="#os.readlink" title="Permalink to this definition">¶</a></dt>

1359

<dd>Return a string representing the path to which the symbolic link points. The

1360

result may be either an absolute or relative pathname; if it is relative, it may

1361

be converted to an absolute pathname using <code class="docutils literal">os.path.join(os.path.dirname(path),

1362

result)</code>.

1363

1364

Changed in version 2.6: If the path is a Unicode object the result will also be a Unicode object.

1365

</div>

1366

Availability: Unix.

1367

</dd></dl>

1368

1369

1370

1371

<code class="descclassname">os.</code><code class="descname">remove</code>(path)<a class="headerlink" href="#os.remove" title="Permalink to this definition">¶</a></dt>

1372

<dd>Remove (delete) the file path. If path is a directory, <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> is

1373

raised; see <a class="reference internal" href="#os.rmdir" title="os.rmdir"><code class="xref py py-func docutils literal">rmdir()</code></a> below to remove a directory. This is identical to

1374

the <a class="reference internal" href="#os.unlink" title="os.unlink"><code class="xref py py-func docutils literal">unlink()</code></a> function documented below. On Windows, attempting to

1375

remove a file that is in use causes an exception to be raised; on Unix, the

1376

directory entry is removed but the storage allocated to the file is not made

1377

available until the original file is no longer in use.

1378

Availability: Unix, Windows.

1379

</dd></dl>

1380

1381

1382

1383

<code class="descclassname">os.</code><code class="descname">removedirs</code>(path)<a class="headerlink" href="#os.removedirs" title="Permalink to this definition">¶</a></dt>

1384

<dd>Remove directories recursively. Works like <a class="reference internal" href="#os.rmdir" title="os.rmdir"><code class="xref py py-func docutils literal">rmdir()</code></a> except that, if the

1385

leaf directory is successfully removed, <a class="reference internal" href="#os.removedirs" title="os.removedirs"><code class="xref py py-func docutils literal">removedirs()</code></a> tries to

1386

successively remove every parent directory mentioned in path until an error

1387

is raised (which is ignored, because it generally means that a parent directory

1388

is not empty). For example, <code class="docutils literal">os.removedirs('foo/bar/baz')</code> will first remove

1389

the directory <code class="docutils literal">'foo/bar/baz'</code>, and then remove <code class="docutils literal">'foo/bar'</code> and <code class="docutils literal">'foo'</code> if

1390

they are empty. Raises <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> if the leaf directory could not be

1391

successfully removed.

1392

1393

New in version 1.5.2.

1394

</div>

1395

</dd></dl>

1396

1397

1398

1399

<code class="descclassname">os.</code><code class="descname">rename</code>(src, dst)<a class="headerlink" href="#os.rename" title="Permalink to this definition">¶</a></dt>

1400

<dd>Rename the file or directory src to dst. If dst is a directory,

1401

1402

be replaced silently if the user has permission. The operation may fail on some

1403

Unix flavors if src and dst are on different filesystems. If successful,

1404

the renaming will be an atomic operation (this is a POSIX requirement). On

1405

Windows, if dst already exists, <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> will be raised even if it is a

1406

file; there may be no way to implement an atomic rename when dst names an

1407

existing file.

1408

Availability: Unix, Windows.

1409

</dd></dl>

1410

1411

1412

1413

<code class="descclassname">os.</code><code class="descname">renames</code>(old, new)<a class="headerlink" href="#os.renames" title="Permalink to this definition">¶</a></dt>

1414

<dd>Recursive directory or file renaming function. Works like <a class="reference internal" href="#os.rename" title="os.rename"><code class="xref py py-func docutils literal">rename()</code></a>, except

1415

creation of any intermediate directories needed to make the new pathname good is

1416

attempted first. After the rename, directories corresponding to rightmost path

1417

segments of the old name will be pruned away using <a class="reference internal" href="#os.removedirs" title="os.removedirs"><code class="xref py py-func docutils literal">removedirs()</code></a>.

1418

1419

New in version 1.5.2.

1420

</div>

1421

1422

Note

1423

This function can fail with the new directory structure made if you lack

1424

permissions needed to remove the leaf directory or file.

1425

</div>

1426

</dd></dl>

1427

1428

1429

1430

<code class="descclassname">os.</code><code class="descname">rmdir</code>(path)<a class="headerlink" href="#os.rmdir" title="Permalink to this definition">¶</a></dt>

1431

<dd>Remove (delete) the directory path. Only works when the directory is

1432

empty, otherwise, <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> is raised. In order to remove whole

1433

directory trees, <a class="reference internal" href="shutil.html#shutil.rmtree" title="shutil.rmtree"><code class="xref py py-func docutils literal">shutil.rmtree()</code></a> can be used.

1434

Availability: Unix, Windows.

1435

</dd></dl>

1436

1437

1438

1439

1440

<dd>Perform the equivalent of a <code class="xref c c-func docutils literal">stat()</code> system call on the given path.

1441

(This function follows symlinks; to stat a symlink use <a class="reference internal" href="#os.lstat" title="os.lstat"><code class="xref py py-func docutils literal">lstat()</code></a>.)

1442

The return value is an object whose attributes correspond to the members

1443

of the <code class="xref c c-type docutils literal">stat</code> structure, namely:

1444

1445

<li><code class="xref py py-attr docutils literal">st_mode</code> - protection bits,</li>

1446

<li><code class="xref py py-attr docutils literal">st_ino</code> - inode number,</li>

1447

<li><code class="xref py py-attr docutils literal">st_dev</code> - device,</li>

1448

<li><code class="xref py py-attr docutils literal">st_nlink</code> - number of hard links,</li>

1449

<li><code class="xref py py-attr docutils literal">st_uid</code> - user id of owner,</li>

1450

<li><code class="xref py py-attr docutils literal">st_gid</code> - group id of owner,</li>

1451

<li><code class="xref py py-attr docutils literal">st_size</code> - size of file, in bytes,</li>

1452

<li><code class="xref py py-attr docutils literal">st_atime</code> - time of most recent access,</li>

1453

<li><code class="xref py py-attr docutils literal">st_mtime</code> - time of most recent content modification,</li>

1454

<li><code class="xref py py-attr docutils literal">st_ctime</code> - platform dependent; time of most recent metadata change on

1455

Unix, or the time of creation on Windows)</li>

1456

</ul>

1457

1458

Changed in version 2.3: If <a class="reference internal" href="#os.stat_float_times" title="os.stat_float_times"><code class="xref py py-func docutils literal">stat_float_times()</code></a> returns <code class="docutils literal">True</code>, the time values are floats, measuring

1459

seconds. Fractions of a second may be reported if the system supports that.

1460

See <a class="reference internal" href="#os.stat_float_times" title="os.stat_float_times"><code class="xref py py-func docutils literal">stat_float_times()</code></a> for further discussion.

1461

</div>

1462

On some Unix systems (such as Linux), the following attributes may also be

1463

available:

1464

1465

<li><code class="xref py py-attr docutils literal">st_blocks</code> - number of 512-byte blocks allocated for file</li>

1466

<li><code class="xref py py-attr docutils literal">st_blksize</code> - filesystem blocksize for efficient file system I/O</li>

1467

<li><code class="xref py py-attr docutils literal">st_rdev</code> - type of device if an inode device</li>

1468

<li><code class="xref py py-attr docutils literal">st_flags</code> - user defined flags for file</li>

1469

</ul>

1470

On other Unix systems (such as FreeBSD), the following attributes may be

1471

available (but may be only filled out if root tries to use them):

1472

1473

<li><code class="xref py py-attr docutils literal">st_gen</code> - file generation number</li>

1474

<li><code class="xref py py-attr docutils literal">st_birthtime</code> - time of file creation</li>

1475

</ul>

1476

On RISCOS systems, the following attributes are also available:

1477

1478

<li><code class="xref py py-attr docutils literal">st_ftype</code> (file type)</li>

1479

<li><code class="xref py py-attr docutils literal">st_attrs</code> (attributes)</li>

1480

<li><code class="xref py py-attr docutils literal">st_obtype</code> (object type).</li>

1481

</ul>

1482

1483

Note

1484

The exact meaning and resolution of the <code class="xref py py-attr docutils literal">st_atime</code>,

1485

<code class="xref py py-attr docutils literal">st_mtime</code>, and <code class="xref py py-attr docutils literal">st_ctime</code> attributes depend on the operating

1486

system and the file system. For example, on Windows systems using the FAT

1487

or FAT32 file systems, <code class="xref py py-attr docutils literal">st_mtime</code> has 2-second resolution, and

1488

<code class="xref py py-attr docutils literal">st_atime</code> has only 1-day resolution. See your operating system

1489

documentation for details.

1490

</div>

1491

For backward compatibility, the return value of <a class="reference internal" href="#os.stat" title="os.stat"><code class="xref py py-func docutils literal">stat()</code></a> is also accessible

1492

as a tuple of at least 10 integers giving the most important (and portable)

1493

members of the <code class="xref c c-type docutils literal">stat</code> structure, in the order <code class="xref py py-attr docutils literal">st_mode</code>,

1494

<code class="xref py py-attr docutils literal">st_ino</code>, <code class="xref py py-attr docutils literal">st_dev</code>, <code class="xref py py-attr docutils literal">st_nlink</code>, <code class="xref py py-attr docutils literal">st_uid</code>,

1495

<code class="xref py py-attr docutils literal">st_gid</code>, <code class="xref py py-attr docutils literal">st_size</code>, <code class="xref py py-attr docutils literal">st_atime</code>, <code class="xref py py-attr docutils literal">st_mtime</code>,

1496

<code class="xref py py-attr docutils literal">st_ctime</code>. More items may be added at the end by some implementations.

1497

The standard module <a class="reference internal" href="stat.html#module-stat" title="stat: Utilities for interpreting the results of os.stat(), os.lstat() and os.fstat()."><code class="xref py py-mod docutils literal">stat</code></a> defines functions and constants that are useful

1498

for extracting information from a <code class="xref c c-type docutils literal">stat</code> structure. (On Windows, some

1499

items are filled with dummy values.)

1500

Example:

1501

<div class="highlight-python"><div class="highlight"><pre>>>> import os

1502

>>> statinfo = os.stat('somefile.txt')

1503

>>> statinfo

1504

(33188, 422511, 769, 1, 1032, 100, 926, 1105022698,1105022732, 1105022732)

1505

>>> statinfo.st_size

1506

926

1507

</pre></div>

1508

</div>

1509

Availability: Unix, Windows.

1510

1511

Changed in version 2.2: Added access to values as attributes of the returned object.

1512

</div>

1513

1514

Changed in version 2.5: Added <code class="xref py py-attr docutils literal">st_gen</code> and <code class="xref py py-attr docutils literal">st_birthtime</code>.

1515

</div>

1516

</dd></dl>

1517

1518

1519

1520

<code class="descclassname">os.</code><code class="descname">stat_float_times</code>([newvalue])<a class="headerlink" href="#os.stat_float_times" title="Permalink to this definition">¶</a></dt>

1521

<dd>Determine whether <code class="xref py py-class docutils literal">stat_result</code> represents time stamps as float objects.

1522

If newvalue is <code class="docutils literal">True</code>, future calls to <a class="reference internal" href="#os.stat" title="os.stat"><code class="xref py py-func docutils literal">stat()</code></a> return floats, if it is

1523

<code class="docutils literal">False</code>, future calls return ints. If newvalue is omitted, return the

1524

current setting.

1525

For compatibility with older Python versions, accessing <code class="xref py py-class docutils literal">stat_result</code> as

1526

a tuple always returns integers.

1527

1528

Changed in version 2.5: Python now returns float values by default. Applications which do not work

1529

correctly with floating point time stamps can use this function to restore the

1530

old behaviour.

1531

</div>

1532

The resolution of the timestamps (that is the smallest possible fraction)

1533

depends on the system. Some systems only support second resolution; on these

1534

systems, the fraction will always be zero.

1535

It is recommended that this setting is only changed at program startup time in

1536

the __main__ module; libraries should never change this setting. If an

1537

application uses a library that works incorrectly if floating point time stamps

1538

are processed, this application should turn the feature off until the library

1539

has been corrected.

1540

</dd></dl>

1541

1542

1543

1544

<code class="descclassname">os.</code><code class="descname">statvfs</code>(path)<a class="headerlink" href="#os.statvfs" title="Permalink to this definition">¶</a></dt>

1545

<dd>Perform a <code class="xref c c-func docutils literal">statvfs()</code> system call on the given path. The return value is

1546

an object whose attributes describe the filesystem on the given path, and

1547

correspond to the members of the <code class="xref c c-type docutils literal">statvfs</code> structure, namely:

1548

<code class="xref py py-attr docutils literal">f_bsize</code>, <code class="xref py py-attr docutils literal">f_frsize</code>, <code class="xref py py-attr docutils literal">f_blocks</code>, <code class="xref py py-attr docutils literal">f_bfree</code>,

1549

<code class="xref py py-attr docutils literal">f_bavail</code>, <code class="xref py py-attr docutils literal">f_files</code>, <code class="xref py py-attr docutils literal">f_ffree</code>, <code class="xref py py-attr docutils literal">f_favail</code>,

1550

<code class="xref py py-attr docutils literal">f_flag</code>, <code class="xref py py-attr docutils literal">f_namemax</code>.

1551

For backward compatibility, the return value is also accessible as a tuple whose

1552

values correspond to the attributes, in the order given above. The standard

1553

module <a class="reference internal" href="statvfs.html#module-statvfs" title="statvfs: Constants for interpreting the result of os.statvfs(). (deprecated)"><code class="xref py py-mod docutils literal">statvfs</code></a> defines constants that are useful for extracting

1554

information from a <code class="xref c c-type docutils literal">statvfs</code> structure when accessing it as a sequence;

1555

this remains useful when writing code that needs to work with versions of Python

1556

that don’t support accessing the fields as attributes.

1557

Availability: Unix.

1558

1559

Changed in version 2.2: Added access to values as attributes of the returned object.

1560

</div>

1561

</dd></dl>

1562

1563

1564

1565

<code class="descclassname">os.</code><code class="descname">symlink</code>(source, link_name)<a class="headerlink" href="#os.symlink" title="Permalink to this definition">¶</a></dt>

1566

<dd>Create a symbolic link pointing to source named link_name.

1567

Availability: Unix.

1568

</dd></dl>

1569

1570

1571

1572

<code class="descclassname">os.</code><code class="descname">tempnam</code>([dir[, prefix]])<a class="headerlink" href="#os.tempnam" title="Permalink to this definition">¶</a></dt>

1573

<dd>Return a unique path name that is reasonable for creating a temporary file.

1574

This will be an absolute path that names a potential directory entry in the

1575

directory dir or a common location for temporary files if dir is omitted or

1576

<code class="docutils literal">None</code>. If given and not <code class="docutils literal">None</code>, prefix is used to provide a short prefix

1577

to the filename. Applications are responsible for properly creating and

1578

managing files created using paths returned by <a class="reference internal" href="#os.tempnam" title="os.tempnam"><code class="xref py py-func docutils literal">tempnam()</code></a>; no automatic

1579

cleanup is provided. On Unix, the environment variable <code class="xref std std-envvar docutils literal">TMPDIR</code>

1580

overrides dir, while on Windows <code class="xref std std-envvar docutils literal">TMP</code> is used. The specific

1581

behavior of this function depends on the C library implementation; some aspects

1582

are underspecified in system documentation.

1583

1584

Warning

1585

Use of <a class="reference internal" href="#os.tempnam" title="os.tempnam"><code class="xref py py-func docutils literal">tempnam()</code></a> is vulnerable to symlink attacks; consider using

1586

<a class="reference internal" href="#os.tmpfile" title="os.tmpfile"><code class="xref py py-func docutils literal">tmpfile()</code></a> (section <a class="reference internal" href="#os-newstreams">File Object Creation</a>) instead.

1587

</div>

1588

Availability: Unix, Windows.

1589

</dd></dl>

1590

1591

1592

1593

<code class="descclassname">os.</code><code class="descname">tmpnam</code>()<a class="headerlink" href="#os.tmpnam" title="Permalink to this definition">¶</a></dt>

1594

<dd>Return a unique path name that is reasonable for creating a temporary file.

1595

This will be an absolute path that names a potential directory entry in a common

1596

location for temporary files. Applications are responsible for properly

1597

creating and managing files created using paths returned by <a class="reference internal" href="#os.tmpnam" title="os.tmpnam"><code class="xref py py-func docutils literal">tmpnam()</code></a>; no

1598

automatic cleanup is provided.

1599

1600

Warning

1601

Use of <a class="reference internal" href="#os.tmpnam" title="os.tmpnam"><code class="xref py py-func docutils literal">tmpnam()</code></a> is vulnerable to symlink attacks; consider using

1602

1603

</div>

1604

Availability: Unix, Windows. This function probably shouldn’t be used on

1605

Windows, though: Microsoft’s implementation of <a class="reference internal" href="#os.tmpnam" title="os.tmpnam"><code class="xref py py-func docutils literal">tmpnam()</code></a> always creates a

1606

name in the root directory of the current drive, and that’s generally a poor

1607

location for a temp file (depending on privileges, you may not even be able to

1608

open a file using this name).

1609

</dd></dl>

1610

1611

1612

1613

1614

<dd>The maximum number of unique names that <a class="reference internal" href="#os.tmpnam" title="os.tmpnam"><code class="xref py py-func docutils literal">tmpnam()</code></a> will generate before

1615

reusing names.

1616

</dd></dl>

1617

1618

1619

1620

<code class="descclassname">os.</code><code class="descname">unlink</code>(path)<a class="headerlink" href="#os.unlink" title="Permalink to this definition">¶</a></dt>

1621

<dd>Remove (delete) the file path. This is the same function as

1622

<a class="reference internal" href="#os.remove" title="os.remove"><code class="xref py py-func docutils literal">remove()</code></a>; the <a class="reference internal" href="#os.unlink" title="os.unlink"><code class="xref py py-func docutils literal">unlink()</code></a> name is its traditional Unix

1623

name.

1624

Availability: Unix, Windows.

1625

</dd></dl>

1626

1627

1628

1629

<code class="descclassname">os.</code><code class="descname">utime</code>(path, times)<a class="headerlink" href="#os.utime" title="Permalink to this definition">¶</a></dt>

1630

<dd>Set the access and modified times of the file specified by path. If times

1631

is <code class="docutils literal">None</code>, then the file’s access and modified times are set to the current

1632

time. (The effect is similar to running the Unix program touch on

1633

the path.) Otherwise, times must be a 2-tuple of numbers, of the form

1634

<code class="docutils literal">(atime, mtime)</code> which is used to set the access and modified times,

1635

respectively. Whether a directory can be given for path depends on whether

1636

the operating system implements directories as files (for example, Windows

1637

does not). Note that the exact times you set here may not be returned by a

1638

subsequent <a class="reference internal" href="#os.stat" title="os.stat"><code class="xref py py-func docutils literal">stat()</code></a> call, depending on the resolution with which your

1639

operating system records access and modification times; see <a class="reference internal" href="#os.stat" title="os.stat"><code class="xref py py-func docutils literal">stat()</code></a>.

1640

1641

Changed in version 2.0: Added support for <code class="docutils literal">None</code> for times.

1642

</div>

1643

Availability: Unix, Windows.

1644

</dd></dl>

1645

1646

1647

1648

<code class="descclassname">os.</code><code class="descname">walk</code>(top, topdown=True, onerror=None, followlinks=False)<a class="headerlink" href="#os.walk" title="Permalink to this definition">¶</a></dt>

1649

<dd>Generate the file names in a directory tree by walking the tree

1650

either top-down or bottom-up. For each directory in the tree rooted at directory

1651

top (including top itself), it yields a 3-tuple <code class="docutils literal">(dirpath, dirnames,

1652

filenames)</code>.

1653

dirpath is a string, the path to the directory. dirnames is a list of the

1654

names of the subdirectories in dirpath (excluding <code class="docutils literal">'.'</code> and <code class="docutils literal">'..'</code>).

1655

filenames is a list of the names of the non-directory files in dirpath.

1656

Note that the names in the lists contain no path components. To get a full path

1657

(which begins with top) to a file or directory in dirpath, do

1658

<code class="docutils literal">os.path.join(dirpath, name)</code>.

1659

If optional argument topdown is <code class="docutils literal">True</code> or not specified, the triple for a

1660

directory is generated before the triples for any of its subdirectories

1661

(directories are generated top-down). If topdown is <code class="docutils literal">False</code>, the triple

1662

for a directory is generated after the triples for all of its subdirectories

1663

(directories are generated bottom-up). No matter the value of topdown, the

1664

list of subdirectories is retrieved before the tuples for the directory and

1665

its subdirectories are generated.

1666

When topdown is <code class="docutils literal">True</code>, the caller can modify the dirnames list in-place

1667

(perhaps using <a class="reference internal" href="../reference/simple_stmts.html#del"><code class="xref std std-keyword docutils literal">del</code></a> or slice assignment), and <a class="reference internal" href="#os.walk" title="os.walk"><code class="xref py py-func docutils literal">walk()</code></a> will only

1668

recurse into the subdirectories whose names remain in dirnames; this can be

1669

used to prune the search, impose a specific order of visiting, or even to inform

1670

<a class="reference internal" href="#os.walk" title="os.walk"><code class="xref py py-func docutils literal">walk()</code></a> about directories the caller creates or renames before it resumes

1671

<a class="reference internal" href="#os.walk" title="os.walk"><code class="xref py py-func docutils literal">walk()</code></a> again. Modifying dirnames when topdown is <code class="docutils literal">False</code> has

1672

no effect on the behavior of the walk, because in bottom-up mode the directories

1673

in dirnames are generated before dirpath itself is generated.

1674

By default, errors from the <a class="reference internal" href="#os.listdir" title="os.listdir"><code class="xref py py-func docutils literal">listdir()</code></a> call are ignored. If optional

1675

argument onerror is specified, it should be a function; it will be called with

1676

one argument, an <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> instance. It can report the error to continue

1677

with the walk, or raise the exception to abort the walk. Note that the filename

1678

is available as the <code class="docutils literal">filename</code> attribute of the exception object.

1679

By default, <a class="reference internal" href="#os.walk" title="os.walk"><code class="xref py py-func docutils literal">walk()</code></a> will not walk down into symbolic links that resolve to

1680

directories. Set followlinks to <code class="docutils literal">True</code> to visit directories pointed to by

1681

symlinks, on systems that support them.

1682

1683

New in version 2.6: The followlinks parameter.

1684

</div>

1685

1686

Note

1687

Be aware that setting followlinks to <code class="docutils literal">True</code> can lead to infinite recursion if a

1688

link points to a parent directory of itself. <a class="reference internal" href="#os.walk" title="os.walk"><code class="xref py py-func docutils literal">walk()</code></a> does not keep track of

1689

the directories it visited already.

1690

</div>

1691

1692

Note

1693

If you pass a relative pathname, don’t change the current working directory

1694

between resumptions of <a class="reference internal" href="#os.walk" title="os.walk"><code class="xref py py-func docutils literal">walk()</code></a>. <a class="reference internal" href="#os.walk" title="os.walk"><code class="xref py py-func docutils literal">walk()</code></a> never changes the current

1695

directory, and assumes that its caller doesn’t either.

1696

</div>

1697

This example displays the number of bytes taken by non-directory files in each

1698

directory under the starting directory, except that it doesn’t look under any

1699

CVS subdirectory:

1700

<div class="highlight-python"><div class="highlight"><pre>import os

1701

from os.path import join, getsize

1702

for root, dirs, files in os.walk('python/Lib/email'):

1703

print root, "consumes",

1704

print sum(getsize(join(root, name)) for name in files),

1705

print "bytes in", len(files), "non-directory files"

1706

if 'CVS' in dirs:

1707

dirs.remove('CVS') # don't visit CVS directories

1708

</pre></div>

1709

</div>

1710

In the next example, walking the tree bottom-up is essential: <a class="reference internal" href="#os.rmdir" title="os.rmdir"><code class="xref py py-func docutils literal">rmdir()</code></a>

1711

doesn’t allow deleting a directory before the directory is empty:

1712

<div class="highlight-python"><div class="highlight"><pre># Delete everything reachable from the directory named in "top",

1713

# assuming there are no symbolic links.

1714

# CAUTION: This is dangerous! For example, if top == '/', it

1715

# could delete all your disk files.

1716

import os

1717

for root, dirs, files in os.walk(top, topdown=False):

1718

for name in files:

1719

os.remove(os.path.join(root, name))

1720

for name in dirs:

1721

os.rmdir(os.path.join(root, name))

1722

</pre></div>

1723

</div>

1724

1725

New in version 2.3.

1726

</div>

1727

</dd></dl>

1728

1729

</div>

1730

1731

<h2>15.1.5. Process Management<a class="headerlink" href="#process-management" title="Permalink to this headline">¶</a></h2>

1732

These functions may be used to create and manage processes.

1733

The various <a class="reference internal" href="#os.execl" title="os.execl"><code class="xref py py-func docutils literal">exec*</code></a> functions take a list of arguments for the new

1734

program loaded into the process. In each case, the first of these arguments is

1735

passed to the new program as its own name rather than as an argument a user may

1736

have typed on a command line. For the C programmer, this is the <code class="docutils literal">argv[0]</code>

1737

passed to a program’s <code class="xref c c-func docutils literal">main()</code>. For example, <code class="docutils literal">os.execv('/bin/echo',

1738

['foo', 'bar'])</code> will only print <code class="docutils literal">bar</code> on standard output; <code class="docutils literal">foo</code> will seem

1739

to be ignored.

1740

1741

1742

<code class="descclassname">os.</code><code class="descname">abort</code>()<a class="headerlink" href="#os.abort" title="Permalink to this definition">¶</a></dt>

1743

<dd>Generate a <code class="xref py py-const docutils literal">SIGABRT</code> signal to the current process. On Unix, the default

1744

behavior is to produce a core dump; on Windows, the process immediately returns

1745

an exit code of <code class="docutils literal">3</code>. Be aware that calling this function will not call the

1746

Python signal handler registered for <code class="xref py py-const docutils literal">SIGABRT</code> with

1747

<a class="reference internal" href="signal.html#signal.signal" title="signal.signal"><code class="xref py py-func docutils literal">signal.signal()</code></a>.

1748

Availability: Unix, Windows.

1749

</dd></dl>

1750

1751

1752

1753

<code class="descclassname">os.</code><code class="descname">execl</code>(path, arg0, arg1, ...)<a class="headerlink" href="#os.execl" title="Permalink to this definition">¶</a></dt>

1754

1755

<code class="descclassname">os.</code><code class="descname">execle</code>(path, arg0, arg1, ..., env)<a class="headerlink" href="#os.execle" title="Permalink to this definition">¶</a></dt>

1756

1757

<code class="descclassname">os.</code><code class="descname">execlp</code>(file, arg0, arg1, ...)<a class="headerlink" href="#os.execlp" title="Permalink to this definition">¶</a></dt>

1758

1759

<code class="descclassname">os.</code><code class="descname">execlpe</code>(file, arg0, arg1, ..., env)<a class="headerlink" href="#os.execlpe" title="Permalink to this definition">¶</a></dt>

1760

1761

<code class="descclassname">os.</code><code class="descname">execv</code>(path, args)<a class="headerlink" href="#os.execv" title="Permalink to this definition">¶</a></dt>

1762

1763

<code class="descclassname">os.</code><code class="descname">execve</code>(path, args, env)<a class="headerlink" href="#os.execve" title="Permalink to this definition">¶</a></dt>

1764

1765

<code class="descclassname">os.</code><code class="descname">execvp</code>(file, args)<a class="headerlink" href="#os.execvp" title="Permalink to this definition">¶</a></dt>

1766

1767

<code class="descclassname">os.</code><code class="descname">execvpe</code>(file, args, env)<a class="headerlink" href="#os.execvpe" title="Permalink to this definition">¶</a></dt>

1768

<dd>These functions all execute a new program, replacing the current process; they

1769

do not return. On Unix, the new executable is loaded into the current process,

1770

and will have the same process id as the caller. Errors will be reported as

1771

1772

The current process is replaced immediately. Open file objects and

1773

descriptors are not flushed, so if there may be data buffered

1774

on these open files, you should flush them using

1775

<code class="xref py py-func docutils literal">sys.stdout.flush()</code> or <a class="reference internal" href="#os.fsync" title="os.fsync"><code class="xref py py-func docutils literal">os.fsync()</code></a> before calling an

1776

<a class="reference internal" href="#os.execl" title="os.execl"><code class="xref py py-func docutils literal">exec*</code></a> function.

1777

The “l” and “v” variants of the <a class="reference internal" href="#os.execl" title="os.execl"><code class="xref py py-func docutils literal">exec*</code></a> functions differ in how

1778

command-line arguments are passed. The “l” variants are perhaps the easiest

1779

to work with if the number of parameters is fixed when the code is written; the

1780

individual parameters simply become additional parameters to the <code class="xref py py-func docutils literal">execl*()</code>

1781

functions. The “v” variants are good when the number of parameters is

1782

variable, with the arguments being passed in a list or tuple as the args

1783

parameter. In either case, the arguments to the child process should start with

1784

the name of the command being run, but this is not enforced.

1785

The variants which include a “p” near the end (<a class="reference internal" href="#os.execlp" title="os.execlp"><code class="xref py py-func docutils literal">execlp()</code></a>,

1786

<a class="reference internal" href="#os.execlpe" title="os.execlpe"><code class="xref py py-func docutils literal">execlpe()</code></a>, <a class="reference internal" href="#os.execvp" title="os.execvp"><code class="xref py py-func docutils literal">execvp()</code></a>, and <a class="reference internal" href="#os.execvpe" title="os.execvpe"><code class="xref py py-func docutils literal">execvpe()</code></a>) will use the

1787

<code class="xref std std-envvar docutils literal">PATH</code> environment variable to locate the program file. When the

1788

environment is being replaced (using one of the <a class="reference internal" href="#os.execl" title="os.execl"><code class="xref py py-func docutils literal">exec*e</code></a> variants,

1789

discussed in the next paragraph), the new environment is used as the source of

1790

the <code class="xref std std-envvar docutils literal">PATH</code> variable. The other variants, <a class="reference internal" href="#os.execl" title="os.execl"><code class="xref py py-func docutils literal">execl()</code></a>, <a class="reference internal" href="#os.execle" title="os.execle"><code class="xref py py-func docutils literal">execle()</code></a>,

1791

<a class="reference internal" href="#os.execv" title="os.execv"><code class="xref py py-func docutils literal">execv()</code></a>, and <a class="reference internal" href="#os.execve" title="os.execve"><code class="xref py py-func docutils literal">execve()</code></a>, will not use the <code class="xref std std-envvar docutils literal">PATH</code> variable to

1792

locate the executable; path must contain an appropriate absolute or relative

1793

path.

1794

For <a class="reference internal" href="#os.execle" title="os.execle"><code class="xref py py-func docutils literal">execle()</code></a>, <a class="reference internal" href="#os.execlpe" title="os.execlpe"><code class="xref py py-func docutils literal">execlpe()</code></a>, <a class="reference internal" href="#os.execve" title="os.execve"><code class="xref py py-func docutils literal">execve()</code></a>, and <a class="reference internal" href="#os.execvpe" title="os.execvpe"><code class="xref py py-func docutils literal">execvpe()</code></a> (note

1795

that these all end in “e”), the env parameter must be a mapping which is

1796

used to define the environment variables for the new process (these are used

1797

instead of the current process’ environment); the functions <a class="reference internal" href="#os.execl" title="os.execl"><code class="xref py py-func docutils literal">execl()</code></a>,

1798

<a class="reference internal" href="#os.execlp" title="os.execlp"><code class="xref py py-func docutils literal">execlp()</code></a>, <a class="reference internal" href="#os.execv" title="os.execv"><code class="xref py py-func docutils literal">execv()</code></a>, and <a class="reference internal" href="#os.execvp" title="os.execvp"><code class="xref py py-func docutils literal">execvp()</code></a> all cause the new process to

1799

inherit the environment of the current process.

1800

Availability: Unix, Windows.

1801

</dd></dl>

1802

1803

1804

1805

1806

<dd>Exit the process with status n, without calling cleanup handlers, flushing

1807

stdio buffers, etc.

1808

Availability: Unix, Windows.

1809

1810

Note

1811

The standard way to exit is <code class="docutils literal">sys.exit(n)</code>. <a class="reference internal" href="#os._exit" title="os._exit"><code class="xref py py-func docutils literal">_exit()</code></a> should

1812

normally only be used in the child process after a <a class="reference internal" href="#os.fork" title="os.fork"><code class="xref py py-func docutils literal">fork()</code></a>.

1813

</div>

1814

</dd></dl>

1815

1816

The following exit codes are defined and can be used with <a class="reference internal" href="#os._exit" title="os._exit"><code class="xref py py-func docutils literal">_exit()</code></a>,

1817

although they are not required. These are typically used for system programs

1818

written in Python, such as a mail server’s external command delivery program.

1819

1820

Note

1821

Some of these may not be available on all Unix platforms, since there is some

1822

variation. These constants are defined where they are defined by the underlying

1823

platform.

1824

</div>

1825

1826

1827

1828

<dd>Exit code that means no error occurred.

1829

Availability: Unix.

1830

1831

New in version 2.3.

1832

</div>

1833

</dd></dl>

1834

1835

1836

1837

<code class="descclassname">os.</code><code class="descname">EX_USAGE</code><a class="headerlink" href="#os.EX_USAGE" title="Permalink to this definition">¶</a></dt>

1838

<dd>Exit code that means the command was used incorrectly, such as when the wrong

1839

number of arguments are given.

1840

Availability: Unix.

1841

1842

New in version 2.3.

1843

</div>

1844

</dd></dl>

1845

1846

1847

1848

<code class="descclassname">os.</code><code class="descname">EX_DATAERR</code><a class="headerlink" href="#os.EX_DATAERR" title="Permalink to this definition">¶</a></dt>

1849

<dd>Exit code that means the input data was incorrect.

1850

Availability: Unix.

1851

1852

New in version 2.3.

1853

</div>

1854

</dd></dl>

1855

1856

1857

1858

<code class="descclassname">os.</code><code class="descname">EX_NOINPUT</code><a class="headerlink" href="#os.EX_NOINPUT" title="Permalink to this definition">¶</a></dt>

1859

<dd>Exit code that means an input file did not exist or was not readable.

1860

Availability: Unix.

1861

1862

New in version 2.3.

1863

</div>

1864

</dd></dl>

1865

1866

1867

1868

<code class="descclassname">os.</code><code class="descname">EX_NOUSER</code><a class="headerlink" href="#os.EX_NOUSER" title="Permalink to this definition">¶</a></dt>

1869

<dd>Exit code that means a specified user did not exist.

1870

Availability: Unix.

1871

1872

New in version 2.3.

1873

</div>

1874

</dd></dl>

1875

1876

1877

1878

<code class="descclassname">os.</code><code class="descname">EX_NOHOST</code><a class="headerlink" href="#os.EX_NOHOST" title="Permalink to this definition">¶</a></dt>

1879

<dd>Exit code that means a specified host did not exist.

1880

Availability: Unix.

1881

1882

New in version 2.3.

1883

</div>

1884

</dd></dl>

1885

1886

1887

1888

<code class="descclassname">os.</code><code class="descname">EX_UNAVAILABLE</code><a class="headerlink" href="#os.EX_UNAVAILABLE" title="Permalink to this definition">¶</a></dt>

1889

<dd>Exit code that means that a required service is unavailable.

1890

Availability: Unix.

1891

1892

New in version 2.3.

1893

</div>

1894

</dd></dl>

1895

1896

1897

1898

<code class="descclassname">os.</code><code class="descname">EX_SOFTWARE</code><a class="headerlink" href="#os.EX_SOFTWARE" title="Permalink to this definition">¶</a></dt>

1899

<dd>Exit code that means an internal software error was detected.

1900

Availability: Unix.

1901

1902

New in version 2.3.

1903

</div>

1904

</dd></dl>

1905

1906

1907

1908

<code class="descclassname">os.</code><code class="descname">EX_OSERR</code><a class="headerlink" href="#os.EX_OSERR" title="Permalink to this definition">¶</a></dt>

1909

<dd>Exit code that means an operating system error was detected, such as the

1910

inability to fork or create a pipe.

1911

Availability: Unix.

1912

1913

New in version 2.3.

1914

</div>

1915

</dd></dl>

1916

1917

1918

1919

<code class="descclassname">os.</code><code class="descname">EX_OSFILE</code><a class="headerlink" href="#os.EX_OSFILE" title="Permalink to this definition">¶</a></dt>

1920

<dd>Exit code that means some system file did not exist, could not be opened, or had

1921

some other kind of error.

1922

Availability: Unix.

1923

1924

New in version 2.3.

1925

</div>

1926

</dd></dl>

1927

1928

1929

1930

<code class="descclassname">os.</code><code class="descname">EX_CANTCREAT</code><a class="headerlink" href="#os.EX_CANTCREAT" title="Permalink to this definition">¶</a></dt>

1931

<dd>Exit code that means a user specified output file could not be created.

1932

Availability: Unix.

1933

1934

New in version 2.3.

1935

</div>

1936

</dd></dl>

1937

1938

1939

1940

<code class="descclassname">os.</code><code class="descname">EX_IOERR</code><a class="headerlink" href="#os.EX_IOERR" title="Permalink to this definition">¶</a></dt>

1941

<dd>Exit code that means that an error occurred while doing I/O on some file.

1942

Availability: Unix.

1943

1944

New in version 2.3.

1945

</div>

1946

</dd></dl>

1947

1948

1949

1950

<code class="descclassname">os.</code><code class="descname">EX_TEMPFAIL</code><a class="headerlink" href="#os.EX_TEMPFAIL" title="Permalink to this definition">¶</a></dt>

1951

<dd>Exit code that means a temporary failure occurred. This indicates something

1952

that may not really be an error, such as a network connection that couldn’t be

1953

made during a retryable operation.

1954

Availability: Unix.

1955

1956

New in version 2.3.

1957

</div>

1958

</dd></dl>

1959

1960

1961

1962

<code class="descclassname">os.</code><code class="descname">EX_PROTOCOL</code><a class="headerlink" href="#os.EX_PROTOCOL" title="Permalink to this definition">¶</a></dt>

1963

<dd>Exit code that means that a protocol exchange was illegal, invalid, or not

1964

understood.

1965

Availability: Unix.

1966

1967

New in version 2.3.

1968

</div>

1969

</dd></dl>

1970

1971

1972

1973

<code class="descclassname">os.</code><code class="descname">EX_NOPERM</code><a class="headerlink" href="#os.EX_NOPERM" title="Permalink to this definition">¶</a></dt>

1974

<dd>Exit code that means that there were insufficient permissions to perform the

1975

operation (but not intended for file system problems).

1976

Availability: Unix.

1977

1978

New in version 2.3.

1979

</div>

1980

</dd></dl>

1981

1982

1983

1984

<code class="descclassname">os.</code><code class="descname">EX_CONFIG</code><a class="headerlink" href="#os.EX_CONFIG" title="Permalink to this definition">¶</a></dt>

1985

<dd>Exit code that means that some kind of configuration error occurred.

1986

Availability: Unix.

1987

1988

New in version 2.3.

1989

</div>

1990

</dd></dl>

1991

1992

1993

1994

<code class="descclassname">os.</code><code class="descname">EX_NOTFOUND</code><a class="headerlink" href="#os.EX_NOTFOUND" title="Permalink to this definition">¶</a></dt>

1995

<dd>Exit code that means something like “an entry was not found”.

1996

Availability: Unix.

1997

1998

New in version 2.3.

1999

</div>

2000

</dd></dl>

2001

2002

2003

2004

2005

<dd>Fork a child process. Return <code class="docutils literal">0</code> in the child and the child’s process id in the

2006

parent. If an error occurs <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> is raised.

2007

Note that some platforms including FreeBSD <= 6.3, Cygwin and OS/2 EMX have

2008

known issues when using fork() from a thread.

2009

2010

Warning

2011

See <a class="reference internal" href="ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal">ssl</code></a> for applications that use the SSL module with fork().

2012

</div>

2013

Availability: Unix.

2014

</dd></dl>

2015

2016

2017

2018

<code class="descclassname">os.</code><code class="descname">forkpty</code>()<a class="headerlink" href="#os.forkpty" title="Permalink to this definition">¶</a></dt>

2019

<dd>Fork a child process, using a new pseudo-terminal as the child’s controlling

2020

terminal. Return a pair of <code class="docutils literal">(pid, fd)</code>, where pid is <code class="docutils literal">0</code> in the child, the

2021

new child’s process id in the parent, and fd is the file descriptor of the

2022

master end of the pseudo-terminal. For a more portable approach, use the

2023

<a class="reference internal" href="pty.html#module-pty" title="pty: Pseudo-Terminal Handling for Linux. (Linux)"><code class="xref py py-mod docutils literal">pty</code></a> module. If an error occurs <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> is raised.

2024

Availability: some flavors of Unix.

2025

</dd></dl>

2026

2027

2028

2029

2030

<dd>Send signal sig to the process pid. Constants for the specific signals

2031

available on the host platform are defined in the <a class="reference internal" href="signal.html#module-signal" title="signal: Set handlers for asynchronous events."><code class="xref py py-mod docutils literal">signal</code></a> module.

2032

Windows: The <a class="reference internal" href="signal.html#signal.CTRL_C_EVENT" title="signal.CTRL_C_EVENT"><code class="xref py py-data docutils literal">signal.CTRL_C_EVENT</code></a> and

2033

<a class="reference internal" href="signal.html#signal.CTRL_BREAK_EVENT" title="signal.CTRL_BREAK_EVENT"><code class="xref py py-data docutils literal">signal.CTRL_BREAK_EVENT</code></a> signals are special signals which can

2034

only be sent to console processes which share a common console window,

2035

e.g., some subprocesses. Any other value for sig will cause the process

2036

to be unconditionally killed by the TerminateProcess API, and the exit code

2037

will be set to sig. The Windows version of <a class="reference internal" href="#os.kill" title="os.kill"><code class="xref py py-func docutils literal">kill()</code></a> additionally takes

2038

process handles to be killed.

2039

2040

New in version 2.7: Windows support

2041

</div>

2042

</dd></dl>

2043

2044

2045

2046

<code class="descclassname">os.</code><code class="descname">killpg</code>(pgid, sig)<a class="headerlink" href="#os.killpg" title="Permalink to this definition">¶</a></dt>

2047

<dd>Send the signal sig to the process group pgid.

2048

Availability: Unix.

2049

2050

New in version 2.3.

2051

</div>

2052

</dd></dl>

2053

2054

2055

2056

<code class="descclassname">os.</code><code class="descname">nice</code>(increment)<a class="headerlink" href="#os.nice" title="Permalink to this definition">¶</a></dt>

2057

<dd>Add increment to the process’s “niceness”. Return the new niceness.

2058

Availability: Unix.

2059

</dd></dl>

2060

2061

2062

2063

<code class="descclassname">os.</code><code class="descname">plock</code>(op)<a class="headerlink" href="#os.plock" title="Permalink to this definition">¶</a></dt>

2064

<dd>Lock program segments into memory. The value of op (defined in

2065

<code class="docutils literal"><sys/lock.h></code>) determines which segments are locked.

2066

Availability: Unix.

2067

</dd></dl>

2068

2069

2070

<dt>

2071

<code class="descclassname">os.</code><code class="descname">popen</code>(...)</dt>

2072

<dt>

2073

<code class="descclassname">os.</code><code class="descname">popen2</code>(...)</dt>

2074

<dt>

2075

<code class="descclassname">os.</code><code class="descname">popen3</code>(...)</dt>

2076

<dt>

2077

<code class="descclassname">os.</code><code class="descname">popen4</code>(...)</dt>

2078

<dd>Run child processes, returning opened pipes for communications. These functions

2079

are described in section <a class="reference internal" href="#os-newstreams">File Object Creation</a>.

2080

</dd></dl>

2081

2082

2083

2084

<code class="descclassname">os.</code><code class="descname">spawnl</code>(mode, path, ...)<a class="headerlink" href="#os.spawnl" title="Permalink to this definition">¶</a></dt>

2085

2086

<code class="descclassname">os.</code><code class="descname">spawnle</code>(mode, path, ..., env)<a class="headerlink" href="#os.spawnle" title="Permalink to this definition">¶</a></dt>

2087

2088

<code class="descclassname">os.</code><code class="descname">spawnlp</code>(mode, file, ...)<a class="headerlink" href="#os.spawnlp" title="Permalink to this definition">¶</a></dt>

2089

2090

<code class="descclassname">os.</code><code class="descname">spawnlpe</code>(mode, file, ..., env)<a class="headerlink" href="#os.spawnlpe" title="Permalink to this definition">¶</a></dt>

2091

2092

<code class="descclassname">os.</code><code class="descname">spawnv</code>(mode, path, args)<a class="headerlink" href="#os.spawnv" title="Permalink to this definition">¶</a></dt>

2093

2094

<code class="descclassname">os.</code><code class="descname">spawnve</code>(mode, path, args, env)<a class="headerlink" href="#os.spawnve" title="Permalink to this definition">¶</a></dt>

2095

2096

<code class="descclassname">os.</code><code class="descname">spawnvp</code>(mode, file, args)<a class="headerlink" href="#os.spawnvp" title="Permalink to this definition">¶</a></dt>

2097

2098

<code class="descclassname">os.</code><code class="descname">spawnvpe</code>(mode, file, args, env)<a class="headerlink" href="#os.spawnvpe" title="Permalink to this definition">¶</a></dt>

2099

<dd>Execute the program path in a new process.

2100

(Note that the <a class="reference internal" href="subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal">subprocess</code></a> module provides more powerful facilities for

2101

spawning new processes and retrieving their results; using that module is

2102

preferable to using these functions. Check especially the

2103

<a class="reference internal" href="subprocess.html#subprocess-replacements">Replacing Older Functions with the subprocess Module</a> section.)

2104

If mode is <a class="reference internal" href="#os.P_NOWAIT" title="os.P_NOWAIT"><code class="xref py py-const docutils literal">P_NOWAIT</code></a>, this function returns the process id of the new

2105

process; if mode is <a class="reference internal" href="#os.P_WAIT" title="os.P_WAIT"><code class="xref py py-const docutils literal">P_WAIT</code></a>, returns the process’s exit code if it

2106

exits normally, or <code class="docutils literal">-signal</code>, where signal is the signal that killed the

2107

process. On Windows, the process id will actually be the process handle, so can

2108

be used with the <a class="reference internal" href="#os.waitpid" title="os.waitpid"><code class="xref py py-func docutils literal">waitpid()</code></a> function.

2109

The “l” and “v” variants of the <a class="reference internal" href="#os.spawnl" title="os.spawnl"><code class="xref py py-func docutils literal">spawn*</code></a> functions differ in how

2110

command-line arguments are passed. The “l” variants are perhaps the easiest

2111

to work with if the number of parameters is fixed when the code is written; the

2112

individual parameters simply become additional parameters to the

2113

<code class="xref py py-func docutils literal">spawnl*()</code> functions. The “v” variants are good when the number of

2114

parameters is variable, with the arguments being passed in a list or tuple as

2115

the args parameter. In either case, the arguments to the child process must

2116

start with the name of the command being run.

2117

The variants which include a second “p” near the end (<a class="reference internal" href="#os.spawnlp" title="os.spawnlp"><code class="xref py py-func docutils literal">spawnlp()</code></a>,

2118

<a class="reference internal" href="#os.spawnlpe" title="os.spawnlpe"><code class="xref py py-func docutils literal">spawnlpe()</code></a>, <a class="reference internal" href="#os.spawnvp" title="os.spawnvp"><code class="xref py py-func docutils literal">spawnvp()</code></a>, and <a class="reference internal" href="#os.spawnvpe" title="os.spawnvpe"><code class="xref py py-func docutils literal">spawnvpe()</code></a>) will use the

2119

<code class="xref std std-envvar docutils literal">PATH</code> environment variable to locate the program file. When the

2120

environment is being replaced (using one of the <a class="reference internal" href="#os.spawnl" title="os.spawnl"><code class="xref py py-func docutils literal">spawn*e</code></a> variants,

2121

discussed in the next paragraph), the new environment is used as the source of

2122

the <code class="xref std std-envvar docutils literal">PATH</code> variable. The other variants, <a class="reference internal" href="#os.spawnl" title="os.spawnl"><code class="xref py py-func docutils literal">spawnl()</code></a>,

2123

<a class="reference internal" href="#os.spawnle" title="os.spawnle"><code class="xref py py-func docutils literal">spawnle()</code></a>, <a class="reference internal" href="#os.spawnv" title="os.spawnv"><code class="xref py py-func docutils literal">spawnv()</code></a>, and <a class="reference internal" href="#os.spawnve" title="os.spawnve"><code class="xref py py-func docutils literal">spawnve()</code></a>, will not use the

2124

<code class="xref std std-envvar docutils literal">PATH</code> variable to locate the executable; path must contain an

2125

appropriate absolute or relative path.

2126

For <a class="reference internal" href="#os.spawnle" title="os.spawnle"><code class="xref py py-func docutils literal">spawnle()</code></a>, <a class="reference internal" href="#os.spawnlpe" title="os.spawnlpe"><code class="xref py py-func docutils literal">spawnlpe()</code></a>, <a class="reference internal" href="#os.spawnve" title="os.spawnve"><code class="xref py py-func docutils literal">spawnve()</code></a>, and <a class="reference internal" href="#os.spawnvpe" title="os.spawnvpe"><code class="xref py py-func docutils literal">spawnvpe()</code></a>

2127

(note that these all end in “e”), the env parameter must be a mapping

2128

which is used to define the environment variables for the new process (they are

2129

used instead of the current process’ environment); the functions

2130

<a class="reference internal" href="#os.spawnl" title="os.spawnl"><code class="xref py py-func docutils literal">spawnl()</code></a>, <a class="reference internal" href="#os.spawnlp" title="os.spawnlp"><code class="xref py py-func docutils literal">spawnlp()</code></a>, <a class="reference internal" href="#os.spawnv" title="os.spawnv"><code class="xref py py-func docutils literal">spawnv()</code></a>, and <a class="reference internal" href="#os.spawnvp" title="os.spawnvp"><code class="xref py py-func docutils literal">spawnvp()</code></a> all cause

2131

the new process to inherit the environment of the current process. Note that

2132

keys and values in the env dictionary must be strings; invalid keys or

2133

values will cause the function to fail, with a return value of <code class="docutils literal">127</code>.

2134

As an example, the following calls to <a class="reference internal" href="#os.spawnlp" title="os.spawnlp"><code class="xref py py-func docutils literal">spawnlp()</code></a> and <a class="reference internal" href="#os.spawnvpe" title="os.spawnvpe"><code class="xref py py-func docutils literal">spawnvpe()</code></a> are

2135

equivalent:

2136

<div class="highlight-python"><div class="highlight"><pre>import os

2137

os.spawnlp(os.P_WAIT, 'cp', 'cp', 'index.html', '/dev/null')

2138

2139

L = ['cp', 'index.html', '/dev/null']

2140

os.spawnvpe(os.P_WAIT, 'cp', L, os.environ)

2141

</pre></div>

2142

</div>

2143

Availability: Unix, Windows. <a class="reference internal" href="#os.spawnlp" title="os.spawnlp"><code class="xref py py-func docutils literal">spawnlp()</code></a>, <a class="reference internal" href="#os.spawnlpe" title="os.spawnlpe"><code class="xref py py-func docutils literal">spawnlpe()</code></a>, <a class="reference internal" href="#os.spawnvp" title="os.spawnvp"><code class="xref py py-func docutils literal">spawnvp()</code></a>

2144

and <a class="reference internal" href="#os.spawnvpe" title="os.spawnvpe"><code class="xref py py-func docutils literal">spawnvpe()</code></a> are not available on Windows. <a class="reference internal" href="#os.spawnle" title="os.spawnle"><code class="xref py py-func docutils literal">spawnle()</code></a> and

2145

<a class="reference internal" href="#os.spawnve" title="os.spawnve"><code class="xref py py-func docutils literal">spawnve()</code></a> are not thread-safe on Windows; we advise you to use the

2146

<a class="reference internal" href="subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal">subprocess</code></a> module instead.

2147

2148

New in version 1.6.

2149

</div>

2150

</dd></dl>

2151

2152

2153

2154

<code class="descclassname">os.</code><code class="descname">P_NOWAIT</code><a class="headerlink" href="#os.P_NOWAIT" title="Permalink to this definition">¶</a></dt>

2155

2156

<code class="descclassname">os.</code><code class="descname">P_NOWAITO</code><a class="headerlink" href="#os.P_NOWAITO" title="Permalink to this definition">¶</a></dt>

2157

<dd>Possible values for the mode parameter to the <a class="reference internal" href="#os.spawnl" title="os.spawnl"><code class="xref py py-func docutils literal">spawn*</code></a> family of

2158

functions. If either of these values is given, the <code class="xref py py-func docutils literal">spawn*()</code> functions

2159

will return as soon as the new process has been created, with the process id as

2160

the return value.

2161

Availability: Unix, Windows.

2162

2163

New in version 1.6.

2164

</div>

2165

</dd></dl>

2166

2167

2168

2169

2170

<dd>Possible value for the mode parameter to the <a class="reference internal" href="#os.spawnl" title="os.spawnl"><code class="xref py py-func docutils literal">spawn*</code></a> family of

2171

functions. If this is given as mode, the <code class="xref py py-func docutils literal">spawn*()</code> functions will not

2172

return until the new process has run to completion and will return the exit code

2173

of the process the run is successful, or <code class="docutils literal">-signal</code> if a signal kills the

2174

process.

2175

Availability: Unix, Windows.

2176

2177

New in version 1.6.

2178

</div>

2179

</dd></dl>

2180

2181

2182

2183

<code class="descclassname">os.</code><code class="descname">P_DETACH</code><a class="headerlink" href="#os.P_DETACH" title="Permalink to this definition">¶</a></dt>

2184

2185

<code class="descclassname">os.</code><code class="descname">P_OVERLAY</code><a class="headerlink" href="#os.P_OVERLAY" title="Permalink to this definition">¶</a></dt>

2186

2187

functions. These are less portable than those listed above. <a class="reference internal" href="#os.P_DETACH" title="os.P_DETACH"><code class="xref py py-const docutils literal">P_DETACH</code></a>

2188

is similar to <a class="reference internal" href="#os.P_NOWAIT" title="os.P_NOWAIT"><code class="xref py py-const docutils literal">P_NOWAIT</code></a>, but the new process is detached from the

2189

console of the calling process. If <a class="reference internal" href="#os.P_OVERLAY" title="os.P_OVERLAY"><code class="xref py py-const docutils literal">P_OVERLAY</code></a> is used, the current

2190

process will be replaced; the <code class="xref py py-func docutils literal">spawn*()</code> function will not return.

2191

Availability: Windows.

2192

2193

New in version 1.6.

2194

</div>

2195

</dd></dl>

2196

2197

2198

2199

<code class="descclassname">os.</code><code class="descname">startfile</code>(path[, operation])<a class="headerlink" href="#os.startfile" title="Permalink to this definition">¶</a></dt>

2200

<dd>Start a file with its associated application.

2201

When operation is not specified or <code class="docutils literal">'open'</code>, this acts like double-clicking

2202

the file in Windows Explorer, or giving the file name as an argument to the

2203

start command from the interactive command shell: the file is opened

2204

with whatever application (if any) its extension is associated.

2205

When another operation is given, it must be a “command verb” that specifies

2206

what should be done with the file. Common verbs documented by Microsoft are

2207

<code class="docutils literal">'print'</code> and <code class="docutils literal">'edit'</code> (to be used on files) as well as <code class="docutils literal">'explore'</code> and

2208

<code class="docutils literal">'find'</code> (to be used on directories).

2209

<a class="reference internal" href="#os.startfile" title="os.startfile"><code class="xref py py-func docutils literal">startfile()</code></a> returns as soon as the associated application is launched.

2210

There is no option to wait for the application to close, and no way to retrieve

2211

the application’s exit status. The path parameter is relative to the current

2212

directory. If you want to use an absolute path, make sure the first character

2213

is not a slash (<code class="docutils literal">'/'</code>); the underlying Win32 <code class="xref c c-func docutils literal">ShellExecute()</code> function

2214

doesn’t work if it is. Use the <a class="reference internal" href="os.path.html#os.path.normpath" title="os.path.normpath"><code class="xref py py-func docutils literal">os.path.normpath()</code></a> function to ensure that

2215

the path is properly encoded for Win32.

2216

Availability: Windows.

2217

2218

New in version 2.0.

2219

</div>

2220

2221

New in version 2.5: The operation parameter.

2222

</div>

2223

</dd></dl>

2224

2225

2226

2227

<code class="descclassname">os.</code><code class="descname">system</code>(command)<a class="headerlink" href="#os.system" title="Permalink to this definition">¶</a></dt>

2228

<dd>Execute the command (a string) in a subshell. This is implemented by calling

2229

the Standard C function <code class="xref c c-func docutils literal">system()</code>, and has the same limitations.

2230

Changes to <a class="reference internal" href="sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal">sys.stdin</code></a>, etc. are not reflected in the environment of the

2231

executed command.

2232

On Unix, the return value is the exit status of the process encoded in the

2233

format specified for <a class="reference internal" href="#os.wait" title="os.wait"><code class="xref py py-func docutils literal">wait()</code></a>. Note that POSIX does not specify the meaning

2234

of the return value of the C <code class="xref c c-func docutils literal">system()</code> function, so the return value of

2235

the Python function is system-dependent.

2236

On Windows, the return value is that returned by the system shell after running

2237

command, given by the Windows environment variable <code class="xref std std-envvar docutils literal">COMSPEC</code>: on

2238

command.com systems (Windows 95, 98 and ME) this is always <code class="docutils literal">0</code>; on

2239

cmd.exe systems (Windows NT, 2000 and XP) this is the exit status of

2240

the command run; on systems using a non-native shell, consult your shell

2241

documentation.

2242

The <a class="reference internal" href="subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal">subprocess</code></a> module provides more powerful facilities for spawning new

2243

processes and retrieving their results; using that module is preferable to using

2244

this function. See the

2245

<a class="reference internal" href="subprocess.html#subprocess-replacements">Replacing Older Functions with the subprocess Module</a> section in the <a class="reference internal" href="subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal">subprocess</code></a> documentation

2246

for some helpful recipes.

2247

Availability: Unix, Windows.

2248

</dd></dl>

2249

2250

2251

2252

<code class="descclassname">os.</code><code class="descname">times</code>()<a class="headerlink" href="#os.times" title="Permalink to this definition">¶</a></dt>

2253

<dd>Return a 5-tuple of floating point numbers indicating accumulated (processor

2254

or other) times, in seconds. The items are: user time, system time,

2255

children’s user time, children’s system time, and elapsed real time since a

2256

fixed point in the past, in that order. See the Unix manual page

2257

times(2) or the corresponding Windows Platform API documentation.

2258

On Windows, only the first two items are filled, the others are zero.

2259

Availability: Unix, Windows

2260

</dd></dl>

2261

2262

2263

2264

2265

<dd>Wait for completion of a child process, and return a tuple containing its pid

2266

and exit status indication: a 16-bit number, whose low byte is the signal number

2267

that killed the process, and whose high byte is the exit status (if the signal

2268

number is zero); the high bit of the low byte is set if a core file was

2269

produced.

2270

Availability: Unix.

2271

</dd></dl>

2272

2273

2274

2275

<code class="descclassname">os.</code><code class="descname">waitpid</code>(pid, options)<a class="headerlink" href="#os.waitpid" title="Permalink to this definition">¶</a></dt>

2276

<dd>The details of this function differ on Unix and Windows.

2277

On Unix: Wait for completion of a child process given by process id pid, and

2278

return a tuple containing its process id and exit status indication (encoded as

2279

for <a class="reference internal" href="#os.wait" title="os.wait"><code class="xref py py-func docutils literal">wait()</code></a>). The semantics of the call are affected by the value of the

2280

integer options, which should be <code class="docutils literal">0</code> for normal operation.

2281

If pid is greater than <code class="docutils literal">0</code>, <a class="reference internal" href="#os.waitpid" title="os.waitpid"><code class="xref py py-func docutils literal">waitpid()</code></a> requests status information for

2282

that specific process. If pid is <code class="docutils literal">0</code>, the request is for the status of any

2283

child in the process group of the current process. If pid is <code class="docutils literal">-1</code>, the

2284

request pertains to any child of the current process. If pid is less than

2285

<code class="docutils literal">-1</code>, status is requested for any process in the process group <code class="docutils literal">-pid</code> (the

2286

absolute value of pid).

2287

An <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> is raised with the value of errno when the syscall

2288

returns -1.

2289

On Windows: Wait for completion of a process given by process handle pid, and

2290

return a tuple containing pid, and its exit status shifted left by 8 bits

2291

(shifting makes cross-platform use of the function easier). A pid less than or

2292

equal to <code class="docutils literal">0</code> has no special meaning on Windows, and raises an exception. The

2293

value of integer options has no effect. pid can refer to any process whose

2294

id is known, not necessarily a child process. The <a class="reference internal" href="#os.spawnl" title="os.spawnl"><code class="xref py py-func docutils literal">spawn*</code></a>

2295

functions called with <a class="reference internal" href="#os.P_NOWAIT" title="os.P_NOWAIT"><code class="xref py py-const docutils literal">P_NOWAIT</code></a> return suitable process handles.

2296

</dd></dl>

2297

2298

2299

2300

<code class="descclassname">os.</code><code class="descname">wait3</code>(options)<a class="headerlink" href="#os.wait3" title="Permalink to this definition">¶</a></dt>

2301

<dd>Similar to <a class="reference internal" href="#os.waitpid" title="os.waitpid"><code class="xref py py-func docutils literal">waitpid()</code></a>, except no process id argument is given and a

2302

3-element tuple containing the child’s process id, exit status indication, and

2303

resource usage information is returned. Refer to <a class="reference internal" href="resource.html#module-resource" title="resource: An interface to provide resource usage information on the current process. (Unix)"><code class="xref py py-mod docutils literal">resource</code></a>.<a class="reference internal" href="resource.html#resource.getrusage" title="resource.getrusage"><code class="xref py py-func docutils literal">getrusage()</code></a> for details on resource usage information. The

2304

option argument is the same as that provided to <a class="reference internal" href="#os.waitpid" title="os.waitpid"><code class="xref py py-func docutils literal">waitpid()</code></a> and

2305

<a class="reference internal" href="#os.wait4" title="os.wait4"><code class="xref py py-func docutils literal">wait4()</code></a>.

2306

Availability: Unix.

2307

2308

New in version 2.5.

2309

</div>

2310

</dd></dl>

2311

2312

2313

2314

<code class="descclassname">os.</code><code class="descname">wait4</code>(pid, options)<a class="headerlink" href="#os.wait4" title="Permalink to this definition">¶</a></dt>

2315

2316

process id, exit status indication, and resource usage information is returned.

2317

Refer to <a class="reference internal" href="resource.html#module-resource" title="resource: An interface to provide resource usage information on the current process. (Unix)"><code class="xref py py-mod docutils literal">resource</code></a>.<a class="reference internal" href="resource.html#resource.getrusage" title="resource.getrusage"><code class="xref py py-func docutils literal">getrusage()</code></a> for details on

2318

resource usage information. The arguments to <a class="reference internal" href="#os.wait4" title="os.wait4"><code class="xref py py-func docutils literal">wait4()</code></a> are the same as

2319

those provided to <a class="reference internal" href="#os.waitpid" title="os.waitpid"><code class="xref py py-func docutils literal">waitpid()</code></a>.

2320

Availability: Unix.

2321

2322

New in version 2.5.

2323

</div>

2324

</dd></dl>

2325

2326

2327

2328

<code class="descclassname">os.</code><code class="descname">WNOHANG</code><a class="headerlink" href="#os.WNOHANG" title="Permalink to this definition">¶</a></dt>

2329

<dd>The option for <a class="reference internal" href="#os.waitpid" title="os.waitpid"><code class="xref py py-func docutils literal">waitpid()</code></a> to return immediately if no child process status

2330

is available immediately. The function returns <code class="docutils literal">(0, 0)</code> in this case.

2331

Availability: Unix.

2332

</dd></dl>

2333

2334

2335

2336

<code class="descclassname">os.</code><code class="descname">WCONTINUED</code><a class="headerlink" href="#os.WCONTINUED" title="Permalink to this definition">¶</a></dt>

2337

<dd>This option causes child processes to be reported if they have been continued

2338

from a job control stop since their status was last reported.

2339

Availability: Some Unix systems.

2340

2341

New in version 2.3.

2342

</div>

2343

</dd></dl>

2344

2345

2346

2347

<code class="descclassname">os.</code><code class="descname">WUNTRACED</code><a class="headerlink" href="#os.WUNTRACED" title="Permalink to this definition">¶</a></dt>

2348

<dd>This option causes child processes to be reported if they have been stopped but

2349

their current state has not been reported since they were stopped.

2350

Availability: Unix.

2351

2352

New in version 2.3.

2353

</div>

2354

</dd></dl>

2355

2356

The following functions take a process status code as returned by

2357

<a class="reference internal" href="#os.system" title="os.system"><code class="xref py py-func docutils literal">system()</code></a>, <a class="reference internal" href="#os.wait" title="os.wait"><code class="xref py py-func docutils literal">wait()</code></a>, or <a class="reference internal" href="#os.waitpid" title="os.waitpid"><code class="xref py py-func docutils literal">waitpid()</code></a> as a parameter. They may be

2358

used to determine the disposition of a process.

2359

2360

2361

<code class="descclassname">os.</code><code class="descname">WCOREDUMP</code>(status)<a class="headerlink" href="#os.WCOREDUMP" title="Permalink to this definition">¶</a></dt>

2362

<dd>Return <code class="docutils literal">True</code> if a core dump was generated for the process, otherwise

2363

return <code class="docutils literal">False</code>.

2364

Availability: Unix.

2365

2366

New in version 2.3.

2367

</div>

2368

</dd></dl>

2369

2370

2371

2372

<code class="descclassname">os.</code><code class="descname">WIFCONTINUED</code>(status)<a class="headerlink" href="#os.WIFCONTINUED" title="Permalink to this definition">¶</a></dt>

2373

<dd>Return <code class="docutils literal">True</code> if the process has been continued from a job control stop,

2374

otherwise return <code class="docutils literal">False</code>.

2375

Availability: Unix.

2376

2377

New in version 2.3.

2378

</div>

2379

</dd></dl>

2380

2381

2382

2383

<code class="descclassname">os.</code><code class="descname">WIFSTOPPED</code>(status)<a class="headerlink" href="#os.WIFSTOPPED" title="Permalink to this definition">¶</a></dt>

2384

<dd>Return <code class="docutils literal">True</code> if the process has been stopped, otherwise return

2385

<code class="docutils literal">False</code>.

2386

Availability: Unix.

2387

</dd></dl>

2388

2389

2390

2391

<code class="descclassname">os.</code><code class="descname">WIFSIGNALED</code>(status)<a class="headerlink" href="#os.WIFSIGNALED" title="Permalink to this definition">¶</a></dt>

2392

<dd>Return <code class="docutils literal">True</code> if the process exited due to a signal, otherwise return

2393

<code class="docutils literal">False</code>.

2394

Availability: Unix.

2395

</dd></dl>

2396

2397

2398

2399

<code class="descclassname">os.</code><code class="descname">WIFEXITED</code>(status)<a class="headerlink" href="#os.WIFEXITED" title="Permalink to this definition">¶</a></dt>

2400

<dd>Return <code class="docutils literal">True</code> if the process exited using the exit(2) system call,

2401

otherwise return <code class="docutils literal">False</code>.

2402

Availability: Unix.

2403

</dd></dl>

2404

2405

2406

2407

<code class="descclassname">os.</code><code class="descname">WEXITSTATUS</code>(status)<a class="headerlink" href="#os.WEXITSTATUS" title="Permalink to this definition">¶</a></dt>

2408

<dd>If <code class="docutils literal">WIFEXITED(status)</code> is true, return the integer parameter to the

2409

exit(2) system call. Otherwise, the return value is meaningless.

2410

Availability: Unix.

2411

</dd></dl>

2412

2413

2414

2415

<code class="descclassname">os.</code><code class="descname">WSTOPSIG</code>(status)<a class="headerlink" href="#os.WSTOPSIG" title="Permalink to this definition">¶</a></dt>

2416

<dd>Return the signal which caused the process to stop.

2417

Availability: Unix.

2418

</dd></dl>

2419

2420

2421

2422

<code class="descclassname">os.</code><code class="descname">WTERMSIG</code>(status)<a class="headerlink" href="#os.WTERMSIG" title="Permalink to this definition">¶</a></dt>

2423

<dd>Return the signal which caused the process to exit.

2424

Availability: Unix.

2425

</dd></dl>

2426

2427

</div>

2428

2429

<h2>15.1.6. Miscellaneous System Information<a class="headerlink" href="#miscellaneous-system-information" title="Permalink to this headline">¶</a></h2>

2430

2431

2432

<code class="descclassname">os.</code><code class="descname">confstr</code>(name)<a class="headerlink" href="#os.confstr" title="Permalink to this definition">¶</a></dt>

2433

<dd>Return string-valued system configuration values. name specifies the

2434

configuration value to retrieve; it may be a string which is the name of a

2435

defined system value; these names are specified in a number of standards (POSIX,

2436

Unix 95, Unix 98, and others). Some platforms define additional names as well.

2437

The names known to the host operating system are given as the keys of the

2438

<code class="docutils literal">confstr_names</code> dictionary. For configuration variables not included in that

2439

mapping, passing an integer for name is also accepted.

2440

If the configuration value specified by name isn’t defined, <code class="docutils literal">None</code> is

2441

returned.

2442

2443

specific value for name is not supported by the host system, even if it is

2444

included in <code class="docutils literal">confstr_names</code>, an <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> is raised with

2445

2446

Availability: Unix

2447

</dd></dl>

2448

2449

2450

2451

<code class="descclassname">os.</code><code class="descname">confstr_names</code><a class="headerlink" href="#os.confstr_names" title="Permalink to this definition">¶</a></dt>

2452

<dd>Dictionary mapping names accepted by <a class="reference internal" href="#os.confstr" title="os.confstr"><code class="xref py py-func docutils literal">confstr()</code></a> to the integer values

2453

defined for those names by the host operating system. This can be used to

2454

determine the set of names known to the system.

2455

Availability: Unix.

2456

</dd></dl>

2457

2458

2459

2460

<code class="descclassname">os.</code><code class="descname">getloadavg</code>()<a class="headerlink" href="#os.getloadavg" title="Permalink to this definition">¶</a></dt>

2461

<dd>Return the number of processes in the system run queue averaged over the last

2462

1, 5, and 15 minutes or raises <a class="reference internal" href="exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> if the load average was

2463

unobtainable.

2464

Availability: Unix.

2465

2466

New in version 2.3.

2467

</div>

2468

</dd></dl>

2469

2470

2471

2472

<code class="descclassname">os.</code><code class="descname">sysconf</code>(name)<a class="headerlink" href="#os.sysconf" title="Permalink to this definition">¶</a></dt>

2473

<dd>Return integer-valued system configuration values. If the configuration value

2474

specified by name isn’t defined, <code class="docutils literal">-1</code> is returned. The comments regarding

2475

the name parameter for <a class="reference internal" href="#os.confstr" title="os.confstr"><code class="xref py py-func docutils literal">confstr()</code></a> apply here as well; the dictionary that

2476

provides information on the known names is given by <code class="docutils literal">sysconf_names</code>.

2477

Availability: Unix.

2478

</dd></dl>

2479

2480

2481

2482

<code class="descclassname">os.</code><code class="descname">sysconf_names</code><a class="headerlink" href="#os.sysconf_names" title="Permalink to this definition">¶</a></dt>

2483

<dd>Dictionary mapping names accepted by <a class="reference internal" href="#os.sysconf" title="os.sysconf"><code class="xref py py-func docutils literal">sysconf()</code></a> to the integer values

2484

defined for those names by the host operating system. This can be used to

2485

determine the set of names known to the system.

2486

Availability: Unix.

2487

</dd></dl>

2488

2489

The following data values are used to support path manipulation operations. These

2490

are defined for all platforms.

2491

Higher-level operations on pathnames are defined in the <a class="reference internal" href="os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal">os.path</code></a> module.

2492

2493

2494

<code class="descclassname">os.</code><code class="descname">curdir</code><a class="headerlink" href="#os.curdir" title="Permalink to this definition">¶</a></dt>

2495

<dd>The constant string used by the operating system to refer to the current

2496

directory. This is <code class="docutils literal">'.'</code> for Windows and POSIX. Also available via

2497

<a class="reference internal" href="os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal">os.path</code></a>.

2498

</dd></dl>

2499

2500

2501

2502

<code class="descclassname">os.</code><code class="descname">pardir</code><a class="headerlink" href="#os.pardir" title="Permalink to this definition">¶</a></dt>

2503

<dd>The constant string used by the operating system to refer to the parent

2504

directory. This is <code class="docutils literal">'..'</code> for Windows and POSIX. Also available via

2505

2506

</dd></dl>

2507

2508

2509

2510

2511

<dd>The character used by the operating system to separate pathname components.

2512

This is <code class="docutils literal">'/'</code> for POSIX and <code class="docutils literal">'\\'</code> for Windows. Note that knowing this

2513

is not sufficient to be able to parse or concatenate pathnames — use

2514

<a class="reference internal" href="os.path.html#os.path.split" title="os.path.split"><code class="xref py py-func docutils literal">os.path.split()</code></a> and <a class="reference internal" href="os.path.html#os.path.join" title="os.path.join"><code class="xref py py-func docutils literal">os.path.join()</code></a> — but it is occasionally

2515

useful. Also available via <a class="reference internal" href="os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal">os.path</code></a>.

2516

</dd></dl>

2517

2518

2519

2520

<code class="descclassname">os.</code><code class="descname">altsep</code><a class="headerlink" href="#os.altsep" title="Permalink to this definition">¶</a></dt>

2521

<dd>An alternative character used by the operating system to separate pathname

2522

components, or <code class="docutils literal">None</code> if only one separator character exists. This is set to

2523

<code class="docutils literal">'/'</code> on Windows systems where <code class="docutils literal">sep</code> is a backslash. Also available via

2524

2525

</dd></dl>

2526

2527

2528

2529

<code class="descclassname">os.</code><code class="descname">extsep</code><a class="headerlink" href="#os.extsep" title="Permalink to this definition">¶</a></dt>

2530

<dd>The character which separates the base filename from the extension; for example,

2531

the <code class="docutils literal">'.'</code> in <code class="file docutils literal">os.py</code>. Also available via <a class="reference internal" href="os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal">os.path</code></a>.

2532

2533

New in version 2.2.

2534

</div>

2535

</dd></dl>

2536

2537

2538

2539

<code class="descclassname">os.</code><code class="descname">pathsep</code><a class="headerlink" href="#os.pathsep" title="Permalink to this definition">¶</a></dt>

2540

<dd>The character conventionally used by the operating system to separate search

2541

path components (as in <code class="xref std std-envvar docutils literal">PATH</code>), such as <code class="docutils literal">':'</code> for POSIX or <code class="docutils literal">';'</code> for

2542

Windows. Also available via <a class="reference internal" href="os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal">os.path</code></a>.

2543

</dd></dl>

2544

2545

2546

2547

<code class="descclassname">os.</code><code class="descname">defpath</code><a class="headerlink" href="#os.defpath" title="Permalink to this definition">¶</a></dt>

2548

<dd>The default search path used by <a class="reference internal" href="#os.execl" title="os.execl"><code class="xref py py-func docutils literal">exec*p*</code></a> and

2549

<a class="reference internal" href="#os.spawnl" title="os.spawnl"><code class="xref py py-func docutils literal">spawn*p*</code></a> if the environment doesn’t have a <code class="docutils literal">'PATH'</code>

2550

key. Also available via <a class="reference internal" href="os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal">os.path</code></a>.

2551

</dd></dl>

2552

2553

2554

2555

<code class="descclassname">os.</code><code class="descname">linesep</code><a class="headerlink" href="#os.linesep" title="Permalink to this definition">¶</a></dt>

2556

<dd>The string used to separate (or, rather, terminate) lines on the current

2557

platform. This may be a single character, such as <code class="docutils literal">'\n'</code> for POSIX, or

2558

multiple characters, for example, <code class="docutils literal">'\r\n'</code> for Windows. Do not use

2559

os.linesep as a line terminator when writing files opened in text mode (the

2560

default); use a single <code class="docutils literal">'\n'</code> instead, on all platforms.

2561

</dd></dl>

2562

2563

2564

2565

<code class="descclassname">os.</code><code class="descname">devnull</code><a class="headerlink" href="#os.devnull" title="Permalink to this definition">¶</a></dt>

2566

<dd>The file path of the null device. For example: <code class="docutils literal">'/dev/null'</code> for

2567

POSIX, <code class="docutils literal">'nul'</code> for Windows. Also available via <a class="reference internal" href="os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal">os.path</code></a>.

2568

2569

New in version 2.4.

2570

</div>

2571

</dd></dl>

2572

2573

</div>

2574

2575

<h2>15.1.7. Miscellaneous Functions<a class="headerlink" href="#miscellaneous-functions" title="Permalink to this headline">¶</a></h2>

2576

2577

2578

<code class="descclassname">os.</code><code class="descname">urandom</code>(n)<a class="headerlink" href="#os.urandom" title="Permalink to this definition">¶</a></dt>

2579

<dd>Return a string of n random bytes suitable for cryptographic use.

2580

This function returns random bytes from an OS-specific randomness source. The

2581

returned data should be unpredictable enough for cryptographic applications,

2582

though its exact quality depends on the OS implementation. On a UNIX-like

2583

system this will query <code class="docutils literal">/dev/urandom</code>, and on Windows it will use

2584

<code class="docutils literal">CryptGenRandom()</code>. If a randomness source is not found,

2585

<a class="reference internal" href="exceptions.html#exceptions.NotImplementedError" title="exceptions.NotImplementedError"><code class="xref py py-exc docutils literal">NotImplementedError</code></a> will be raised.

2586

For an easy-to-use interface to the random number generator

2587

provided by your platform, please see <a class="reference internal" href="random.html#random.SystemRandom" title="random.SystemRandom"><code class="xref py py-class docutils literal">random.SystemRandom</code></a>.

2588

2589

New in version 2.4.

2590

</div>

2591

</dd></dl>

2592

2593

</div>

2594

</div>

2595

2596

2597

</div>

2598

</div>

2599

</div>

2600

2601

2602

<h3><a href="../contents.html">Table Of Contents</a></h3>

2603

<ul>

2604

<li><a class="reference internal" href="#">15.1. <code class="docutils literal">os</code> — Miscellaneous operating system interfaces</a><ul>

2605

<li><a class="reference internal" href="#process-parameters">15.1.1. Process Parameters</a></li>

2606

<li><a class="reference internal" href="#file-object-creation">15.1.2. File Object Creation</a></li>

2607

<li><a class="reference internal" href="#file-descriptor-operations">15.1.3. File Descriptor Operations</a><ul>

2608

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