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<p><a name="__index__"></a></p>
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<li><a href="#name">NAME</a></li>
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<li><a href="#description">DESCRIPTION</a></li>
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<li><a href="#core_functions">CORE FUNCTIONS</a></li>
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<li><a href="#utility_functions">UTILITY FUNCTIONS</a></li>
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<li><a href="#author">AUTHOR</a></li>
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<h1><a name="name">NAME</a></h1>
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<p>librrd - RRD library functions</p>
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<h1><a name="description">DESCRIPTION</a></h1>
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<p><strong>librrd</strong> contains most of the functionality in <strong>RRDTool</strong>. The command
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line utilities and language bindings are often just wrappers around the
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code contained in <strong>librrd</strong>.</p>
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<p>This manual page documents the <strong>librrd</strong> API.</p>
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<p><strong>NOTE:</strong> This document is a work in progress, and should be considered
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incomplete as long as this warning persists. For more information about
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the <strong>librrd</strong> functions, always consult the source code.</p>
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<h1><a name="core_functions">CORE FUNCTIONS</a></h1>
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<dt><strong><a name="rrd_dump_cb_r" class="item"><strong>rrd_dump_cb_r(char *filename, int opt_header, rrd_output_callback_t cb, void *user)</strong></a></strong></dt>
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<p>In some situations it is necessary to get the output of <code>rrd_dump</code> without
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writing it to a file or the standard output. In such cases an application
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can ask <strong>rrd_dump_cb_r</strong> to call an user-defined function each time there
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is output to be stored somewhere. This can be used, to e.g. directly feed
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an XML parser with the dumped output or transfer the resulting string
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<p>The arguments for <strong>rrd_dump_cb_r</strong> are the same as for <strong>rrd_dump_opt_r</strong>
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except that the output filename parameter is replaced by the user-defined
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callback function and an additional parameter for the callback function
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that is passed untouched, i.e. to store information about the callback state
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needed for the user-defined callback to function properly.</p>
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<p>Recent versions of <strong>rrd_dump_opt_r</strong> internally use this callback mechanism
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to write their output to the file provided by the user.</p>
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size_t rrd_dump_opt_cb_fileout(
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return fwrite(data, 1, len, (FILE *)user);
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<p>The associated call for <strong>rrd_dump_cb_r</strong> looks like</p>
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res = rrd_dump_cb_r(filename, opt_header,
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rrd_dump_opt_cb_fileout, (void *)out_file);</pre>
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<p>where the last parameter specifies the file handle <strong>rrd_dump_opt_cb_fileout</strong>
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should write to. There's no specific condition for the callback to detect
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when it is called for the first time, nor for the last time. If you require
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this for initialization and cleanup you should do those tasks before and
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after calling <strong>rrd_dump_cr_r</strong> respectively.</p>
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<h1><a name="utility_functions">UTILITY FUNCTIONS</a></h1>
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<dt><strong><a name="rrd_random" class="item"><strong>rrd_random()</strong></a></strong></dt>
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<p>Generates random numbers just like <code>random()</code>. This further ensures that
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the random number generator is seeded exactly once per process.</p>
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<dt><strong><a name="rrd_add_ptr" class="item"><strong>rrd_add_ptr(void ***dest, size_t *dest_size, void *src)</strong></a></strong></dt>
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<p>Dynamically resize the array pointed to by <code>dest</code>. <code>dest_size</code> is a
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pointer to the current size of <code>dest</code>. Upon successful <code>realloc()</code>, the
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<code>dest_size</code> is incremented by 1 and the <code>src</code> pointer is stored at the
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end of the new <code>dest</code>. Returns 1 on success, 0 on failure.</p>
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type *elem = "whatever";
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if (!rrd_add_ptr(&arr, &arr_size, elem))
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handle_failure();</pre>
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<dt><strong><a name="rrd_add_strdup" class="item"><strong>rrd_add_strdup(char ***dest, size_t *dest_size, char *src)</strong></a></strong></dt>
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<p>Like <a href="#rrd_add_ptr"><code>rrd_add_ptr</code></a>, except adds a <code>strdup</code> of the source string.</p>
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size_t arr_size = NULL;
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char *str = "example text";
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if (!rrd_add_strdup(&arr, &arr_size, str))
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handle_failure();</pre>
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<dt><strong><a name="rrd_free_ptrs" class="item"><strong>rrd_free_ptrs(void ***src, size_t *cnt)</strong></a></strong></dt>
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<p>Free an array of pointers allocated by <a href="#rrd_add_ptr"><code>rrd_add_ptr</code></a> or
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<a href="#rrd_add_strdup"><code>rrd_add_strdup</code></a>. Also frees the array pointer itself. On return, the
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source pointer will be NULL and the count will be zero.</p>
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/* created as above */
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rrd_free_ptrs(&arr, &arr_size);
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/* here, arr == NULL && arr_size == 0 */</pre>
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<dt><strong><a name="rrd_mkdir_p" class="item"><strong>rrd_mkdir_p(const char *pathname, mode_t mode)</strong></a></strong></dt>
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<p>Create the directory named <code>pathname</code> including all of its parent
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directories (similar to <code>mkdir -p</code> on the command line - see <em>mkdir(1)</em> for
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more information). The argument <code>mode</code> specifies the permissions to use. It
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is modified by the process's <code>umask</code>. See <em>mkdir(2)</em> for more details.</p>
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<p>The function returns 0 on success, a negative value else. In case of an error,
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<code>errno</code> is set accordingly. Aside from the errors documented in <em>mkdir(2)</em>,
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the function may fail with the following errors:</p>
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<dt><strong><a name="einval" class="item"><strong>EINVAL</strong></a></strong></dt>
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<p><code>pathname</code> is <code>NULL</code> or the empty string.</p>
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<dt><strong><a name="enomem" class="item"><strong>ENOMEM</strong></a></strong></dt>
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<p>Insufficient memory was available.</p>
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<dt><strong><a name="stat" class="item"><strong>any error returned by <a href="#stat">stat(2)</a></strong></a></strong></dt>
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<p>In contrast to <em>mkdir(2)</em>, the function does <strong>not</strong> fail if <code>pathname</code>
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already exists and is a directory.</p>
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<h1><a name="author">AUTHOR</a></h1>
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<p>RRD Contributors <<a href="mailto:rrd-developers@lists.oetiker.ch">rrd-developers@lists.oetiker.ch</a>></p>
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