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/* Creation of subprocesses, communicating via pipes.
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Copyright (C) 2001-2003 Free Software Foundation, Inc.
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Written by Bruno Haible <haible@clisp.cons.org>, 2001.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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#include <sys/types.h>
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/* All these functions create a subprocess and don't wait for its termination.
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They return the process id of the subprocess. They also return in fd[]
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one or two file descriptors for communication with the subprocess.
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If the subprocess creation fails: if exit_on_error is true, the main
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process exits with an error message; otherwise, an error message is given
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if null_stderr is false, then -1 is returned and fd[] remain uninitialized.
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After finishing communication, the caller should call wait_subprocess()
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to get rid of the subprocess in the process table.
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If slave_process is true, the child process will be terminated when its
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creator receives a catchable fatal signal or exits normally. If
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slave_process is false, the child process will continue running in this
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case, until it is lucky enough to attempt to communicate with its creator
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and thus get a SIGPIPE signal.
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If exit_on_error is false, a child process id of -1 should be treated the
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same way as a subprocess which accepts no input, produces no output and
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terminates with exit code 127. Why? Some errors during posix_spawnp()
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cause the function posix_spawnp() to return an error code; some other
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errors cause the subprocess to exit with return code 127. It is
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implementation dependent which error is reported which way. The caller
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must treat both cases as equivalent.
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It is recommended that no signal is blocked or ignored (i.e. have a
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signal handler with value SIG_IGN) while any of these functions is called.
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The reason is that child processes inherit the mask of blocked signals
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from their parent (both through posix_spawn() and fork()/exec());
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likewise, signals ignored in the parent are also ignored in the child
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(except possibly for SIGCHLD). And POSIX:2001 says [in the description
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"it should be noted that many existing applications wrongly
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assume that they start with certain signals set to the default
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action and/or unblocked. In particular, applications written
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with a simpler signal model that does not include blocking of
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signals, such as the one in the ISO C standard, may not behave
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properly if invoked with some signals blocked. Therefore, it is
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best not to block or ignore signals across execs without explicit
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reason to do so, and especially not to block signals across execs
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of arbitrary (not closely co-operating) programs." */
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/* Open a pipe for output to a child process.
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* The child's stdout goes to a file.
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* parent -> fd[0] -> STDIN_FILENO -> child
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extern pid_t create_pipe_out (const char *progname,
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const char *prog_path, char **prog_argv,
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const char *prog_stdout, bool null_stderr,
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bool slave_process, bool exit_on_error,
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/* Open a pipe for input from a child process.
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* The child's stdin comes from a file.
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* parent <- fd[0] <- STDOUT_FILENO <- child
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extern pid_t create_pipe_in (const char *progname,
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const char *prog_path, char **prog_argv,
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const char *prog_stdin, bool null_stderr,
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bool slave_process, bool exit_on_error,
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/* Open a bidirectional pipe.
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* parent -> fd[1] -> STDIN_FILENO -> child
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* parent <- fd[0] <- STDOUT_FILENO <- child
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extern pid_t create_pipe_bidi (const char *progname,
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const char *prog_path, char **prog_argv,
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bool slave_process, bool exit_on_error,
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/* The name of the "always silent" device. */
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#if defined _MSC_VER || defined __MINGW32__
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/* Native Woe32 API. */
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# define DEV_NULL "NUL"
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# define DEV_NULL "/dev/null"