POPEN(3)

NAME
popen, pclose - tie a stream to a command string

SYNOPSIS

#include <stdio.h>

FILE *popen(const char *s, const char *mode);

int pclose(FILE *f);

DESCRIPTION

Use popen to create a stream to a child process executing a command string *s as processed by /bin/sh on your system. The argument mode must start with either `r', where the stream reads from the child's stdout, or `w', where the stream writes to the child's stdin. As an extension, mode may also contain `e' to set the close-on-exec bit of the parent's file descriptor. The stream created by popen must be closed by pclose to avoid resource leaks.

Streams created by prior calls to popen are not visible in subsequent popen children, regardless of the close-on-exec bit.

Use ``system(NULL)'' to test whether your system has /bin/sh available.

RETURNS

popen returns a file stream opened with the specified mode, or NULL if a child process could not be created. pclose returns -1 if the stream was not created by popen or if the application used wait or similar to steal the status; otherwise it returns the exit status of the child which can be interpreted in the same manner as a status obtained by waitpid.

PORTABILITY

POSIX.2 requires popen and pclose, but only specifies a mode of just r or w. Where sh is found is left unspecified.

Supporting OS subroutines required: _exit, _execve, _fork_r, _wait_r, pipe, fcntl, sbrk.

AUTHORS

Steve Chamberlain
    Author.

Roland Pesch
    Author.

Red Hat Support

Jeff Johnston
    Author.

COPYRIGHT

This file documents the ANSI C library.

Copyright (C) 1992, 1993, 1994-2014 Red Hat, Inc.

libc includes software developed by the University of California, Berkeley and its contributors.

libc includes software developed by Martin Jackson, Graham Haley and Steve Chamberlain of Tadpole Technology and released to Cygnus.

libc uses floating-point conversion software developed at AT&T, which includes this copyright information:

The author of this software is David M. Gay.

Copyright (c) 1991 by AT&T.

Permission to use, copy, modify, and distribute this software for any purpose without fee is hereby granted, provided that this entire notice is included in all copies of any software which is or includes a copy or modification of this software and in all copies of the supporting documentation for such software.

THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED WARRANTY. IN PARTICULAR, NEITHER THE AUTHOR NOR AT&T MAKES ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.

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Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, subject to the terms of the GNU General Public License, which includes the provision that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

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