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#include <stdio.h>
A letter ‘e’ may be appended to that to request that the underlying file descriptor be set close-on-exec.
The
command
argument is a pointer to a null-terminated string
containing a shell command line.
This command is passed to
/bin/sh
using the
The return value from popen() is a normal standard I/O stream in all respects save that it must be closed with pclose() rather than fclose(). Writing to such a stream writes to the standard input of the command; the command's standard output is the same as that of the process that called popen(), unless this is altered by the command itself. Conversely, reading from a "popened" stream reads the command's standard output, and the command's standard input is the same as that of the process that called popen().
Note that output popen() streams are fully buffered by default.
The pclose() function waits for the associated process to terminate and returns the exit status of the command as returned by wait4(2).
The pclose() function returns -1 if stream is not associated with a "popened" command, if stream already "pclosed", or if wait4(2) returns an error.
Bidirectional functionality was added in FreeBSD 2.2.6 .
Failure to execute the shell is indistinguishable from the shell's failure to execute command, or an immediate exit of the command. The only hint is an exit status of 127.
The popen() function always calls sh(1), never calls csh(1).
POPEN (3) | May 20, 2013 |
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