|
Hopefully, this page is exactly what you are looking for, but if not, you can always find further assistance on Unix/Linux Forum!
POPEN(3) FreeBSD Library Functions Manual POPEN(3)
NAME
popen, pclose -- process I/O
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdio.h>
FILE *
popen(const char *command, const char *type);
int
pclose(FILE *stream);
DESCRIPTION
The popen() function ``opens'' a process by creating a bidirectional pipe
forking, and invoking the shell. Any streams opened by previous popen()
calls in the parent process are closed in the new child process. Histor-
ically, popen() was implemented with a unidirectional pipe; hence many
implementations of popen() only allow the type argument to specify read-
ing or writing, not both. Since popen() is now implemented using a bidi-
rectional pipe, the type argument may request a bidirectional data flow.
The type argument is a pointer to a null-terminated string which must be
`r' for reading, `w' for writing, or `r+' for reading and writing.
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 -c
flag; interpretation, if any, is performed by the shell.
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, read-
ing 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).
RETURN VALUES
The popen() function returns NULL if the fork(2) or pipe(2) calls fail,
or if it cannot allocate memory.
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.
ERRORS
The popen() function does not reliably set errno.
SEE ALSO
sh(1), fork(2), pipe(2), wait4(2), fclose(3), fflush(3), fopen(3),
stdio(3), system(3)
HISTORY
A popen() and a pclose() function appeared in Version 7 AT&T UNIX.
Bidirectional functionality was added in FreeBSD 2.2.6.
BUGS
Since the standard input of a command opened for reading shares its seek
offset with the process that called popen(), if the original process has
done a buffered read, the command's input position may not be as
expected. Similarly, the output from a command opened for writing may
become intermingled with that of the original process. The latter can be
avoided by calling fflush(3) before popen().
Failure to execute the shell is indistinguishable from the shell's fail-
ure 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).
FreeBSD 6.2 May 3, 1995 FreeBSD 6.2
Man(1) output converted with
man2html and wrapped by fishsponge
This page was generated on Fri Sep 21 07:56:52 BST 2007
|
Your favourite pages:
No pages logged yet.
Trying to save cookie... Top 10 most popular pages:
svn man page (5400 hits)
(FreeBSD 6.2)
sqlite3 man page (5399 hits)
(openSUSE 10.2)
adv_cap_autoneg man page (4903 hits)
(Solaris 10 11_06)
CPAN man page (4638 hits)
(Suse Linux 10.1)
ssh man page (4358 hits)
(Suse Linux 10.1)
ssh-socks5-proxy-connect man page (3024 hits)
(Solaris 10 11_06)
netcat man page (2831 hits)
(Suse Linux 10.1)
signal man page (2740 hits)
(Suse Linux 10.1)
pprosetup man page (2531 hits)
(Solaris 10 11_06)
startproc man page (2526 hits)
(Suse Linux 10.1)
|
Man Pages 
