Manual page for POPEN(3)
popen, pclose - initiate I/O to/from a process
SYNOPSIS
#include <stdio.h>
FILE
*popen(command, type)
char *command, *type;
pclose(stream)
FILE
*stream;
DESCRIPTION
The arguments to
popen
are pointers to null-terminated strings containing respectively a
shell command line and an I/O mode, either "r" for reading or "w" for
writing. It creates a pipe between the calling process and
the command to be executed. The value returned is a stream pointer that
can be used (as appropriate) to write to the standard input
of the command or read from its standard output.
A stream opened by
popen
should be closed by
pclose,
which waits for the associated process to terminate
and returns the exit status of the command.
Because open files are shared, a type "r" command may be used as an input
filter, and a type "w" as an output filter.
SEE ALSO
pipe(2),
fopen(3S),
fclose(3S),
system(3),
wait(2),
sh(1)
DIAGNOSTICS
Popen
returns a null pointer if files or processes cannot be created, or the shell
cannot be accessed.
Pclose
returns -1 if
stream
is not associated with a `popened' command.
BUGS
Buffered reading before opening an input filter
may leave the standard input of that filter mispositioned.
Similar problems with an output filter may be
forestalled by careful buffer flushing, for instance, with
fflush,
see
fclose.3s
Popen
always calls
sh,
never calls
csh.
Created by unroff & hp-tools.
© somebody (See intro for details). All Rights Reserved.
Last modified 11/5/97
