PIPE(2) Linux Programmer's Manual PIPE(2)NAMEpipe - create pipeSYNOPSIS
#include <unistd.h>
int pipe(int filedes[2]);
DESCRIPTIONpipe() creates a pair of file descriptors, pointing to a pipe inode,
and places them in the array pointed to by filedes. filedes[0] is for
reading, filedes[1] is for writing.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is
set appropriately.
ERRORS
EFAULT filedes is not valid.
EMFILE Too many file descriptors are in use by the process.
ENFILE The system limit on the total number of open files has been
reached.
CONFORMING TO
POSIX.1-2001.
EXAMPLE
The following program creates a pipe, and then fork(2)s to create a
child process. After the fork(2), each process closes the descriptors
that it doesn't need for the pipe (see pipe(7)). The parent then
writes the string contained in the program's command-line argument to
the pipe, and the child reads this string a byte at a time from the
pipe and echoes it on standard output.
#include <sys/wait.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
int
main(int argc, char *argv[])
{
int pfd[2];
pid_t cpid;
char buf;
assert(argc == 2);
if (pipe(pfd) == -1) { perror("pipe"); exit(EXIT_FAILURE); }
cpid = fork();
if (cpid == -1) { perror("fork"); exit(EXIT_FAILURE); }
if (cpid == 0) { /* Child reads from pipe */
close(pfd[1]); /* Close unused write end */
while (read(pfd[0], &buf, 1) > 0)
write(STDOUT_FILENO, &buf, 1);
write(STDOUT_FILENO, "\n", 1);
close(pfd[0]);
_exit(EXIT_SUCCESS);
} else { /* Parent writes argv[1] to pipe */
close(pfd[0]); /* Close unused read end */
write(pfd[1], argv[1], strlen(argv[1]));
close(pfd[1]); /* Reader will see EOF */
wait(NULL); /* Wait for child */
exit(EXIT_SUCCESS);
}
}
SEE ALSOfork(2), read(2), socketpair(2), write(2), popen(3), pipe(7)Linux 2.6.7 2004-06-17 PIPE(2)
