pipe — create pipe
#include <unistd.h>
int
pipe( |
int | filedes[2]) ; |
pipe
() 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.
On success, zero is returned. On error, −1 is
returned, and errno
is set
appropriately.
filedes
is
not valid.
Too many file descriptors are in use by the process.
The system limit on the total number of open files has been reached.
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); } }
fork(2), read(2), socketpair(2), write(2), popen(3), pipe(7)
Copyright (c) 1992 Drew Eckhardt (drewcs.colorado.edu), March 28, 1992 Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. Modified by Michael Haardt <michaelmoria.de> Modified 1993-07-23 by Rik Faith <faithcs.unc.edu> Modified 1996-10-22 by Eric S. Raymond <esrthyrsus.com> Modified 2004-06-17 by Michael Kerrisk <mtk-manpagesgmx.net> |