mirror of https://github.com/mkerrisk/man-pages
133 lines
3.6 KiB
Groff
133 lines
3.6 KiB
Groff
.\" Hey Emacs! This file is -*- nroff -*- source.
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.\"
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.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" Modified by Michael Haardt <michael@moria.de>
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.\" Modified 1993-07-23 by Rik Faith <faith@cs.unc.edu>
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.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
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.\" Modified 2004-06-17 by Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.TH PIPE 2 2004-06-17 "Linux" "Linux Programmer's Manual"
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.SH NAME
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pipe \- create pipe
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.SH SYNOPSIS
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.B #include <unistd.h>
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.sp
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.BI "int pipe(int " filedes "[2]);"
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.SH DESCRIPTION
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.BR pipe ()
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creates a pair of file descriptors, pointing to a pipe inode, and places
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them in the array pointed to by
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.IR filedes .
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.I filedes[0]
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is for reading,
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.I filedes[1]
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is for writing.
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.SH "RETURN VALUE"
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On success, zero is returned.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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.TP
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.B EFAULT
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.I filedes
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is not valid.
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.TP
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.B EMFILE
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Too many file descriptors are in use by the process.
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.TP
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.B ENFILE
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The system limit on the total number of open files has been reached.
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.SH "CONFORMING TO"
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POSIX.1-2001.
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.SH EXAMPLE
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.\" fork.2 refers to this example program.
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The following program creates a pipe, and then
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.BR fork (2)s
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to create a child process.
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After the
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.BR fork (2),
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each process closes the descriptors that it doesn't need for the pipe
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(see
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.BR pipe (7)).
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The parent then writes the string contained in the program's
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command-line argument to the pipe,
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and the child reads this string a byte at a time from the pipe
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and echoes it on standard output.
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.nf
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#include <sys/wait.h>
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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int
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main(int argc, char *argv[])
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{
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int pfd[2];
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pid_t cpid;
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char buf;
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assert(argc == 2);
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if (pipe(pfd) == \-1) {
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perror("pipe");
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exit(EXIT_FAILURE);
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}
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cpid = fork();
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if (cpid == \-1) {
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perror("fork");
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exit(EXIT_FAILURE);
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}
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if (cpid == 0) { /* Child reads from pipe */
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close(pfd[1]); /* Close unused write end */
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while (read(pfd[0], &buf, 1) > 0)
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write(STDOUT_FILENO, &buf, 1);
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write(STDOUT_FILENO, "\\n", 1);
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close(pfd[0]);
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_exit(EXIT_SUCCESS);
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} else { /* Parent writes argv[1] to pipe */
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close(pfd[0]); /* Close unused read end */
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write(pfd[1], argv[1], strlen(argv[1]));
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close(pfd[1]); /* Reader will see EOF */
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wait(NULL); /* Wait for child */
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exit(EXIT_SUCCESS);
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}
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}
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.fi
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.SH "SEE ALSO"
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.BR fork (2),
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.BR read (2),
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.BR socketpair (2),
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.BR write (2),
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.BR popen (3),
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.BR pipe (7)
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