pipe - phpMan

PIPE(2)                    Linux Programmer's Manual                   PIPE(2)



NAME
       pipe - create pipe

SYNOPSIS
       #include <unistd.h>

       int pipe(int filedes[2]);

DESCRIPTION
       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.

RETURN VALUE
       On success, zero is returned.  On error, -1 is returned, and errno is set appropri-
       ately.

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 ALSO
       fork(2), read(2), socketpair(2), write(2), popen(3), pipe(7)



Linux 2.6.7                       2004-06-17                           PIPE(2)

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