pipe

Syntax

#include <unistd.h> int pipe(int fildes[2]);

Description

This function creates a pipe and places a file descriptor for the read end of the pipe in fildes[0], and another for the write end in fildes[1]. Data written to fildes[1] will be read from fildes[0] on a first-in first-out (FIFO) basis.

Note this pipe implementation won't help port instances of fork/exec or any other methods that require support for multitasking.

Return Value

Zero for success, otherwise -1 is returned and errno is set to indicate the error.

Portability

ANSI/ISO C	No
POSIX	1003.2-1992; 1003.1-2001

Example

#include <unistd.h> #include <process.h> /* Pipe the output of program to the input of another. */ int main() { int pipe_fds[2]; int stdin_save, stdout_save; if (pipe(pipe_fds) < 0) return -1; /* Duplicate stdin and stdout so we can restore them later. */ stdin_save = dup(STDIN_FILENO); stdout_save = dup(STDOUT_FILENO); /* Make the write end of the pipe stdout. */ dup2(pipe_fds[1], STDOUT_FILENO); /* Run the program. Its output will be written to the pipe. */ spawnl(P_WAIT, "/dev/env/DJDIR/bin/ls.exe", "ls.exe", NULL); /* Close the write end of the pipe. */ close(pipe_fds[1]); /* Restore stdout. */ dup2(stdout_save, STDOUT_FILENO); /* Make the read end of the pipe stdin. */ dup2(pipe_fds[0], STDIN_FILENO); /* Run another program. Its input will come from the output of the first program. */ spawnl(P_WAIT, "/dev/env/DJDIR/bin/less.exe", "less.exe", "-E", NULL); /* Close the read end of the pipe. */ close(pipe_fds[0]); /* Restore stdin. */ dup2(stdin_save, STDIN_FILENO); return 0; }