pipe Subroutine

Purpose

Creates an interprocess channel.

Library

Standard C Library (libc.a)

Syntax

#include <unistd.h>

int pipe ( FileDescriptor)
int FileDescriptor[2];

Description

The pipe subroutine creates an interprocess channel that is called a pipe and returns two file descriptors, FileDescriptor[0] and FileDescriptor[1]. FileDescriptor[0] is opened for reading and FileDescriptor[1] is opened for writing.

A read operation on the FileDescriptor[0] parameter accesses the data that is written to the FileDescriptor[1] parameter on a first-in, first-out (FIFO) basis.

Write requests of PIPE_BUF bytes or fewer will not be interleaved (mixed) with data from other processes doing writes on the same pipe. PIPE_BUF is a system variable that is described in the pathconf subroutine. Writes of greater than PIPE_BUF bytes may have data that is interleaved, on arbitrary boundaries, with other writes.

If O_NONBLOCK or O_NDELAY are set, writes requests of PIPE_BUF bytes or fewer will either succeed completely or fail and return -1 with the errno global variable set to EAGAIN. A write request for more than PIPE_BUF bytes will either transfer what it can and return the number of bytes actually written, or transfer no data and return -1 with the errno global variable set to EAGAIN.

Parameters

Return Values

Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned, and the errno global variable is set to identify the error.

Error Codes

The pipe subroutine is unsuccessful if one or more the following are true: