ultrix man page for pipe

pipe(2) 							System Calls Manual							   pipe(2)

Name
       pipe - create an interprocess channel

Syntax
       include <limits.h> /*Definition of PIPE_MAX*/
       pipe(fildes)
       int fildes[2];

Arguments
       fildes	 Passing an address as an array of two integers into the system call.

Description
       The system call creates an I/O mechanism called a pipe.	The file descriptors returned can be used in and operations.  Their integer values
       will be the two lowest available at the time of the function call.  The O_NONBLOCK and FD_CLOEXEC flags will be clear on both file descrip-
       tors.

       When the pipe is written using the descriptor fildes[1], up to PIPE_MAX bytes of data are buffered before the writing process is suspended.
       A read using the descriptor fildes[0] picks up the data.

       It is assumed that after the pipe has been set up, two (or more) cooperating processes (created by subsequent calls) pass data through  the
       pipe with and calls.

       The shell has a syntax to set up a linear array of processes connected by pipes.

       For further information on how and calls behave with pipes, see the and reference pages.

       A signal is generated if a write on a pipe with only one end is attempted.

Restrictions
       Should more than 4096 bytes be necessary in any pipe among a loop of processes, deadlock may occur.

       The  underlying	implementation	of  pipes is no longer socket based, but rather implemented through the file system.  Any application that
       needs socket functionality from pipes should use the system call.

Return Values
       The function value zero is returned if the pipe was created; -1 if an error occurred.

Diagnostics
       The call fails if:

       [EMFILE]       Too many descriptors are active.

       [ENFILE]       The system file table is full.

       [EFAULT]       The fildes buffer is in an invalid area of the process's address space.

Environment
       Differs from the System V definition in that ENFILE is not a possible error condition.

See Also
       sh(1), fork(2), read(2), socketpair(2), write(2)

																	   pipe(2)