PIPE(2)

NAME
pipe - create an interprocess channel

SYNOPSIS
pipe(fildes)
int fildes[2];

DESCRIPTION
The pipe system call creates an I/O mechanism called a pipe. The file descriptors returned can be used in read and write operations. When the pipe is written using the descriptor fildes[1] up to 4096 bytes of data are buffered before the writing process is suspended. A read using the descriptor fildes[0] will pick up the data.

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

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

Read calls on an empty pipe (no buffered data) with only one end (all write file descriptors closed) returns an end-of-file.

SEE ALSO
sh(1), read(2), write(2), fork(2)

DIAGNOSTICS
The function value zero is returned if the pipe was created; -1 if too many files are already open. A signal is generated if a write on a pipe with only one end is attempted.

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

ASSEMBLER (PDP-11)
(pipe = 42.)
sys pipe
(read file descriptor in r0)
(write file descriptor in r1)