term% cat index.txt PIPE(2) System Calls Manual 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 us‐
ing the descriptor fildes[0] will pick up the data. Writes with a
count of 4096 bytes or less are atomic; no other process can inter‐
sperse data.
It is assumed that after the pipe has been set up, two (or more) coop‐
erating 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
(pipe = 42.)
sys pipe
(read file descriptor in r0)
(write file descriptor in r1)
PIPE(2)