[unix-history] / usr / man / man2 / pipe.2

.TH PIPE 2 
.SH NAME
pipe \- create an interprocess channel
.SH SYNOPSIS
.B pipe(fildes)
.br
.B int fildes[2];
.SH DESCRIPTION
The
.I 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
.IR fildes [1]
up to 4096 bytes of data are buffered
before the writing process is suspended.
A read using the descriptor
.IR fildes [0]
will pick up the data.
.PP
It is assumed that after the
pipe has been set up,
two (or more)
cooperating processes
(created by subsequent
.I fork
calls)
will pass data through the
pipe with
.I read
and
.I write
calls.
.PP
The Shell has a syntax
to set up a linear array of processes
connected by pipes.
.PP
Read calls on an empty
pipe (no buffered data) with only one end
(all write file descriptors closed)
returns an end-of-file.
.SH "SEE ALSO"
sh(1), read(2), write(2), fork(2)
.SH 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.
.SH BUGS
Should more than 4096 bytes be necessary in any
pipe among a loop of processes, deadlock will occur.
.SH "ASSEMBLER (PDP-11)"
(pipe = 42.)
.br
.B sys pipe
.br
(read file descriptor in r0)
.br
(write file descriptor in r1)
Commit	Line	Data
e6817382 BJ	1	.TH PIPE 2
	2	.SH NAME
	3	pipe \- create an interprocess channel
	4	.SH SYNOPSIS
	5	.B pipe(fildes)
	6	.br
	7	.B int fildes[2];
	8	.SH DESCRIPTION
	9	The
	10	.I pipe
	11	system call
	12	creates an I/O mechanism called a pipe.
	13	The file descriptors returned can
	14	be used in read and write operations.
	15	When the pipe is written using the descriptor
	16	.IR fildes [1]
	17	up to 4096 bytes of data are buffered
	18	before the writing process is suspended.
	19	A read using the descriptor
	20	.IR fildes [0]
	21	will pick up the data.
	22	.PP
	23	It is assumed that after the
	24	pipe has been set up,
	25	two (or more)
	26	cooperating processes
	27	(created by subsequent
	28	.I fork
	29	calls)
	30	will pass data through the
	31	pipe with
	32	.I read
	33	and
	34	.I write
	35	calls.
	36	.PP
	37	The Shell has a syntax
	38	to set up a linear array of processes
	39	connected by pipes.
	40	.PP
	41	Read calls on an empty
	42	pipe (no buffered data) with only one end
	43	(all write file descriptors closed)
	44	returns an end-of-file.
	45	.SH "SEE ALSO"
	46	sh(1), read(2), write(2), fork(2)
	47	.SH DIAGNOSTICS
	48	The function value zero is returned if the
	49	pipe was created; \-1 if
	50	too many files are already open.
	51	A signal is generated if a write on a pipe with only one end is attempted.
	52	.SH BUGS
	53	Should more than 4096 bytes be necessary in any
	54	pipe among a loop of processes, deadlock will occur.
	55	.SH "ASSEMBLER (PDP-11)"
	56	(pipe = 42.)
	57	.br
	58	.B sys pipe
	59	.br
	60	(read file descriptor in r0)
	61	.br
	62	(write file descriptor in r1)