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

.th PIPE II 8/5/73
.sh NAME
pipe \*- create a pipe
.sh SYNOPSIS
(pipe = 42.)
.br
.ft B
sys pipe
.br
.ft R
(read file descriptor in r0)
.br
(write file descriptor in r1)
.s3
.ft B
pipe(fildes)
.br
int fildes[2];
.ft R
.sh DESCRIPTION
The
.it 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
returned in r1 (resp. fildes[1]),
up to 4096 bytes of data are buffered
before the writing process is suspended.
A read using the descriptor returned in r0
(resp. fildes[0])
will pick up the data.
.s3
It is assumed that after the
pipe has been set up,
two (or more)
cooperating processes
(created by subsequent
.it fork
calls)
will pass data through the
pipe with
.it read
and
.it write
calls.
.s3
The shell has a syntax
to set up a linear array of processes
connected by pipes.
.s3
Read calls on an empty
pipe (no buffered data) with only one end
(all write file descriptors closed)
return an end-of-file.
Write calls under similar conditions are ignored.
.sh "SEE ALSO"
sh(I), read(II), write(II), fork(II)
.sh DIAGNOSTICS
The error
bit (c-bit) is set if
more than
8 files are already open.
From C, a \*-1 returned value
indicates an error.
Commit	Line	Data
88d0a458 KT	1	.th PIPE II 8/5/73
	2	.sh NAME
	3	pipe \*- create a pipe
	4	.sh SYNOPSIS
	5	(pipe = 42.)
	6	.br
	7	.ft B
	8	sys pipe
	9	.br
	10	.ft R
	11	(read file descriptor in r0)
	12	.br
	13	(write file descriptor in r1)
	14	.s3
	15	.ft B
	16	pipe(fildes)
	17	.br
	18	int fildes[2];
	19	.ft R
	20	.sh DESCRIPTION
	21	The
	22	.it pipe
	23	system call
	24	creates an I/O mechanism called a pipe.
	25	The file descriptors returned can
	26	be used in read and write operations.
	27	When the pipe is written using the descriptor
	28	returned in r1 (resp. fildes[1]),
	29	up to 4096 bytes of data are buffered
	30	before the writing process is suspended.
	31	A read using the descriptor returned in r0
	32	(resp. fildes[0])
	33	will pick up the data.
	34	.s3
	35	It is assumed that after the
	36	pipe has been set up,
	37	two (or more)
	38	cooperating processes
	39	(created by subsequent
	40	.it fork
	41	calls)
	42	will pass data through the
	43	pipe with
	44	.it read
	45	and
	46	.it write
	47	calls.
	48	.s3
	49	The shell has a syntax
	50	to set up a linear array of processes
	51	connected by pipes.
	52	.s3
	53	Read calls on an empty
	54	pipe (no buffered data) with only one end
	55	(all write file descriptors closed)
	56	return an end-of-file.
	57	Write calls under similar conditions are ignored.
	58	.sh "SEE ALSO"
	59	sh(I), read(II), write(II), fork(II)
	60	.sh DIAGNOSTICS
	61	The error
	62	bit (c-bit) is set if
	63	more than
	64	8 files are already open.
65	From C, a \*-1 returned value
66	indicates an error.