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

.TH PIPE 2 "12 February 1983"
.UC 4
.SH NAME
pipe \- create an interprocess communication channel
.SH SYNOPSIS
.nf
.ft B
pipe(fildes)
int fildes[2];
.fi
.ft R
.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.
.PP
Pipes are really a special case of the 
.IR socketpair (2)
call and, in fact, are implemented as such in the system.
.PP
A signal is generated if a write on a pipe with only one end is attempted.
.SH "RETURN VALUE
The function value zero is returned if the
pipe was created; \-1 if an error occurred.
.SH ERRORS
The \fIpipe\fP call will fail if:
.TP 15
[EMFILE]
Too many descriptors are active.
.TP 15
[EFAULT]
The \fIfildes\fP buffer is in an invalid area of the process's address
space.
.SH "SEE ALSO"
sh(1), read(2), write(2), fork(2), socketpair(2)
.SH BUGS
Should more than 4096 bytes be necessary in any
pipe among a loop of processes, deadlock will occur.
Commit	Line	Data
ea709105 C	1	.TH PIPE 2 "12 February 1983"
	2	.UC 4
	3	.SH NAME
	4	pipe \- create an interprocess communication channel
	5	.SH SYNOPSIS
	6	.nf
	7	.ft B
	8	pipe(fildes)
	9	int fildes[2];
	10	.fi
	11	.ft R
	12	.SH DESCRIPTION
	13	The
	14	.I pipe
	15	system call
	16	creates an I/O mechanism called a pipe.
	17	The file descriptors returned can
	18	be used in read and write operations.
	19	When the pipe is written using the descriptor
	20	.IR fildes [1]
	21	up to 4096 bytes of data are buffered
	22	before the writing process is suspended.
	23	A read using the descriptor
	24	.IR fildes [0]
	25	will pick up the data.
	26	.PP
	27	It is assumed that after the
	28	pipe has been set up,
	29	two (or more)
	30	cooperating processes
	31	(created by subsequent
	32	.I fork
	33	calls)
	34	will pass data through the
	35	pipe with
	36	.I read
	37	and
	38	.I write
	39	calls.
	40	.PP
	41	The shell has a syntax
	42	to set up a linear array of processes
	43	connected by pipes.
	44	.PP
	45	Read calls on an empty
	46	pipe (no buffered data) with only one end
	47	(all write file descriptors closed)
	48	returns an end-of-file.
	49	.PP
	50	Pipes are really a special case of the
	51	.IR socketpair (2)
	52	call and, in fact, are implemented as such in the system.
	53	.PP
	54	A signal is generated if a write on a pipe with only one end is attempted.
	55	.SH "RETURN VALUE
	56	The function value zero is returned if the
	57	pipe was created; \-1 if an error occurred.
	58	.SH ERRORS
	59	The \fIpipe\fP call will fail if:
	60	.TP 15
	61	[EMFILE]
	62	Too many descriptors are active.
	63	.TP 15
	64	[EFAULT]
65	The \fIfildes\fP buffer is in an invalid area of the process's address
66	space.
67	.SH "SEE ALSO"
68	sh(1), read(2), write(2), fork(2), socketpair(2)
69	.SH BUGS
70	Should more than 4096 bytes be necessary in any
71	pipe among a loop of processes, deadlock will occur.