.ref-BSD-4_3_Net_2/usr/src/lib/libc/sys/pipe.2

.\" Copyright (c) 1980, 1991 Regents of the University of California.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)pipe.2	6.3 (Berkeley) 3/10/91
.\"
.Dd March 10, 1991
.Dt PIPE 2
.Os BSD 4
.Sh NAME
.Nm pipe
.Nd create descriptor pair for interprocess communication
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fn pipe "int *fildes"
.Sh DESCRIPTION
The
.Fn pipe
function
creates a
.Em pipe ,
which is an object allowing
unidirectional data flow,
and allocates a pair of file descriptors.
The first descriptor connects to the
.Em read end
of the pipe,
and the second connects to the
.Em write end  ,
so that data written to
.Fa fildes[1]
appears on (i.e., can be read from)
.Fa fildes[0] .
This allows the output of one program to be
sent
to another program:
the source's standard output is set up to be
the write end of the pipe,
and the sink's standard input is set up to be
the read end of the pipe.
The pipe itself persists until all its associated descriptors are
closed.
.Pp
A pipe whose read or write end has been closed is considered
.Em widowed .
Writing on such a pipe causes the writing process to receive
a
.Dv SIGPIPE
signal.
Widowing a pipe is the only way to deliver end-of-file to a reader:
after the reader consumes any buffered data, reading a widowed pipe
returns a zero count.
.Pp
Pipes are really a special case of the
.Xr socketpair 2
call and, in fact, are implemented as such in the system.
.Sh RETURN VALUES
On successful creation of the pipe, zero is returned. Otherwise,
a value of -1 is returned and the variable
.Va errno
set to indicate the
error.
.Sh ERRORS
The
.Fn pipe
call will fail if:
.Bl -tag -width [EMFILE]
.It Bq Er EMFILE
Too many descriptors are active.
.It Bq Er ENFILE
The system file table is full.
.It Bq Er EFAULT
The
.Fa fildes
buffer is in an invalid area of the process's address
space.
.El
.Sh SEE ALSO
.Xr sh 1 ,
.Xr read 2 ,
.Xr write 2 ,
.Xr fork 2 ,
.Xr socketpair 2
.Sh HISTORY
A
.Nm
function call appeared in Version 6 AT&T UNIX.
Commit	Line	Data
	1	.\" Copyright (c) 1980, 1991 Regents of the University of California.
	2	.\" All rights reserved.
	3	.\"
	4	.\" Redistribution and use in source and binary forms, with or without
	5	.\" modification, are permitted provided that the following conditions
	6	.\" are met:
	7	.\" 1. Redistributions of source code must retain the above copyright
	8	.\" notice, this list of conditions and the following disclaimer.
	9	.\" 2. Redistributions in binary form must reproduce the above copyright
	10	.\" notice, this list of conditions and the following disclaimer in the
	11	.\" documentation and/or other materials provided with the distribution.
	12	.\" 3. All advertising materials mentioning features or use of this software
	13	.\" must display the following acknowledgement:
	14	.\" This product includes software developed by the University of
	15	.\" California, Berkeley and its contributors.
	16	.\" 4. Neither the name of the University nor the names of its contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" @(#)pipe.2 6.3 (Berkeley) 3/10/91
	33	.\"
	34	.Dd March 10, 1991
	35	.Dt PIPE 2
	36	.Os BSD 4
	37	.Sh NAME
	38	.Nm pipe
	39	.Nd create descriptor pair for interprocess communication
	40	.Sh SYNOPSIS
	41	.Fd #include <unistd.h>
	42	.Ft int
	43	.Fn pipe "int *fildes"
	44	.Sh DESCRIPTION
	45	The
	46	.Fn pipe
	47	function
	48	creates a
	49	.Em pipe ,
	50	which is an object allowing
	51	unidirectional data flow,
	52	and allocates a pair of file descriptors.
	53	The first descriptor connects to the
	54	.Em read end
	55	of the pipe,
	56	and the second connects to the
	57	.Em write end ,
	58	so that data written to
	59	.Fa fildes[1]
	60	appears on (i.e., can be read from)
	61	.Fa fildes[0] .
	62	This allows the output of one program to be
	63	sent
	64	to another program:
	65	the source's standard output is set up to be
	66	the write end of the pipe,
	67	and the sink's standard input is set up to be
	68	the read end of the pipe.
	69	The pipe itself persists until all its associated descriptors are
	70	closed.
	71	.Pp
	72	A pipe whose read or write end has been closed is considered
	73	.Em widowed .
	74	Writing on such a pipe causes the writing process to receive
	75	a
	76	.Dv SIGPIPE
	77	signal.
	78	Widowing a pipe is the only way to deliver end-of-file to a reader:
	79	after the reader consumes any buffered data, reading a widowed pipe
	80	returns a zero count.
	81	.Pp
	82	Pipes are really a special case of the
	83	.Xr socketpair 2
	84	call and, in fact, are implemented as such in the system.
	85	.Sh RETURN VALUES
	86	On successful creation of the pipe, zero is returned. Otherwise,
	87	a value of -1 is returned and the variable
	88	.Va errno
	89	set to indicate the
	90	error.
	91	.Sh ERRORS
	92	The
	93	.Fn pipe
	94	call will fail if:
	95	.Bl -tag -width [EMFILE]
	96	.It Bq Er EMFILE
	97	Too many descriptors are active.
	98	.It Bq Er ENFILE
	99	The system file table is full.
	100	.It Bq Er EFAULT
	101	The
	102	.Fa fildes
	103	buffer is in an invalid area of the process's address
	104	space.
	105	.El
	106	.Sh SEE ALSO
	107	.Xr sh 1 ,
	108	.Xr read 2 ,
	109	.Xr write 2 ,
	110	.Xr fork 2 ,
	111	.Xr socketpair 2
	112	.Sh HISTORY
	113	A
	114	.Nm
	115	function call appeared in Version 6 AT&T UNIX.