1.\" Copyright (c) 1980, 1991, 1993
2.\" The Regents of the University of California. 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 8.1 (Berkeley) 6/4/93
| 1.\" Copyright (c) 1980, 1991, 1993
2.\" The Regents of the University of California. 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 8.1 (Berkeley) 6/4/93
|
33.\" $FreeBSD: head/lib/libc/sys/pipe.2 50476 1999-08-28 00:22:10Z peter $
| 33.\" $FreeBSD: head/lib/libc/sys/pipe.2 57686 2000-03-02 09:14:21Z sheldonh $
|
34.\"
35.Dd June 4, 1993
36.Dt PIPE 2
37.Os BSD 4
38.Sh NAME
39.Nm pipe
40.Nd create descriptor pair for interprocess communication
41.Sh SYNOPSIS
42.Fd #include <unistd.h>
43.Ft int
44.Fn pipe "int *fildes"
45.Sh DESCRIPTION
46The
47.Fn pipe
48function
49creates a
50.Em pipe ,
51which is an object allowing
52bidirectional data flow,
53and allocates a pair of file descriptors.
54.Pp
55By convention, the first descriptor is normally used as the
56.Em read end
57of the pipe,
58and the second is normally the
59.Em write end ,
60so that data written to
61.Fa fildes[1]
62appears on (i.e., can be read from)
63.Fa fildes[0] .
64This allows the output of one program to be
65sent
66to another program:
67the source's standard output is set up to be
68the write end of the pipe,
69and the sink's standard input is set up to be
70the read end of the pipe.
71The pipe itself persists until all its associated descriptors are
72closed.
73.Pp
74A pipe that has had an end closed is considered
75.Em widowed .
76Writing on such a pipe causes the writing process to receive
77a
78.Dv SIGPIPE
79signal.
80Widowing a pipe is the only way to deliver end-of-file to a reader:
81after the reader consumes any buffered data, reading a widowed pipe
82returns a zero count.
83.Pp
84The bidirectional nature of this implementation of pipes is not
85portable to older systems, so it is recommended to use the convention
86for using the endpoints in the traditional manner when using a
87pipe in one direction.
88.Sh RETURN VALUES
| 34.\"
35.Dd June 4, 1993
36.Dt PIPE 2
37.Os BSD 4
38.Sh NAME
39.Nm pipe
40.Nd create descriptor pair for interprocess communication
41.Sh SYNOPSIS
42.Fd #include <unistd.h>
43.Ft int
44.Fn pipe "int *fildes"
45.Sh DESCRIPTION
46The
47.Fn pipe
48function
49creates a
50.Em pipe ,
51which is an object allowing
52bidirectional data flow,
53and allocates a pair of file descriptors.
54.Pp
55By convention, the first descriptor is normally used as the
56.Em read end
57of the pipe,
58and the second is normally the
59.Em write end ,
60so that data written to
61.Fa fildes[1]
62appears on (i.e., can be read from)
63.Fa fildes[0] .
64This allows the output of one program to be
65sent
66to another program:
67the source's standard output is set up to be
68the write end of the pipe,
69and the sink's standard input is set up to be
70the read end of the pipe.
71The pipe itself persists until all its associated descriptors are
72closed.
73.Pp
74A pipe that has had an end closed is considered
75.Em widowed .
76Writing on such a pipe causes the writing process to receive
77a
78.Dv SIGPIPE
79signal.
80Widowing a pipe is the only way to deliver end-of-file to a reader:
81after the reader consumes any buffered data, reading a widowed pipe
82returns a zero count.
83.Pp
84The bidirectional nature of this implementation of pipes is not
85portable to older systems, so it is recommended to use the convention
86for using the endpoints in the traditional manner when using a
87pipe in one direction.
88.Sh RETURN VALUES
|
89On successful creation of the pipe, zero is returned. Otherwise,
| 89On successful creation of the pipe, zero is returned.
90Otherwise,
|
90a value of -1 is returned and the variable
91.Va errno
92set to indicate the
93error.
94.Sh ERRORS
95The
96.Fn pipe
97call will fail if:
98.Bl -tag -width [EMFILE]
99.It Bq Er EMFILE
100Too many descriptors are active.
101.It Bq Er ENFILE
102The system file table is full.
103.It Bq Er EFAULT
104The
105.Fa fildes
106buffer is in an invalid area of the process's address
107space.
108.El
109.Sh SEE ALSO
110.Xr sh 1 ,
111.Xr fork 2 ,
112.Xr read 2 ,
113.Xr socketpair 2 ,
114.Xr write 2
115.Sh HISTORY
116A
117.Fn pipe
118function call appeared in
119.At v3 .
120.Pp
121Bidirectional pipes were first used on
122.At V.4 .
| 91a value of -1 is returned and the variable
92.Va errno
93set to indicate the
94error.
95.Sh ERRORS
96The
97.Fn pipe
98call will fail if:
99.Bl -tag -width [EMFILE]
100.It Bq Er EMFILE
101Too many descriptors are active.
102.It Bq Er ENFILE
103The system file table is full.
104.It Bq Er EFAULT
105The
106.Fa fildes
107buffer is in an invalid area of the process's address
108space.
109.El
110.Sh SEE ALSO
111.Xr sh 1 ,
112.Xr fork 2 ,
113.Xr read 2 ,
114.Xr socketpair 2 ,
115.Xr write 2
116.Sh HISTORY
117A
118.Fn pipe
119function call appeared in
120.At v3 .
121.Pp
122Bidirectional pipes were first used on
123.At V.4 .
|