1 .\" Copyright (c) 1980, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
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. Neither the name of the University nor the names of its contributors
13 .\" may be used to endorse or promote products derived from this software
14 .\" without specific prior written permission.
16 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" @(#)pipe.2 8.1 (Berkeley) 6/4/93
37 .Nd create descriptor pair for interprocess communication
43 .Fn pipe "int fildes[2]"
45 .Fn pipe2 "int fildes[2]" "int flags"
52 which is an object allowing
53 bidirectional data flow,
54 and allocates a pair of file descriptors.
58 system call allows control over the attributes of the file descriptors
64 are constructed by a bitwise-inclusive OR of flags from the following
67 .Bl -tag -width ".Dv O_NONBLOCK"
69 Set the close-on-exec flag for the new file descriptors.
71 Set the non-blocking flag for the ends of the pipe.
76 argument is 0, the behavior is identical to a call to
79 By convention, the first descriptor is normally used as the
82 and the second is normally the
84 so that data written to
86 appears on (i.e., can be read from)
88 This allows the output of one program to be
91 the source's standard output is set up to be
92 the write end of the pipe,
93 and the sink's standard input is set up to be
94 the read end of the pipe.
95 The pipe itself persists until all its associated descriptors are
98 A pipe that has had an end closed is considered
100 Writing on such a pipe causes the writing process to receive
104 Widowing a pipe is the only way to deliver end-of-file to a reader:
105 after the reader consumes any buffered data, reading a widowed pipe
106 returns a zero count.
108 The bidirectional nature of this implementation of pipes is not
109 portable to older systems, so it is recommended to use the convention
110 for using the endpoints in the traditional manner when using a
111 pipe in one direction.
112 .Sh IMPLEMENTATION NOTES
118 As a result, system call traces such as those captured by
131 system calls will fail if:
135 argument points to an invalid memory location.
137 Too many descriptors are active.
139 The system file table is full.
141 Not enough kernel memory to establish a pipe.
146 system call will also fail if:
165 Bidirectional pipes were first used on
175 function became a wrapper around