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1 | .\" Copyright (c) 1980, 1991 Regents of the University of California. |
2 | .\" All rights reserved. | |
c15b236d | 3 | .\" |
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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. | |
c15b236d | 19 | .\" |
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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. | |
931b8415 | 31 | .\" |
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32 | .\" @(#)pipe.2 6.3 (Berkeley) 3/10/91 |
33 | .\" | |
34 | .Dd March 10, 1991 | |
931b8415 CL |
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 | |
c15b236d | 45 | The |
931b8415 CL |
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 | |
0bbf2c7d | 82 | Pipes are really a special case of the |
931b8415 | 83 | .Xr socketpair 2 |
0bbf2c7d | 84 | call and, in fact, are implemented as such in the system. |
931b8415 CL |
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 | |
0bbf2c7d | 97 | Too many descriptors are active. |
931b8415 | 98 | .It Bq Er ENFILE |
fd690c8b | 99 | The system file table is full. |
931b8415 CL |
100 | .It Bq Er EFAULT |
101 | The | |
102 | .Fa fildes | |
103 | buffer is in an invalid area of the process's address | |
0bbf2c7d | 104 | space. |
931b8415 CL |
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. |