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28 .\" @(#)pipe.2 8.1 (Berkeley) 6/4/93
29 .\" $FreeBSD: src/lib/libc/sys/pipe.2,v 1.13.2.5 2001/12/14 18:34:01 ru Exp $
30 .\" $DragonFly: src/lib/libc/sys/pipe.2,v 1.2 2003/06/17 04:26:47 dillon Exp $
38 .Nd create descriptor pair for interprocess communication
44 .Fn pipe "int *fildes"
46 .Fn pipe2 "int fildes[2]" "int flags"
53 which is an object allowing
54 bidirectional data flow,
55 and allocates a pair of file descriptors.
59 system call allows control over the attributes of the file descriptors
65 are constructed by a bitwise-inclusive OR of flags from the following
68 .Bl -tag -width ".Dv O_NONBLOCK"
70 Set the close-on-exec flag for the new file descriptors.
72 Set the non-blocking flag for the ends of the pipe.
77 argument is 0, the behavior is identical to a call to
80 By convention, the first descriptor is normally used as the
83 and the second is normally the
85 so that data written to
87 appears on (i.e., can be read from)
89 This allows the output of one program to be
92 the source's standard output is set up to be
93 the write end of the pipe,
94 and the sink's standard input is set up to be
95 the read end of the pipe.
96 The pipe itself persists until all its associated descriptors are
99 A pipe that has had an end closed is considered
101 Writing on such a pipe causes the writing process to receive
105 Widowing a pipe is the only way to deliver end-of-file to a reader:
106 after the reader consumes any buffered data, reading a widowed pipe
107 returns a zero count.
109 The bidirectional nature of this implementation of pipes is not
110 portable to older systems, so it is recommended to use the convention
111 for using the endpoints in the traditional manner when using a
112 pipe in one direction.
120 system calls will fail if:
123 Too many descriptors are active.
125 The system file table is full.
129 buffer is in an invalid area of the process's address
135 system call will also fail if:
151 function call appeared in
154 Bidirectional pipes were first used on