PIPE(2) OpenBSD Programmer's Manual PIPE(2)
pipe - create descriptor pair for interprocess communication
The pipe() function creates a pipe, which is an object allowing
unidirectional data flow, and allocates a pair of file descriptors. The
first descriptor connects to the read end of the pipe, and the second
connects to the write end, so that data written to fildes appears on
(i.e., can be read from) fildes. 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.
A pipe whose read or write end has been closed is considered widowed.
Writing on such a pipe causes the writing process to receive a 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.
On successful creation of the pipe, zero is returned. Otherwise, a value
of -1 is returned and the variable errno set to indicate the error.
The pipe() call will fail if:
[EMFILE] Too many descriptors are active.
[ENFILE] The system file table is full.
[EFAULT] The fildes buffer is in an invalid area of the
process's address space.
sh(1), fork(2), read(2), socketpair(2), write(2)
The pipe() function conforms to IEEE Std 1003.1-2008 (``POSIX.1'').
As an extension, the pipe provided is actually capable of moving data
bidirectionally. This is compatible with SVR4. However, this is non-
POSIX behaviour which should not be relied on, for reasons of
A pipe() function call appeared in Version 3 AT&T UNIX. Since Version 4
AT&T UNIX, it allocates two distict file descriptors.
OpenBSD 5.4 July 17, 2013 OpenBSD 5.4
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