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PIPE(2)			    BSD	System Calls Manual		       PIPE(2)

NAME
     pipe -- create descriptor pair for	interprocess communication

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     pipe(int fildes[2]);

     int
     pipe2(int fildes[2], int flags);

DESCRIPTION
     The pipe()	function creates a pipe, which is an object allowing unidirec-
     tional 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[1] appears on (i.e., can
     be	read from) fildes[0].  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.

     The pipe2() function behaves exactly like pipe() only it allows extra
     flags to be set on	the returned file descriptor.  The following flags are
     valid:

	   O_CLOEXEC   Set the "close-on-exec" property.

	   O_NONBLOCK  Sets non-blocking I/O.

	   O_NOSIGPIPE
		       Return EPIPE instead of raising SIGPIPE.

RETURN VALUES
     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.

ERRORS
     The pipe()	and pipe2() calls will fail if:

     [EFAULT]		The fildes buffer is in	an invalid area	of the
			process's address space.  The reliable detection of
			this error cannot be guaranteed; when not detected, a
			signal may be delivered	to the process,	indicating an
			address	violation.

     [EMFILE]		Too many descriptors are active.

     [ENFILE]		The system file	table is full.

     pipe2() will also fail if:

     [EINVAL]		flags is other than O_NONBLOCK or O_CLOEXEC.

SEE ALSO
     sh(1), fork(2), read(2), socketpair(2), write(2)

STANDARDS
     The pipe()	function conforms to ISO/IEC 9945-1:1990 ("POSIX.1").

HISTORY
     A pipe() function call appeared in	Version	6 AT&T UNIX.  The pipe2()
     function is inspired from Linux and appeared in NetBSD 6.0.

BSD			       January 23, 2012				   BSD

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY

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