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PIPE(2)			  FreeBSD 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()	system call creates a pipe, which is an	object allowing	bidi-
     rectional data flow, and allocates	a pair of file descriptors.

     The pipe2() system	call allows control over the attributes	of the file
     descriptors via the flags argument.  Values for flags are constructed by
     a bitwise-inclusive OR of flags from the following	list, defined in
     <fcntl.h>:

     O_CLOEXEC	 Set the close-on-exec flag for	the new	file descriptors.

     O_NONBLOCK	 Set the non-blocking flag for the ends	of the pipe.

     If	the flags argument is 0, the behavior is identical to a	call to
     pipe().

     By	convention, the	first descriptor is normally used as the read end of
     the pipe, and the second is normally 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 that has had an end	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 bidirectional nature of this implementation of	pipes is not portable
     to	older systems, so it is	recommended to use the convention for using
     the endpoints in the traditional manner when using	a pipe in one direc-
     tion.

RETURN VALUES
     The pipe()	function returns the value 0 if	successful; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

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

     [EMFILE]		Too many descriptors are active.

     [ENFILE]		The system file	table is full.

     [ENOMEM]		Not enough kernel memory to establish a	pipe.

     The pipe2() system	call will also fail if:

     [EINVAL]		The flags argument is invalid.

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

HISTORY
     The pipe()	function appeared in Version 3 AT&T UNIX.

     Bidirectional pipes were first used on AT&T System	V Release 4 UNIX.

     The pipe2() function appeared in FreeBSD 10.0.

FreeBSD	10.1			  May 1, 2013			  FreeBSD 10.1

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

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