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PIPE(2)			  FreeBSD System Calls Manual		       PIPE(2)

NAME
     pipe, pipe2 -- create descriptor pair for interprocess communication

SYNOPSIS
     #include <unistd.h>

     int
     pipe(int fildes[2]);

     #include <fcntl.h>
     #include <unistd.h>

     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 is identical to pipe() except	that the non-blocking
     I/O mode on both ends of the pipe is determined by	the O_NONBLOCK flag in
     the flags argument	and the	close-on-exec flag on both the new file	de-
     scriptors is determined by	the O_CLOEXEC flag in the flags	argument.

RETURN VALUES
     Upon successful completion, the value 0 is	returned; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     pipe() and	pipe2()	will succeed unless:

     [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.

     In	addition, pipe2() may return the following error:

     [EINVAL]		flags is invalid.

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

STANDARDS
     The pipe()	function conforms to IEEE Std 1003.1-2008 ("POSIX.1").	The
     pipe2() function is expected to conform to	a future revision of that
     standard.

     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 portabil-
     ity.

HISTORY
     A pipe() function call appeared in	Version	3 AT&T UNIX.  Since Version 4
     AT&T UNIX,	it allocates two distinct file descriptors.  The pipe2() func-
     tion appeared in OpenBSD 5.7.

FreeBSD	13.0		       December	10, 2014		  FreeBSD 13.0

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

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