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NetBSD 6.1.5 - man page for pipe (netbsd section 2)

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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 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[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
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