pipe program in C Post: 302473549

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LEARN ABOUT NETBSD

pipe

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