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PIPE(3P)                   POSIX Programmer's Manual                  PIPE(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       pipe - create an interprocess channel
SYNOPSIS
       #include <unistd.h>
       int pipe(int fildes[2]);

DESCRIPTION
       The pipe() function shall create a pipe and place two file descriptors,
       one  each into the arguments fildes[0] and fildes[1], that refer to the
       open file descriptions for the read and write ends of the  pipe.  Their
       integer  values  shall  be  the two lowest available at the time of the
       pipe() call. The O_NONBLOCK and FD_CLOEXEC flags shall be clear on both
       file  descriptors.  (The fcntl() function can be used to set both these
       flags.)
       Data can be written to the file descriptor fildes[1] and read from  the
       file  descriptor  fildes[0].  A  read  on the file descriptor fildes[0]
       shall access data written to the file descriptor fildes[1] on a  first-
       in-first-out  basis.   It is unspecified whether fildes[0] is also open
       for writing and whether fildes[1] is also open for reading.
       A process has the pipe open for reading (correspondingly writing) if it
       has  a  file  descriptor  open  that  refers to the read end, fildes[0]
       (write end, fildes[1]).
       Upon successful completion, pipe() shall mark for update the  st_atime,
       st_ctime, and st_mtime fields of the pipe.
RETURN VALUE
       Upon successful completion, 0 shall be returned; otherwise, -1 shall be
       returned and errno set to indicate the error.
ERRORS
       The pipe() function shall fail if:
       EMFILE More than {OPEN_MAX} minus two file descriptors are  already  in
              use by this process.
       ENFILE The  number  of  simultaneously  open  files in the system would
              exceed a system-imposed limit.

       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       None.
RATIONALE
       The wording carefully avoids using the verb "to open" in order to avoid
       any implication of use of open(); see also write() .
FUTURE DIRECTIONS
       None.
SEE ALSO
       fcntl(),    read(),   write(),   the   Base   Definitions   volume   of
       IEEE Std 1003.1-2001, <fcntl.h>, <unistd.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the  referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                             PIPE(3P)