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 (con-
       sult 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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                      PIPE(3P)