pipe

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() .
       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(P)