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 .