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

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 Technol-
       ogy -- 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(P)