centos man page for pipe

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 correspond-
       ing 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 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(3P)