trusty (3) pipe.3posix.gz

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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>


       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 .