pipe(2)                                                      pipe(2)


       NAME
             pipe - create an interprocess channel

       SYNOPSIS
             #include <unistd.h>
             int pipe(int fildes[2]);

       DESCRIPTION
             pipe creates an I/O mechanism called a pipe and returns two
             file descriptors, fildes[0] and fildes[1].  The files
             associated with fildes[0] and fildes[1] are streams and are
             both opened for reading and writing.  The O_NDELAY and
             O_NONBLOCK flags are cleared.

             A read from fildes[0] accesses the data written to fildes[1]
             on a first-in-first-out (FIFO) basis and a read from fildes[1]
             accesses the data written to fildes[0] also on a FIFO basis.

             The FD_CLOEXEC flag will be clear on both file descriptors.

             If pipe succeeds, it marks for update the st_atime, st_ctime,
             and st_mtime fields of the pipe.

          Return Values
             On success, pipe returns 0.  On failure, pipe returns -1 and
             sets errno to identify the error.

          Errors
             In the following conditions, pipe fails and sets errno to:

             EMFILE         The maximum number of file descriptors are
                            currently open.

             ENFILE         A file table entry could not be allocated.

       REFERENCES
             fcntl(2), getmsg(2), poll(2), putmsg(2), read(2), sh(1),
             stat(2), streamio(7), write(2)

       NOTICES
             Since a pipe is bi-directional, there are two separate flows
             of data.  Therefore, the size (st_size) returned by a call to
             fstat with argument fildes[0] or fildes[1] is the number of
             bytes available for reading from fildes[0] or fildes[1]
             respectively.  Previously, the size (st_size) returned by a
             call to fstat with argument fildes[1] (the write-end) was the


                           Copyright 1994 Novell, Inc.               Page 1

      pipe(2)                                                      pipe(2)


            number of bytes available for reading from fildes[0] (the
            read-end).  See stat(2).

         Considerations for Threads Programming
            Open file descriptors are a process resource and available to
            any sibling thread; if used concurrently, actions by one
            thread can interfere with those of a sibling.  For example,
            data read from a pipe (destructive) by one thread is not
            available to siblings.







































                          Copyright 1994 Novell, Inc.               Page 2