    PIPE(II)                      8/5/73                     PIPE(II)

    NAME
         pipe - create an interprocess channel

    SYNOPSIS
         (pipe = 42.)
         sys pipe
         (read file descriptor in r0)
         (write file descriptor in r1)

         pipe(fildes)
         int fildes[2];

    DESCRIPTION
         The pipe system call creates an I/O mechanism called a pipe.
         The file descriptors returned can be used in read and  write
         operations.   When  the pipe is written using the descriptor
         returned in r1 (resp. fildes[1]), up to 4096 bytes  of  data
         are  buffered  before  the  writing process is suspended.  A
         read using the descriptor returned in r0  (resp.  fildes[0])
         will pick up the data.

         It  is  assumed that after the pipe has been set up, two (or
         more) cooperating  processes  (created  by  subsequent  fork
         calls)  will  pass data through the pipe with read and write
         calls.

         The Shell has a syntax to set up a linear array of processes
         connected by pipes.

         Read calls on an empty pipe (no buffered data) with only one
         end (all write file descriptors closed)  return  an  end-of-
         file.  Write calls under similar conditions generate a fatal
         signal (signal(II)); if the signal is ignored, an error  is
         returned on the write.

    SEE ALSO
         sh(I), read(II), write(II), fork(II)

    DIAGNOSTICS
         The  error  bit (c-bit) is set if too many files are already
         open.  From C, a -1 returned value indicates  an  error.   A
         signal  is  generated if a write on a pipe with only one end
         is attempted.

    BUGS

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