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PIPE(2V)                                                              PIPE(2V)

       pipe - create an interprocess communication channel

       int pipe(fd)
       int fd[2];

       The  pipe()  system  call  creates  an  I/O mechanism called a pipe and
       returns two file descriptors, fd[0] and fd[1].   fd[0]  is  opened  for
       reading  and fd[1] is opened for writing.  The O_NONBLOCK flag is clear
       on both file descriptors (see open(2V)).   When  the  pipe  is  written
       using  the descriptor fd[1] up to {PIPE_BUF} (see sysconf(2V)) bytes of
       data are buffered before the writing process is blocked.  A  read  only
       file  descriptor  fd[0]  accesses  the  data written to fd[1] on a FIFO
       (first-in-first-out) basis.

       The standard programming model is that after the pipe has been set  up,
       two  (or  more)  cooperating  processes (created by subsequent fork(2V)
       calls) will pass data through the pipe using read(2V) and write(2V).

       Read calls on an empty pipe (no buffered data) with only one  end  (all
       write file descriptors closed) returns an EOF (end of file).

       Pipes are really a special case of the socketpair(2) call and, in fact,
       are implemented as such in the system.

       A SIGPIPE signal is generated if a write on a pipe with only one end is

       Upon  successful  completion,  pipe()  marks  for  update the st_atime,
       st_ctime, and st_mtime fields of the pipe.

       pipe() returns:

       0      on success.

       -1     on failure and sets errno to indicate the error.

       EFAULT         The array fd is in an  invalid  area  of  the  process's
                      address space.

       EMFILE         Too many descriptors are active.

       ENFILE         The system file table is full.

       sh(1), fork(2V), read(2V), socketpair(2), write(2V)

       Should more than {PIPE_BUF} bytes be necessary in any pipe among a loop
       of processes, deadlock will occur.

                                21 January 1990                       PIPE(2V)