Creates a temporary mailbox that can be used to read and write
    data between a parent and child process. The channels through
    which the processes communicate are called a pipe.

    Format

      #include  <unistd.h>

      int pipe  (int array_fdscptr[2]); (ISO POSIX-1)

      int pipe  (int array_fdscptr[2], . . . ); (DEC C Extension)