
\S pipe:  |:  pipeline \S


  1.  In a syntax summary, a pipe (|) character between options indicates
    that only one of the options can be used.  For example, [x|y|z]
    indicates that you can use x, or y, or z, but you can't use any of
    them together.

  2.  A pipe is also a program that, when used on a command line, causes
    the output of one command to be used as the input for the next
    command.  You create a pipeline by connecting two or more commands
    with pipes. You do this by preceding each command after the first
    with a  pipe symbol (|).  For example, in the command




            who | wc -l


    the output from who(1), which is a list of users who are logged on to
    the system, is used as input for the word-count command, wc(1).  The
    result of this pipeline is the number of people who are currently
    logged on to the system.  The output for who(1) is not printed to
    standard output, and you do not have to create a temporary file for
    it. The system stores the output in a "buffer"\S*\S until it is
    used for input to the second command.

\S*\S defined in the \Sglossary\S
