Section G.



                           INTRODUCTION TO UNIX

                            Useful Mechanisms


       The following character(s) have special meaning and are useful in
       commands that reference files, directories, and pathnames.

       ~      your home directory (C-shell)
       .      present working directory
       ..     parent directory, the directory directly above your current
              working directory

       To copy a file file1 from your home directory to your current
       working directory, enter:

       % cp ~/file1 .

       Pipes (|) allow for buffering of output from one command, as input
       into another.

       Example: To view the long format output of the systems root
                directory one screen full at a time:

       % ls -lR / | more

       A command line may contain several commands, each taking it's
       input from the output of the previous command; these commands are
       then referred to as filters:

       % w | sort | more

       Input/Output (I/O) redirection can be accomplished by using >, >>,
       and <.  If you enter:

       % cat file1 file2 > file3

       the contents of file1 and file2 are written to file3; file3 is
       created or if it exists, it's contents are overwritten

       % cat file1 file2 >> file3

       the contents of file1 and file2 are appended to file3 if it
       exists, if not it is created

       % mail user_name < message.file

       the mail command will take as input message.file and send it to
       user_name.

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