Unix is a Four Letter Word: Unix ---> Others

Unix ---> Other special characters

If you have set the history history) option, you can use special characters to repeat previously entered commands without retyping them. Here are some of them:¹


    !!          On a line by itself will repeat the
                most recent event.
    !com        Will repeat the most recent event
                that begins with "com".
    !?string    Will repeat the most recent event
                that contained "string".
    !-n         Will repeat the nth previous event.
    !n          Will repeat the nth event.  Type
                "history" to see the events numbered.
    ^old^new^   Will substitute "new" for the first
                occurrence of "old" in the most
                recent event, and repeats that event.
    :           Will select specific words from an
                event line so you can repeat parts
                of an event, e.g. 

        !?adam:s/adam/eve/ 

                will substitute "eve" for "adam"
                and repeat the last event with
                "adam" in it.

The semicolon, ";", separates commands. Typing


    clear ; ls

is equivalent to typing each command on a separate command line.

The "&" symbol tells the shell to execute the command in the background. For example, typing xid & would execute XID in the background and give my Unix command line back so I could continue to use it even while XID was running.

The C shell also finds special meaning in the following:


    "  `  {  }  #

Rather than explain the uses of these special characters, I caution you to avoid using them in filenames.

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¹ By event I mean one command line. This may be a single command, or it may include a number of commands in a pipeline, or whatever.

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