Unix in a Nutshell, 4th Edition

Special Aliases

Certain special aliases can be set in tcsh. The aliases are initially undefined. Once set, the commands they specify are executed when specific events occur. The following is a list of the special aliases and when they are executed:

beepcmd

At beep.

cwdcmd

When the current working directory changes.

jobcmd

Before running a command or before its state changes. Like postcmd, but does not print built-ins.

helpcommand

Invoked by the run-help editor command. See the tcsh manpage for details.

periodic

Every few minutes. The exact amount of time is set by the tperiod shell variable.

precmd

Before printing a new prompt.

postcmd

Before running a command.

shell program

If a script does not specify a shell, interpret it with program, which should be a full pathname.

Examples

Demonstrate the cwdcmd alias:

    [arnold@mybox ~]$ alias cwdcmd 'echo now in $PWD'        
                     Set alias
    [arnold@mybox ~]$ cd /tmp                                
                     Change directory
    now in /tmp                                              Output from alias
    [arnold@mybox /tmp]$ cd                                  
                     Change back home
    now in /home/arnoldOutput from alias

Demonstrate the postcmd alias:

    [arnold@mybox ~]$ alias postcmd 'echo now starting\!'    
                     Set alias
    [arnold@mybox ~]$ ls -FC *.txt                           
                     Run a command
    now starting!                                            Output from alias
    adr.gdb.backcover.txt  gdb.backcover.txt  sol-d1-2.txt   Output from command
    awkhomepage.txt        sol-d1-1.txt