Aliases and Variables Keep Things Short and Simple

Tip of the Trade: To save on keystrokes, set up aliases that take command line variables as an argument.
Posted September 4, 2008

Juliet Kemp

Juliet Kemp

Aliases are great for saving typing time, and you probably already have a handful set up. But you may not be aware that it's possible to set up aliases that take command line variables as an argument. Read on for an example.

Note: You can set up the commands given below either directly from the command line or by putting them into your shell config file (e.g., ~/.bashrc or ~/.tcshrc) and then sourcing that.

Occasionally, I want to check which desktop belongs to a particular user. I have a local LDAP directory value set for this, so the command

ldapsearch "(localUser=username)"
does the trick. I want to set up an alias for this, with the command line argument taking the place of username.

In tcsh, this can be done straightforwardly using !:1 for the first argument, !:2 for the second, and so on. Remember, you'll need to escape the ! in the alias definition.

So for my LDAP search:

alias finduser 'ldapsearch "(localUser=!:1)"'
Then the following:
$ finduser username

Unfortunately, in bash/sh/ksh this is no good, as you can't put arguments in aliases. What you can do to produce the same effect is write a function.

function finduser() { ldapsearch "(localUser=$1)"; }
(Note the ; at the end of the command.)

To pass in further arguments to bash, you use $2, $3 and so on. Or, to pass in all the arguments on the command line, $*. This gives much more scop for saving your typing fingers!

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