Getting Started with Completion

There are many ways to specify completion on the command line. We'll talk about only one main form in this workshop that should get you comfortable with completion. When you are ready for more, see the man page, or come back to this workshop in a few weeks. (When more will be added)

The syntax of the form we'll discuss is essentially:

compctl [ -CDT ] options [command ...]

Completion definitions start with the command compctl on the command line.
Completion definitions end with the names of command(s) you'd like to complete.
The list of options specify all types of items you'd like eligible for completion. (Variables, options, filenames, jobs, etc.)

You can see all current definitions in a short form by typing compctl with no arguments.

Some examples

Let's try an example. You have a certain set of hosts you like to login to often. A lot of the names are long and cumbersome to type. You'd like to be able to type only a couple of characters and then hit < TAB > to have zsh finish the hostname for you. First, we place a list of hosts that we want to complete in a file, one per line, and call it comp_login_cmds:

> cat ./zsh/comp_login_cmds
www.nebcorp.com
www.acm.uiuc.edu
schrof.net
www.meat.net
www.zsh.org
>

Now for the command line. Let's throw in some cool tricks, too. We'll start with the full command line, and break it down:

compctl -k "( ` < ./zsh/comp_login_cmds `)" telnet rlogin rsh ssh

Now, we look at the command line above:

comptctl starts off the definition
telnet rsh rlogin ssh are the commands that this completion will work for.
The -k says that the items that will be used for completion will come from an array. With -k, the array following is either the name of an array, or an actual array definition inside double-quotes.
The backticks (` `) run a command in zsh, and replace the command output on the command line.
In zsh, a left arrow (input redirector) without a command runs cat on its arguments. Above, therefore, zsh runs the command cat ./zsh/comp_login_cmds and the output gets placed on the command line.
Assuming we have a list of hosts in comp_login_cmds, the command line now internally looks like:
compctl -k "( www.nebcorp.com www.acm.uiuc.edu schrof.net www.meat.net www.zsh.org)" telnet rlogin rsh ssh

There you have it. Now, you can type:

> ssh www.< TAB >

and zsh will present you with all items that start with www. If you had entered:

> ssh www.a< TAB >

zsh would know that there is only one item that starts with www.a, and therefore replace it with www.acm.uiuc.edu