Question

I have a custom script that takes hostnames as parameters. I know that I can easily copy the existing completion of ssh like this:

compdef myscript=ssh

But that only enables completion of the 1st parameter. Is there an easy way to enable the same completion for all parameters?

Answer 1

I’m not aware of an easy method to enable completion for a custom command. Assuming you’ve got a command foo with a bunch of allowable arguments bar, bas or baz, then the completion is easy: you can either have foo bar, foo bas, or foo baz. If they’re not or‘d, though, you could have any combination of the three.

It gets somewhat worse when you’ve got a ‘depth’ of more than 1 (bar can take arguments car, cas and caz, for example).

In zsh, my general understanding is that completion for commands is detailed in completion functions. These functions are application specific, because the arguments for each application are specific to those applications. As an example, the tmux (a terminal multiplexer, similar to screen, in case you’re not familiar) has a completion function that’s fairly complex: here’s a link.

If you want to write your own completion functions, the documentation is available and accessible. Here are a bunch of links that I’m (slowly) working my way through – they’ll definitely tell you how to get completion working, but there’s a lot of reading. The Z-Shell is a complex beast.

• Z-Shell completion introduction
• Z-Shell functions: Writing and loading your own
• ZSH Users Guide, Ch. 6: “Completion, old and new”

You’re specifically interested in enabling completion for hostname-like arguments, and you’ve singled out ssh as the idea. The zsh completion function for ssh is defined in Completion/Unix/Command/_ssh, if you’ve got the ZSH source. If not, here’s a link.

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Of course, this SO question is rather similar. compdef alone may do what you want, if myscript and ssh parameters are identical enough.