Rebuild auto-complete index (or whatever it's called) and binaries in $PATH cache in zsh

To rebuild the cache of executable commands, use rehash or hash -rf.

Make sure you haven't unset the hash_list_all option (it causes even fewer disk accesses but makes the cache update less often).

If you don't want to have to type a command, you can tell zsh not to trust its cache when completing by putting the following line in your ~/.zshrc¹:

zstyle ":completion:*:commands" rehash 1

There is a performance cost, but it is negligible on a typical desktop setting today. (It isn't if you have $PATH on NFS, or a RAM-starved system.)

The zstyle command itself is documented in the zshmodule man page. The styles values are documented in the zshcompsys and zshcompwid man pages, or you can read the source (here, of the _command_names function). If you wanted some readable documentation… if you find some, let me know!

¹ _{requires zsh≥4.3.3, thanks Chris Johnsen}

If you are having problems getting “argument completion” working for the new commands then compinit is probably the command you need, however it has a caching mechanism that might be causing your problem.

The documentation for my version (4.3.10) says that compinit uses a cached “dump file”, .zcompdump, to store compiled completion functions to speed up subsequent invocations. It only invalidates the dump file when it notices a change in the number of completion files (fpath element files that start with #compdef … or #autoload …). Presumably installing new software would change the number of such completion files (assuming that it also installed its zsh auto-complete files in the right place), so I would expect a plain compinit to work. If you are in a situation where it does not work you may need to bypass or manually invalidate the dump file.

To skip using the dump file, use compinit -D; this will only affect the current shell.

To rebuild the dump file, remove it and rerun compinit:

rm -i ${ZDOTDIR:-${HOME:?No ZDOTDIR or HOME}}/.zcompdump &&
compinit

This will affect the current shell, existing shells that run plain compinit, and any future shells.