If I am at a zsh prompt and I have the current "context" (partially completed command-line command)

% man gr_
        ^ here I have used _ to  represent the cursor 

If I then invoke the _complete_help function CtrlXh

It tells me the context is

% man gr_
tags in context :completion::complete:man::
    manuals  (_man)

If I am reading this output correctly - I can see there is a completer function _man that is capable of listing all the known man pages - which would be invoked if I hit the Tab key at this point.
My question is, can I call the _man completer function manually? rather than having _man being invoked by compsys (which itself is invoked by Tab)?

I have tried using the zle minibuffer <Esc>x , then type _man<Enter> but I think the mini-buffer is only capable of understanding zle commands, not executing general functions.


I found that yes its possible and usable for simple completion functions, but because, this particular function _man does some parsing and validation work, it generates an error when invoked outside of its expected context.

Here's what I did to bind the _man completion function to a key combination so it could be invoked manually.

Define a wrapper function that sets the required options.

_man_autonomous () {
  eval $_comp_setup
  _man "$@"

Register a new widget with the line editor:

zle -C complete-man expand-or-complete _man_autonomous

bind the widget to Ctrl+T

bindkey '^T' complete-man

There is an example of this technique using _files in the zsh FAQ.

  • The problem was nonexistent manpath entries. Completion functions expect a set of options including null_glob and calling individual functions directly does not set those options. See my edit. – Gilles 'SO- stop being evil' Aug 15 '16 at 20:58
  • @Gilles thanks for that. After running the code you provided, I get no response (no errors either). i.e. after running your code in a zsh terminal, I then type: % man gr<CTRL-T> - gives no response. I also tried running in a zsh shell without sourcing my ~/.zshrc and also using an ordinary widget instead of a completion widget i.e. I used zle -N complete-man _man_autonomous. this produced multiple errors e.g. _man:3: bad math expression: operand expected at == (( - 1...' – the_velour_fog Aug 15 '16 at 21:38
  • Did you press Ctrl+T twice? By default expand-or-complete requires this on an ambiguous prefix. You might have Tab bound to a different widget if you don't usually do that (I have it bound to complete-word). – Gilles 'SO- stop being evil' Aug 15 '16 at 21:43
  • @Gilles pressing CTRL-T twice still causes no response. It would be nice if I could just bind to a normal widget, but from your code it seems that _man_autonomous runs in its own context (own process or subshell) for purposes of constraining its scope (not polluting the main parent shell) - it needs to do the setup produced by eval $_comp_setup AND then _man_autonomous needs to be called with arguments which _man "$@" uses. obviously those arguments are normally provided by the completion system upon invocation. – the_velour_fog Aug 15 '16 at 21:54
  • You can't call a completion function outside of a completion context. I have no idea why this doesn't work for you, it works for me on zsh 5.0.7 both with my own configuration and with a .zshrc that contains only autoload -U compinit; compinit and the code in this answer. Try calling set -x and invoking the widget, and reading through the trace (but the trace may be very long, it can be difficult to locate the problem). – Gilles 'SO- stop being evil' Aug 15 '16 at 22:00

I'm not sure why zsh doesn't provide this functionality... Luckily someone made a hack: https://github.com/Valodim/zsh-capture-completion

$ capture.zsh 'man gr'

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