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I'm writing a CLI utility called envset, which has this usage: envset [ENVSET-OPTIONS] [SETNAME] [--] [CMD] [ARGS]....
It basically runs a command with a set of environment variables defined in a config file (there's already an npm package with the same name, but I'm implementing my utility in Perl with a different feature set).

I want to provide tab completion for envset. The completion is handled by a shell function _envset. It would be nice in the case like below (^ denotes the location of cursor when Tab is pressed):

% envset mycolors -- ls -^

_envset can return the completion answers for ls instead (so, return a list of possible ls command-line options). Is there an easy way I can ask bash to return them for me?

Otherwise, I'd have to do something like the following in _envset (which is not perfect but should be good enough for most cases):

  1. parse the output of complete to find an entry that describes how a command (in the above example, ls) is completed. If there is none, find the entry with -D (default handler).

  2. if the command is completed by function (-F), call that function (after setting COMP_WORDS and COMP_CWORD appropriately). Return the COMPREPLY from the function.

  3. if the command is completed by external command (-C), run the command (after setting COMP_LINE and COMP_POINT appropriately). Capture the output lines and set COMPREPLY.

  4. and so on for each of the other type of handler (-W, -G, etc). I think handling -F, -C, -W, and -A should cover a majority of the cases.

  5. for the default handler, there's a special case of it returning 124 which means we must restart from step 1 to see if the handler has defined complete for our wanted command.

  • Look at the completion for e.g. sudo. – Michael Homer Aug 5 '17 at 6:44
  • That's what I did before posting this question. I thought that _sudo didn't do the above, but after a second look it turns out it does. Thanks! – Gerry Lufwansa Aug 5 '17 at 7:05

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