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Comment by m463 | Hacker News Reader

completion scripts are very very useful, but writing them is a disorganized mess.

It would almost be easier to modify the bash source itself to read and use a regular grammar, say:

  foo [-p <pid>] [-f <configfile>]
  <pid>: {ps -eo pid}
  <configfile>: {ls -1 *.cfg}

or maybe something even nicer with help text

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I wrote long ago about writing competion scripts in any language: https://saveriomiroddi.github.io/Using-scripts-in-any-langua....

Although it's not ideal (one ends up duplicating the arguments parsing logic of the program), it's actually not complicated, just some boilerplate.

well, your completion script doesn't _need_ to be written in bash. If you're writing a completion script for an executable, that executable can be called with an option that generates the completions for bash to consume. You just need to generate the output in the expected format and install a softlink . Hope this can give you some comfort.

Bash completion for the domterm command (a terminal emulator) calls the domterm command itself with a special "#complete-for-bash" option:

    complete -o nospace -C 'domterm "#complete-for-bash" "$COMP_LINE" "$COMP_POINT"' domterm

It works pretty well has the advantage that it automatically ties the completion to the executable, avoiding version mismatches.

It would be great if other shells could use a similar mechanism. Then you could use the same completion logic for multiple shells. A complication is that zsh and fish completion provide descriptive help text; there would need to be a mechanism for a "completion option" to provide such help text.

>It would almost be easier to modify the bash source itself to read and use a regular grammar

It's an interesting idea that we're using for zio-cli [1].

[1] https://github.com/zio/zio-cli/pull/119

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