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Comment by ropeladder | Hacker News Reader

This. I would love to be able to type "[command] --[tab]" and have it list all the options, and/or common options, so when I'm learning 'tar' I don't have to start typing, realize I've forgotten the command, and then have to go use man or --help or go Google it.

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Pretty much any modern shell (bash, zsh, fish, etc) provides command line completion.

If you really think the completion in current shells is the best there can be then I think you lack imagination.

I don't want remembered commands, I want the terminal to tell me what stuff means. I want it to tell me what makes sense in which context. Like the IntelliSense when coding Java or C#. Docs at your fingertips, all relevant options (and none else) available, etc. This is incomparable to the kind of autocomplete any shell I've seen to date has. Zsh is a nice step in the right direction but it's still shit.

fish shell does exactly what you say, out of the box. c/p below:

  ~/.l/share: tar --<tab>                                                               
  --absolute-paths               (Don't strip leading /)
  --after-date                   (Only store newer files)
  --append                       (Append files to archive)
  --atime-preserve               (Keep access time)
  …and 58 more rows

As others have mentioned, zsh can be tuned to perform similarly. fish is nice in that if you don't have explicit completions for options set up it actually parses man pages.

Of course you could always do better, but the specific feature mentioned in the parent comment (completing flags for "tar" instead of checking the man page) has been around for ages.

Regarding contextual analysis, the fundamental problem is that command execution relies on a list of strings (argv) with no types or meaning. Each command is responsible for parsing its own arguments, either manually or using a shared library (e.g. getopt). This provides loose coupling and flexibility, but makes introspection really difficult, and features like completions become an afterthought reimplemented in every shell either by special cases for each command or hacks like parsing help messages.

Have you checked out ZSH? It can do this nicely.

zsh via its ultra-tunable completions can do only 1st part of op's request i.e command option completion, but not the second part i think...

for example, i do the following:

    anupam@virat ~ % autoload -Uz compinit
    anupam@virat ~ % compinit
    anupam@virat ~ % git a<TAB>
    add        -- add file contents to index
    am         -- apply patches from a mailbox
    apply      -- apply patch to files and/or to index
    archimport -- import an Arch repository into git
    archive    -- create archive of files from named tree

edit-001: added trivial example.

My (pretty much vanilla) zsh works quite nicely

https://i.imgur.com/SZqu63p.png

I'm not sure it covers all of the obscure commands you can think of, but 99% of the time it's great.

As far as I can remember the only standard command I use and that my ZSH has trouble with is `dd`. Luckily, its arguments aren't that complicated.

My zsh autocompletion list for git add actually contains the stageable files. I don't know if this is stock zsh behaviour or related to my prezto https://github.com/sorin-ionescu/prezto config but it can be done

Edit: looks like it might be stock behaviour https://github.com/zsh-users/zsh/blob/master/Completion/Unix...

Weird. I'm using Zsh and I swear I've tried that before with nothing happening, but it does actually work. Thanks!

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