How Bash Completion Works

Re:How Bash Completion Works by shakna on Monday October 07, 2019 @09:55PM (#21187914)

Ok, here's a simpler example that might demonstrate why it can't always be solved.

    ffmpeg -i input.avi -metadata author=shakna output.mp4

What metadata keys are allowed, if at all, actually depends on the output file. If I'd chosen to make an ogv instead, then that metadata flag would become disabled, because it doesn't accept most sets of metadata.

I can't complete:

    ffmpeg -i input.avi -metadata a[TAB]

Because the entire set of CLI commands isn't simple left-to-right solveable.

However, if I do:

    ffmpeg -i input.avi -metadata author=shakna output.mp4 output.ogv

That means I'm outputting one file with metadata, output.mp4, and one file without it, output.ogv. So the flag is conditionally enabled or disabled.

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Re:How Bash Completion Works by vunie on Tuesday October 08, 2019 @08:19PM (#21198695)

I can now see what you meant by completion not being left-to-right solvable. Thanks for taking the time to lay out a clear example.

While completion isn't be solvable in general, surly we can agree that its usefulness (when solvable) merits making it more readily available to users.

Having the shell implementation automatically deduce suggestions from the command itself (when available/possible) would go a long way towards increasing availability in my opinion.

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