Help Message for Shell Scripts
source link: https://samizdat.dev/help-message-for-shell-scripts/
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Have you ever thought how good it would be to have a help message for your shell script that you wrote a month ago and already forgot what it is supposed to do?
Yeah, there is always a way to show a message using cat (meow) or a bunch of echo calls.
But there is a neat trick.
Add your message with all the required information on top of your file, just right after the shebang.
#!/bin/bash ### ### my-script — does one thing well ### ### Usage: ### my-script <input> <output> ### ### Options: ### <input> Input file to read. ### <output> Output file to write. Use '-' for stdout. ### -h Show this message.
Halfway done, now need to get this message in runtime with sed.
help() {
sed -rn 's/^### ?//;T;p' "$0"
}
$0
means a filename of a file that is being executed.
A bit about the magic that is going here:
s / ^### ? // T p
Now just call the help
function if an arg -h
or no args passed.
if [[ $# == 0 ]] || [[ "$1" == "-h" ]]; then
help
exit 1
fi
Hope it helps, cheers!
Full gist is available on GitHub: https://gist.github.com/kovetskiy/a4bb510595b3a6b17bfd1bd9ac8bb4a5
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