feat: export ENV vars command line clap2env tool

[dzmitry-lahoda]

flow considered

1. use config of CLI defined in TOML/YAML file
2. parse command line parameters
3. export CONSTANT_CASE ENV vars.
4. so any script/app running after can access to ENV vars parsed

https://discourse.nixos.org/t/nix-bash-maxi-declaratively-configured-cli-args-to-env-vars-tool/37735

Run example.sh --some-par=42:

SOME_PAR=13 clap2env clap-config.toml $@

echo $SOME_PAR

will give

42

[dzmitry-lahoda]

will donate 100 USD in crypto for such tool :)

[epage]

I believe there is a tool that wraps clap for use in bash. Not finding it atm but on mobile.

One challenge with the suggested approach is that the tool can't modify the outside environment. It could dump a script to be sourced or it can wrap a command.

[dzmitry-lahoda]

I believe there is a tool that wraps clap for use in bash. Not finding it atm but on mobile.

Yeah, I searched various terms, not found yet.

I am ok with Go/C/Zig/AOT compiled bytecode - as long as startup is fast.

I just found that clap seems fits as per clap-serde crate already does half of work.

[dzmitry-lahoda]

One challenge with the suggested approach is that the tool can't modify the outside environment. It could dump a script to be sourced or it can wrap a command.

yeah, i see.

so it can be something like:

# bash is bad here, but kind of this to work
source < $(clap2nix clap-config.toml $@)

https://unix.stackexchange.com/questions/125110/how-do-i-source-another-processs-environment-variables

and other option try work:

# so not clear how process reuse shell called it - seems not great until there is 100% portable robust cargo to handle that
clap2nix clap-config.toml $@ -- echo $SOME_PAR