add something like ruby un.rb or cmake -E for cross platform scripts about crystal HOT 3 OPEN

The way it works in Ruby is through a trick (-run => require "un") then ARGV is made available for the script to interpret. I'm afraid that would be very slow and inefficient in Crystal since it'd have to (re)compile an executable on each and every call.

find-llvm-config doesn't just build on top of a few commands (command, cat, dirname and printf) it also involves control-flow, variables, environment variables, ..., in other words: a programming language of sort.

It could be interesting to have a nanoshell shard that would be compiled once and install itself as bin/nsh to expose some portable commands, but... that still wouldn't be portable, unless it also implements an interpreter.

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Oh, I didn't know about un.rb. Looks interesting, like a mini busybox with a few selected commands.
I do not see how this would be useful for the Crystal compiler, though. With a small scope such as un.rb it would be by far insufficient for implementing relatively straightforward scripts such as find-llvm-config. And with more extensions to make it sufficient for more complex use cases, it'll end up being a complete shell and core utils implementation. That's most certainly out of scope for this project.

I could see some usefulnes for this as an internal tool for stdlib specs to replace a couple of platform-specific test helpers (such as

from crystal.

most shard builds I have seen use make with simple cmds like mkdir -p or cp . This will also help those shards be installable on windows

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