My 3-line code to copy a directory structure doesn't work

#1

I wrote this dead simple code to reproduce a directory hierarchy:

for dir in $(find @args[1] -type d)
        mkdir -v $( echo $dir | sed "s/@args[1]/@args[2]/" )
end

With mkdir -p src/a src/b I create the following structure:

src/
|-- a
`-- b

I then call my script like so:

./copy_tree.ion src out

This gives me the following error:

mkdir: out
out/b
out: No such file or directory

This equivalent script works in bash and ksh:

for dir in $(find $1 -type d)
do
        mkdir -v $( echo $dir | sed "s/$1/$2/" )
done

I can’t imagine where there could be a mistake. If I replace mkdir -v with another echo in the Ion version, it outputs the correct strings that mkdir needs, yet for some reason when I run the script it doesn’t work.

#2

I found out something related. The command

find . -exec echo {} \;

doesn’t work on a Ion command line (it outputs empty lines). It works in any traditional shell.

Edit: Nevermind. The problem here is that { and } needs to be quoted or escaped with \

#3

After lots of confusion, I figured it out. I just needed to split the arguments. It was right there in the manual. If I had read just a little further it would have saved me hours of debugging.

The correct code:

for dir in @split($(find @args[1] -type d))
        mkdir -v $( echo $dir | sed "s/@args[1]/@args[2]/" )
end
#4

Here’s a more idiomatic version of that code using the replace method.

for dir in @split($(find @args[1] -type d))
        mkdir -v $replace($dir @args[1] @args[2])
end
#5

Thank you for sharing code examples here, it is something I would like to see more of. I am a beginner but hope that seeing snippets of script and code in the conversations will have an effect like that claimed for learning a foreign language - being immersed will allow some of the knowledge to creep in eventually!

Hopefully it is of more immediate use to others too!

#6

Are you reading the manual? There’s only so much you can absorb by osmosis alone, even when talking about foreign languages.

#7

You’re right, although my only interest in languages at the moment is in using C to write keyboard stuff in QMK Firmware, and I don’t think I will be contributing operating system stuff in Rust anytime soon. Hopefully my postings here serve as a demonstration to lurkers that it is not necessary to be some sort of coding guru to join the community and contribute to the discussion!

#8

Oh, well if you become interested in learning Ion I’d be happy to help. I’m almost done studying the manual and I think answering questions would be a great way to test what I’ve learned. It’s a pretty small language and there’s no complicated, low-level, operating system stuff, so it’s pretty easy too.