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Ash Vs Bash (lemmy.ca)
submitted 1 year ago by danielquinn@lemmy.ca to c/linux@lemmy.ml

[For reference, I'm talking about Ash in Alpine Linux here, which is part of BusyBox.]

I thought I knew the big differences, but it turns out I've had false assumptions for years. Ash does support [[ double square brackets ]] and (as best I can tell) all of Bash's logical trickery inside them. It also supports ${VARIABLE_SUBSTRINGS:5:12}` which was another surprise.

At this stage, the only things I've found that Bash can do that Ash can't are:

  • Arrays, which Bash doesn't seem to do well anyway
  • Brace expansion, which is awesome but I can live without it.

What else is there? Did Ash used to be more limited? The double square bracket thing really surprised me.

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[-] suprjami@lemmy.sdf.org 15 points 1 year ago* (last edited 1 year ago)

What have you found bad about bash arrays? I have some simple usage of those (in bash) and they work fine.

[-] danielquinn@lemmy.ca 8 points 1 year ago

As far as I've seen, they don't provide any advantage over a string with spaces, which doesn't work well either when you've got values with spaces:

not_what_you_think=( "a b" "c" "d" )
for sneaky in ${not_what_you_think[@]}; do
  echo "This is sneaky: ${sneaky}"
done
This is sneaky: a
This is sneaky: b
This is sneaky: c
This is sneaky: d
[-] shmanio@lemmy.world 21 points 1 year ago* (last edited 8 months ago)

You should put some quotes where you use the array:

not_what_you_think=( "a b" "c" "d" )
for sneaky in "${not_what_you_think[@]}"; do
  echo "This is sneaky: ${sneaky}"
done

This is sneaky: a b
This is sneaky: c
This is sneaky: d
[-] danielquinn@lemmy.ca 4 points 1 year ago

Aaaaah! Thank you kind stranger. It never would have occurred to me to quote an array!

[-] suprjami@lemmy.sdf.org 11 points 1 year ago

If you run your scripts through https://shellcheck.net it'll pick up things like this. Also available as a Linux package for offline use.

[-] zatanas@lemm.ee 6 points 1 year ago

I too would like to know. Thank you.

this post was submitted on 02 Nov 2023
34 points (97.2% liked)

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