[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.

  • Daniel QuinnOPEnglish
    00·
    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
    • shmanioEnglish
      10·
      1 year ago7 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