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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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Ash Vs Bash (lemmy.ca)

submitted 1 year ago by danielquinn@lemmy.ca to c/linux@lemmy.ml

10 comments fedilink hide all child comments

[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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[–] danielquinn@lemmy.ca 8 points 1 year ago (3 children)

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 19 points 1 year ago* (last edited 1 year ago) (2 children)

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 3 points 1 year ago (1 children)

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

[–] suprjami@lemmy.sdf.org 10 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.