Is it POSIX-compatible?

No, deliberately — but the common idioms translate.

What tools are on PATH?

coreutils, sed, grep, awk. No network tools.

Fish · online compiler

Run Fish online

Run Fish 3 shell scripts online — Friendly Interactive Shell, sandboxed.

Version

Fish 3

Firecracker microVM live per-test verdicts multi-file compile

Fish is the "friendly interactive shell" that started as a rebellion against decades of POSIX-shell footguns. Its scripting language is closer to what a modern shell would look like if bash didn't exist.

ls-judge runs Fish 3.x scripts inside a Firecracker microVM.

Starter code

What you get in Fish

Clicking "Run now" opens the playground with this exact code and a matching test case pre-loaded — passes on first Run.

fish

Fish 3

read n
echo (math $n \* 2)

stdin →

expected →

FAQ

Common questions about Fish on ls-judge

Fish 3.x?: Yes.
Is it POSIX-compatible?: No, deliberately — but the common idioms translate.
What tools are on PATH?: coreutils, sed, grep, awk. No network tools.
Free?: Yes.