12. End-to-End Example

This script packages files from dist, writes checksums, and demonstrates common Lash patterns.

#!/usr/bin/env -S lash run

set -euo pipefail
shopt -s nullglob

let dist = "./dist"
let checksum_file = dist + "/SHA256SUMS"

if $(test $"-d \"{dist}\"") != 1
    echo $"missing directory: {dist}"
    exit 1
end

fn checksum(path)
    return $(sha256sum "$path" | cut -d' ' -f1)
end

var count = 0
echo "" > $"{checksum_file}"

for file in ./dist/*.tar.gz
    let sum = checksum(file)
    echo $"{sum}  {file}" >> $"{checksum_file}"
    count += 1
end

if count == 0
    echo "no archives found"
    exit 1
end

echo $"wrote {count} checksums to {checksum_file}"

What this uses

• set and shopt as bare Bash command statements
• immutable let bindings for configuration
• $(test "...") to turn a Bash test into 1 or 0
• a function that returns a value through output
• a glob for loop
• arithmetic +=
• string interpolation
• redirection with > and >>

Check it before running

lash check checksums.lash
lash run checksums.lash

When behavior is unclear, compile the script and inspect the Bash:

lash compile checksums.lash -o checksums.sh
sed -n '1,200p' checksums.sh