sudo apt install ruby-full # system ruby, fine for scripts ruby -v; irb # repl gem install bundler --user-install
System gems need sudo (sudo gem install x): prefer gem install –user-install
or rbenv if you need a newer ruby:
# rbenv route (only if system ruby is too old) sudo apt install rbenv ruby-build rbenv install -l | tail # list versions rbenv install 3.3.0 && rbenv global 3.3.0
Ruby one-liners:
ruby -e 'puts File.readlines("f").grep(/error/).size' # count matches ruby -pe 'sub(/foo/, "bar")' -i file.txt # sed-ish in-place ruby -rjson -e 'j=JSON.parse(STDIN.read); puts j["key"]' < f.json
Script skeleton:
#!/usr/bin/env ruby abort "usage: #{$0} FILE" if ARGV.empty? File.readlines(ARGV[0], chomp: true).each { |l| puts l.upcase }
sudo apt install nodejs npm # distro version (older but fine) node -v; node script.js # run node # repl
For a modern Node (nvm is the usual route):
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.0/install.sh | bash nvm install --lts
npm init -y # package.json npm install <pkg> # local dep npx <tool> # run without installing
Node skeleton:
#!/usr/bin/env node
const fs = require("fs");
const [,, file] = process.argv;
if (!file) { console.error("usage: script FILE"); process.exit(1); }
console.log(fs.readFileSync(file, "utf8"));
sudo apt install lua5.4 lua5.4 -i script.lua # run then repl
#!/usr/bin/env lua5.4 for line in io.lines(arg[1]) do print(line:upper()) end
perl -pi -e 's/old/new/g' *.txt # in-place replace across files perl -ne 'print if /error/' log.txt # grep perl -lane 'print $F[2]' data.txt # awk-ish column extract perl -MJSON::PP -0777 -ne 'print decode_json($_)->{key}' f.json