ideas around scripts with rubyshell in shebang

[jjb]

Intro

Did you know that recent versions of gem have an npx-style way of invoking a gem's script of the same name? So today, this already works 🎉

#!/usr/bin/env gem exec rubyshell exec

sh do
  puts date
  puts pwd
end

# $ chmod +x my_script
# $ ./my_script

Sun Jun  7 10:44:22 PDT 2026
/Users/john/tmp

Idea 1

You can add that to the docs

Idea 2

a "no-sh-block" mode where the entire file is assumed to be rubyshell, no sh do needed. Could implement this with a flag (rubyshell exec --top-level) or simply autodetect when the script runs (check for presence of sh do in the script, either with a simple grep or string search, or maybe fancier way with prism?).

Plot-twist: I lied a little

the actual shebang I used is: #!/usr/bin/env -S RUBYOPT=-W0 gem exec --silent rubyshell exec

RUBYOPT=-W0 and --silent are needed to keep the output nice

maybe that approach is fine or maybe the gem exec feature could be refined, I'm not sure what folks would consider safe as default behavior.

[albertalef]

Wow, thanks for this info! I didnt know about the gem exec.
About some arg to execute without sh block, actually the rubyshell exec already does not need the presence of the sh block.
In the line bin/rubyshell:7 we make the extend of the Executor.

if ARGV.first&.strip&.start_with? "exec"
  extend RubyShell::Executor # rubocop:disable Style/MixinUsage

  load(ARGV.last)

Maybe is missing this info on doc hahaha

[jjb]

the rubyshell exec already does not need the presence of the sh block

nice!

➔ cat my_script
#!/usr/bin/env -S RUBYOPT=-W0 gem exec --silent rubyshell exec

puts date
puts pwd
➔ chmod +x my_script
➔ ./my_script
Thu Jun 11 18:26:28 PDT 2026
/Users/john/tmp