I built a Linux shell that uses Lua instead of bash syntax

hinika — Sun, 19 Jul 2026 13:37:07 +0000

I've been working on wisp, a Linux shell that uses Lua 5.4 for scripting and config instead of inventing another shell grammar.

The core idea is simple: any global function you define in ~/.config/wisp/init.lua becomes a shell command. No alias syntax, no config DSL -- just Lua.

function ll(input)
    return sh("ls -la")
end

function g(input, pattern)
    return sh("grep " .. pattern)
end

Then use them like any command: wisp> ll | g "wisp"

Why Lua?

Every shell invents its own scripting language. Bash has its own grammar, fish has its own, zsh has its own. They all have different syntax for aliases, functions, conditionals, and loops.

Lua is already a real programming language with closures, tables, loops, and a standard library. It's the most embedded scripting language on the planet. Why invent another one?

Structured Pipeline Data

The other thing that's different: native pipeline stages (user-defined functions and builtins) pass Lua tables between each other in-process. No fork, no serialization.

function nums(input)
  return { {n = 3}, {n = 1}, {n = 2} }
end

function sorted(input)
  table.sort(input, function(a, b) return a.n < b.n end)
  return input
end

wisp> nums | sorted passes the table directly from nums to sorted without forking or text parsing. Only when a pipeline hits an external command (grep, wc, anything on $PATH) does wisp fork and serialize to bytes.

What's in v2

Full job control: fg, bg, kill, disown, wait
Globbing, brace expansion
${VAR:-default} expansion
2>&1 redirect
Tab completion for commands, filenames, Lua functions
Levenshtein command-not-found suggestions
Script mode: ./wisp -f script.lua or #!/usr/bin/env wisp
Builtins: cd, exit, export, command, jobs, fg, bg, kill, disown, wait, echo, source, pwd, type

Stats

Binary: 195K (stripped: 168K)
Source: ~2,300 lines C++17
Dependencies: Lua 5.4, vendored linenoise
Startup: 1.5ms

What it can't do (yet)

No array syntax, no [[ ]] tests, no ${!prefix*} expansions. Not a bash replacement for scripts -- focused on interactive use.