tab completion helpers, for node cli programs. Inspired by npm completion
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An npm package to do some custom command line<tab><tab> completion for any system command, using the node api and JS to provide your own completion, for both bash/zsh shell.

Made possible using the same technique as npm (whose completion is quite awesome) relying on a bash/zsh completion shell script bridge to do the actual completion from node's land.


Latest released version (when it'll get released)

npm install tabtab

Latest dev code:

npm install


You can add completion pretty easily in your node cli script:

#!/usr/bin/env node
var tabtab = require('tabtab');

if(process.argv.slice(2)[0] === 'completion') return tabtab.complete('pkgname', function(err, data) {
  // simply return here if there's an error or data not provided.
  // stderr not showing on completions
  if(err || !data) return;

  if(/^--\w?/.test(data.last)) return tabtab.log(['help', 'version'], data, '--');
  if(/^-\w?/.test(data.last)) return tabtab.log(['n', 'o', 'd', 'e'], data, '-');

  tabtab.log(['list', 'of', 'commands'], data);

// The rest of your script

Simply replace pkgname by the name of your package. The complete callback get's called with data only in the context of a completion command.

The data object holds interesting value to drive the output of the completion:

  • line: full command being completed
  • words: number of word
  • point: cursor position
  • partial: tabing in the middle of a word: foo bar baz bar foobarrrrrrr
  • last: last word of the line
  • lastPartial: last partial of the line
  • prev: the previous word

completion install

Installing the completion for your cli app is done very much like npm does:

. <(pkgname completion)

It'll enables tab-completion for the pkgname executable. Adding it to your ~/.bashrc or ~/.zshrc will make the completions available everywhere (not only the current shell).



Main completion method, has support for installation and actual completion.

tabtab.complete(completed, completer, callback);
  • completed: name of the command to complete
  • completer: Optional name of the command to call on completion (when not set, completed and completer are the same)
  • callback: get called when a tab-completion command happens.

completed and completer are there only to set up and build the correct bash/zsh script, based on the lib/ template (which is based on npm's completion shell script)


Helper to return completion output and log to standard output.

tabtab.log(['list', 'of', 'values'], data, prefix);
  • values: Array of values to complete against.
  • data: the data object returned by the complete callback, used mainly to filter results accordingly upon the text that is supplied by the user.
  • prefix: Optional a prefix to add to the completion results, useful for options to add dashes (eg. - or --).


Helper to return the list of short and long options, parsed from the usual --help output of a command (cake/rake -H, vagrant, commander -h,, ...)

var parsed = completion.parseOut(;

Using a spawned process:

exec('rake -H', function(err, stdout, stderr) {
  if(err) return;
  var parsed = parseOut(stdout);
  if(/^--\w?/.test(o.last)) return log(parsed.longs, data, '--');
  if(/^-\w?/.test(o.last)) return log(parsed.shorts, data, '-');


same purpose as parseOut, but for parsing tasks from an help command (cake/rake -T, vagrant, etc.)

exec('cake', function(err, stdout, stderr) { if(err) return; var parsed = tasks = parseTasks(stdout, 'cake'); log(tasks, o); });

  • stdout: string of help output.
  • prefix: prefix used internally to build the RegExp that is used to parse tasks from stdout.


npm does pretty amazing stuff with its completion feature. Bash and zsh provides command tab-completion, which allow you to complete the names of commands in your $PATH. Usually these functions means bash scripting, and in the case of npm, it is partially true.

There is a special npm completion command you may want to look around, it not already.

npm completion

Running this should dump this script to the console. This script works with both bash/zsh and map the correct completion functions to the npm executable. These functions takes care of parsing the COMP_* variables available when hitting TAB to complete a command, set them up as environment variables and run the npm completion command followed by -- words where words match value of the command being completed.

This means that using this technique npm manage to perform bash/zsh completion using node and JavaScript. Actually, the comprehensiveness of npm completion is quite amazing.

This whole package/module is based entirely on npm's code and @isaacs work.