nshell

scriptable shell written with node

npm install nshell
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nshell

A work-in-progress scriptable shell written with node (replacing bash, ksh, etc).

Installation

$ npm install -g nshell

For now clone and:

$ npm install
$ ./bin/shell

About

Just started this as a quick proof of concept, but it's kinda fun! Keep in mind this is not an attempt to become a POSIX shell.

Features

Small set of features so far:

  • PS1
  • pipelining
  • scriptability!
  • aliases
  • sources ~/.profile.js
  • saves history to ~/.nshell-history
  • brace expansion
  • filename auto-completion
  • some built-ins
  • some magic variables

Built-ins

Currently the following built-ins are available:

  • . -- source a javascript file
  • cd -- change directory
  • which -- search PATH for an executable
  • exit -- exit nshell
  • history -- view history

Variables

Currently the following magic vars are available:

  • $? the exit status of the previous command
  • !! the string value of the previous command

Events

Hook into events with shell.on(event, callback):

  • cd (dir) changing directories
  • exec (line) is about to be executed
  • alias (name, cmd) when an alias is defined
  • source (file, mod) when a module is sourced
  • command (e) when a command line is inputted, but not yet executed

~/.profile.js

By default nshell(1) currently sources ~/.profile.js, this is where you can put config much like other shells.

PS1

Change your PS1 prompt by exporting a string:

exports.PS1 = "tj> ";

Or create something more dynamic and fancy by exporting a function:

var colors = [31, 32, 33, 34, 35, 36];

exports.PS1 = function(){
  var color = colors[Math.random() * colors.length | 0];
  return '\033[' + color + 'm>\033[m ';
};

Brace expansion

Brace expansion works as you'd expect:

> touch foobar
> touch foobaz
> rm foo{bar,baz}

Sourcing

You may source files much like you do with require() in node, support you have "test.js", you may load it with either of the following:

▸ . test.js
▸ . test

Aliases

shell.alias('GET', 'burl GET');
shell.alias('HEAD', 'burl -I');
shell.alias('POST', 'burl POST');
shell.alias('PUT', 'burl PUT');
shell.alias('PATCH', 'burl PATCH');
shell.alias('DELETE', 'burl DELETE');
shell.alias('DEL', 'burl DELETE');
shell.alias('OPTIONS', 'burl OPTIONS');

Debugging

$ DEBUG=nshell ./bin/shell
▸ cat Readme.md
  nshell cmd [{"name":"cat","argv":["Readme.md"]}] +1.1m
  nshell env {} +0ms
  nshell which cat +0ms
  nshell found /bin/cat +2ms
  nshell spawn /bin/cat ["Readme.md"] +0ms
  nshell exit 0 +5ms
  nshell prompt +0ms

Examples

Some cool examples showing off the power of scripting your shell!

Auto-cd

By default nshell(1) does not auto-chdir when the given line is a directory, however you can easily script this in:

var fs = require('fs')
  , exists = fs.existsSync
  , stat = fs.statSync;

// auto-cd

shell.on('command', function(e){
  var path = e.line.trim();
  if (exists(path) && stat(path).isDirectory) {
    e.preventDefault();
    shell.exec('cd "' + path + '"');
  }
});

Usage:

▸ pwd
/Users/tj/projects/nshell
▸ node_modules/commander
▸ pwd
/Users/tj/projects/nshell/node_modules/commander
▸ ../..
▸ pwd
/Users/tj/projects/nshell

Auto-edit

By default nshell(1) will simply give you a "command not found" error if you try to type a filename, however you can script in the ability to edit that file depending on its mime type:

// $ npm install mime

var path = require('path');
var mime = require('mime');

// auto-editor (silly implementation)

shell.on('command', function(e){
  var line = e.line.trim();
  var type = mime.lookup(line);
  switch (type) {
    case 'text/plain':
    case 'text/css':
    case 'application/javascript':
      e.preventDefault();
      shell.exec('mate "' + line + '"');
      break;
  }
});

Command replay

To replay the previous command on a blank line you can also listen on the "command" event and use the shell.lastCommand property, which is populated by the last successfully executed command line.

shell.on('command', function(e){
  if ('' == e.line.trim()) {
    e.preventDefault();
    shell.exec(shell.lastCommand);
  }
});

JavaScript expansion

Modifications to e.line are accepted by nshell, this means you can progressively layer on plugins, in this case a naive implementation of "js expansion":

shell.on('command', function(e){
  e.line = expansion(e.line);
});

function expansion(line) {
  return line.replace(/`(.*?)`/, function(_, js){
    return eval('(' + js + ')');
  });
}

Usage:

▸ echo `Math.pow(2, 32)`
▸ 4294967296
▸ cat `"Make" + "file"`

test:
    @./node_modules/.bin/mocha \
        --require should \
        --reporter spec
...

License

(The MIT License)

Copyright (c) 2012 TJ Holowaychuk <tj@vision-media.ca>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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