Shell command execution

Question

I'm trying to implement shell command execution I found here: node.js shell command execution

So I'm trying to get second answer (by Chris Eineke) working. But for now I get no output.

Here is my try:

run_cmd = (cmd, args, done) ->
    spawn = require('child_process').spawn
    child = spawn(cmd, args)
    result = { stdout: '' };
    child.stdout.on \data ! (buffer) -> 
       result.stdout += buffer
    child.stdout.on \end !-> done()
    result

dir = run_cmd(
    'ls', ['-a']
    , !-> console.log('done')
    )

console.log dir.stdout

it compiles to:

  run_cmd = function(cmd, args, done){
    var spawn, child, result;
    spawn = require('child_process').spawn;
    child = spawn(cmd, args);
    result = {
      stdout: ''
    };
    child.stdout.on('data', function(buffer){
      result.stdout += buffer;
    });
    child.stdout.on('end', function(){
      done();
    });
    return result;
  };
  dir = run_cmd('ls', ['-a'], function(){
    console.log('done');
  });
  console.log(dir.stdout);

But I can't see ls results. Where is my mistake? Or what am I doing wrong?

Answer 1

You're not seeing results because run_cmd runs async and the result is empty when console.log dir.stdout is ran. You should rather pass the results to your callback and do the logging there. Here's a working LiveScript version:

run_cmd = !(cmd, args, done) ->
  spawn = require 'child_process' .spawn
  child = spawn cmd, args
  result = stdout: ''
  child.stdout
    ..on \data !(buffer) ->
      result.stdout += buffer
    ..on \end !->
      done result

<-! run_cmd \ls <[ -a ]>
console
  ..log \done
  ..log it.stdout

Here we see multiple LS features used like paren-free chaining (spawn line), braceless object definition (result line), cascades (the ..on and ..log lines), backcalls (<-!), word arrays (<[ array of words ]>) and implicit argument (it). For more info on them, refer to the LiveScript documentation.