stream data to stdin of exec about child-process-promise

[patrick-steele-idem]

This module is just a small wrapper around the native child_process module. As such, it just passes along the provided arguments directly to the native exec, execFile or spawn methods. You can use the progress event to access the native child process instance and from there you have access to child.stdin, child.stdout and child.stderr.

Since you have access to the input and output streams of the child process you should be able to do everything that you need. Please take a look at the docs for the child_process module and let me know if you are still stuck or if you think something can be improved in this module.

[fasiha]

Thanks for the pointer Patrick! Please forgive this asinine followup, I'm leaving this here just as a tiny example: I wanted to replicate this node-native functionality:

var spawn = require('child_process').spawn;
var s = "hi there!";
var wc = spawn('wc', []);
wc.stdin.write(new Buffer(s));
wc.stdin.end();
wc.stdout.on('data', function(data) {
  console.log("wc said: " + data);
});

With child-process-promise, this is what that looks like:

var spawn = require('child-process-promise').spawn;
var s = "hi there!";
var p = spawn('wc', [], { capture: ["stdout"] })
            .progress(function(childProcess) {
              childProcess.stdin.write(new Buffer(s));
              childProcess.stdin.end();
            })
            .then(function(results) { return results })
            .fail(function(err) { console.error('[spawn] ERROR: ', err); });
// ...
p.then(function(results) { console.log("wc said: " + results.stdout); })

where the first chunk of code can be in, say, a module, and the last line in a consumer of that module.

🙇!

[patrick-steele-idem]

Hey @jmls and @fasiha. Just throwing this out there, but what if we monkey-patched the returned Promise object to include a childProcess property as shown below:

var spawn = require('child-process-promise').spawn;
var s = "hi there!";
var p = spawn('wc', [], { capture: ["stdout"] })
p.childProcess.stdin.write(new Buffer(s));
p.childProcess.stdin.end();
// ...
p.then(function(results) { console.log("wc said: " + results.stdout); })

The progress event is not part of the native Promise specification (only supported by Q as far as I know). I think monkey-patching the promise object is the lesser of two evils. Any other ideas to simplify the code a bit?

[fasiha]

@patrick-steele-idem that would be much clearer!

(Embarrassed to admit it but I didn't know that progress was a Q thing, I just used it blindly. But I had no problem converting the resulting promise to a bluebird promise using resolve.)