CODEWITHSUNDEEP
javascriptnode.jsgulp
nicholaswmin
nicholaswmin

Reputation: 22939

Start a shell process in Gulp with callback when process started

I'm trying to run some tasks in Gulp, sequentially. One of those tasks is a shell script that performs a simple $ node app.js. How can I fire the callback so I can tell Gulp that the server has started?

tl;dr

So here's the bigger picture of what I'm trying to accomplish:

I'm using gulp run-sequence to fire up a number of tasks sequentially, which specifies a couple ways you should be writing your tasks in order for them to be run in sequence.

Each gulp.task() must either:

My setup:

Here's my spin-server task:

gulp.task("spin-server", function(cb) {
  exec("sh shell-utilities/spin-server");

  // @HACK allow time for the server to start before `runSequence`
  // runs the next task.
  setTimeout(function() {
    cb();
  }, 2500);
});

And here's the spin-server.sh shell script:

## Start Node server ##

node server/app.js

#######
# EOF #
#######

The problem

Right now I'm using a setTimeout hack to make sure my Node/Express server has fired up before proceeding to run the init-browser-sync task.

How can I eliminate that setTimeout hack and call cb() when my Express server actually fires up?

Upvotes: 3

Views: 1559

Answers (4)

Eduardo Cuomo
Eduardo Cuomo

Reputation: 18937

var exec = require('child_process').exec;
 
gulp.task('spin-server', function (cb) {
  exec('sh shell-utilities/spin-server', function (err, stdout, stderr) {
    console.log(stdout);
    console.log(stderr);

    if (err || stdout.indexOf('runSequence') > -1) {
      cb(err);
    }
  });
})

Upvotes: 0

Samuel Bolduc
Samuel Bolduc

Reputation: 19173

Use spawn instead of exec (require('child_process').spawn) like this :

var spawn = require('child_process').spawn;

gulp.task("spin-server", function(cb) {
  var srv = spawn("sh shell-utilities/spin-server");

  srv.stdout.on('data', data => {
    if(data.includes('server listening')) { // Or whatever your server outputs when it's done initializing
      console.log('Server initialization completed');
      return cb();
    }
  });
});

When the string server listening is found in the output of the spawned process, the cb() is called and the server is guaranteed to be initialized at that point.

Upvotes: 3

Iceman
Iceman

Reputation: 6145

gulp.task("spin-server", function(cb) {
  const spawn = require('child_process').spawn;
  const process = spawn('bash', ['', 'setup.sh']);

  process.stdout.on('data', (data) => {
      if(data = "SCRIPT CHECKPOINT")
          cb();
      });
});

Use spawn for non blocking async exec.

Let your setup.sh file print "SCRIPT CHECKPOINT" or something similar to inform that the server is up and running".

This will trigger the cb().

Upvotes: 2

Patrick Goley
Patrick Goley

Reputation: 5417

If you'd like to spawn a process but listen to it's output, you can start it with exec and then attach listeners to the stdout of the process.

var exec = require('child_process').exec;

gulp.task("spin-server", function() {

  var child = exec("sh shell-utilities/spin-server");

  child.stdout.on('data', function(data) {
    console.log('stdout: ' + data);
  });
  child.stderr.on('data', function(data) {
    console.log('stderr: ' + data);
  });
  child.on('close', function(code) {
    console.log('closing code: ' + code);
  });
});

Upvotes: 2

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