CODEWITHSUNDEEP
node.jscommand-line-argumentsstdout
lwood
lwood

Reputation: 275

Getting data into a node script - more complex than command line arguments

I split my tasks into multiple node scripts, "node programs" that will be run individually with node program1.js, node program2.js, etc. using Node's child process exec function in other Node apps.

This way things split up and I can reuse one program in multiple other apps.

It's easy to get data out of a node program like that, you just throw whatever data you want to stdout and have exec capture it on the other end.

For putting data into a node program, how? This is easy if the data is only simple command line arguments, but how would I put arbitrary data (binary, JSON, whatever) into it (at or close the point where I would call exec)? Maybe some piping? Example code I'd appreciate.

Upvotes: 0

Views: 410

Answers (1)

hexacyanide
hexacyanide

Reputation: 91789

Use the env property to pass environment variables to a spawned child process. You can do this in exec(), but for spawning Node processes it's better to use fork(), since it creates a new instance of V8, which is what you're doing.

This is how you'd pass an environment variable:

var exec = require('exec');
var child = exec(command, {
  env: {
    buffer: new Buffer(8),
    json: JSON.stringify(json),
    string: 'a simple string'
  }
}, function(error, stdout, stderr) {
  // execution callback
});

And this is how you'd use the variables in your child process:

process.env.buffer
process.env.json
process.env.string

Upvotes: 1

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