Hooking into Node.js stdout

gistfile1.js

var util = require('util')

function hook_stdout(callback) {
    var old_write = process.stdout.write

    process.stdout.write = (function(write) {
        return function(string, encoding, fd) {
            write.apply(process.stdout, arguments)
            callback(string, encoding, fd)
        }
    })(process.stdout.write)

    return function() {
        process.stdout.write = old_write
    }
}

console.log('a')
console.log('b')

var unhook = hook_stdout(function(string, encoding, fd) {
    util.debug('stdout: ' + util.inspect(string))
})

console.log('c')
console.log('d')

unhook()

console.log('e')
console.log('f')

This one works with AWS Lambda:

function hookStdout(callback) {
  const boundProcessStdout = process.stdout.write.bind(process.stdout)
  const boundProcessStderr = process.stderr.write.bind(process.stderr)

  process.stdout.write = (string, encoding, fd) => {
    boundProcessStdout(string, encoding, fd)
    callback(string, encoding, fd, false)
  }

  process.stderr.write = (string, encoding, fd) => {
    boundProcessStderr(string, encoding, fd)
    callback(string, encoding, fd, true)
  }

  return () => {
    process.stdout.write = boundProcessStdout
    process.stderr.write = boundProcessStderr
  }
}

thanks for this.

Thank you so much for this! I'm trying to make an advanced CLI for a nextjs app, but webpack uses stdout and messes up all of the formatting!