Simple snippet for cross-platform .pid management in NodeJS. I use it for managing NodeJS apps with supervisord and monit

pid.js

//
// Usage: require('./pid')("myapp");
//
var fs        = require('fs');

module.exports = function(appname){
  process.title = appname;

  var PID_FILE  = "/usr/local/var/run/"+process.title+".pid";

  fs.writeFileSync(PID_FILE, process.pid+"\n");

  process.on("uncaughtException", function(err) {
    console.error("[uncaughtException]", err);
    return process.exit(1);
  });

  process.on("SIGTERM", function() {
    console.log("SIGTERM (killed by supervisord or another process management tool)");
    return process.exit(0);
  });

  process.on("SIGINT", function() {
    console.log("SIGINT");
    return process.exit(0);
  });

  process.on("exit", function() {
    return fs.unlink(PID_FILE);
  });
  
};

pid_management.coffee

#
# The following snippet must be inserted at the top of your main js file
#

process.title = "MyApp"
PID_FILE      = "/usr/local/var/run/#{process.title}.pid"
fs            = require("fs")

fs.writeFileSync PID_FILE, "#{process.pid}\n"

process.on "uncaughtException", (err) ->
  console.error "[uncaughtException]", err
  process.exit 1

process.on "SIGTERM", ->
  console.log "SIGTERM (killed by supervisord or another process management tool)"
  process.exit 0

process.on "SIGINT", ->
  console.log "SIGINT"
  process.exit 0

process.on "exit", ->
  console.log('Exiting...')
  fs.unlink PID_FILE

#
# Your code start here
#

setInterval (->), 1000

pid_management.js

//
// The following snippet must be inserted at the top of your main js file
//

process.title = "MyApp";

var PID_FILE  = "/usr/local/var/run/"+process.title+".pid"
,   fs        = require('fs');

fs.writeFileSync(PID_FILE, process.pid+"\n");

process.on("uncaughtException", function(err) {
  console.error("[uncaughtException]", err);
  return process.exit(1);
});

process.on("SIGTERM", function() {
  console.log("SIGTERM (killed by supervisord or another process management tool)");
  return process.exit(0);
});

process.on("SIGINT", function() {
  console.log("SIGINT");
  return process.exit(0);
});

process.on("exit", function() {
  return fs.unlink(PID_FILE);
});

//
// Your code start here
//

setInterval(function(){}, 1000);

You should use the unlinkSync on exit, otherwise you'll not granted to have the pid file deleted