Can now install multiple cleanup handlers

README.md

@@ -12,6 +12,8 @@ npm install node-cleanup --save
 
 nodeCleanup() installs a function that performs cleanup activities just before the node process exits. The cleanup function runs when the process exits normally, when the user presses *ctrl-C*, and when an exception is uncaught. The caller may specify the termination messages to use.
 
+You may call nodeCleanup() multiple times to install multiple cleanup handlers, but only the messages provided with the first call get used.
+
 ```js
 var nodeCleanup = require('node-cleanup');
 
@@ -38,6 +40,8 @@ nodeCleanup(function () {
 
 Install a cleanup handler that reliably runs when node exits. Both parameters are optional. Calling `nodeCleanup()` without a `cleanupHandler` still provides the benefit of ensuring that other installed exit handlers run on *ctrl-C*.
 
+Call this function multiple times to install multiple cleanup handlers. Only the messages provided with the first call are used.
+
 | Param | Description |
 | --- | --- |
 | cleanupHandler | A function that performs the final cleanup of resources before the node process exits. The function may write to `stderr` and `stdout`. It takes no parameters and can't abort the exit. The handler is optional, defaulting to a function that does nothing. |

node-cleanup.js

@@ -4,23 +4,37 @@
  * exits normally, when the user presses ctrl-C, and when an exception is
  * uncaught. The caller may specify the termination messages to use.
  *
+ * Call this function multiple times to install multiple cleanup handlers.
+ * Only the messages provided with the first call are used.
+ *
  * See https://github.com/jtlapp/node-cleanup for more information. Code
  * largely borrowed from http://stackoverflow.com/a/21947851/650894.
  */
+
+var installed = false;
 
 module.exports = function nodeCleanup(cleanupHandler, messages) {
 
+    // attach user callback to the process event emitter.
+    // if no callback, it will still exit gracefully on Ctrl-C
+    cleanupHandler = cleanupHandler || noOp;
+    process.on('cleanup', cleanupHandler);
+
+    // only install the termination handlers once
+    if (!installed) {
+        install(messages);
+        installed = true;
+    }
+};
+
+function install(messages) {
+
     messages = messages || {};
     if (typeof messages.ctrl_C !== 'string')
         messages.ctrl_C = '[ctrl-C]';
     if (typeof messages.uncaughtException !== 'string')
         messages.uncaughtException = 'Uncaught exception...';
 
-    // attach user callback to the process event emitter.
-    // if no callback, it will still exit gracefully on Ctrl-C
-    cleanupHandler = cleanupHandler || noOp;
-    process.on('cleanup', cleanupHandler);
-
     // do app-specific cleaning before exiting
     process.on('exit', function () {
         process.emit('cleanup');
@@ -41,6 +55,6 @@ module.exports = function nodeCleanup(cleanupHandler, messages) {
         }
         process.exit(99);
     });
-};
+}
 
 function noOp() {}; // for just the benefit of graceful SIGINTs