os: add os.devnull()

Returns the platform-specific file path of the null device.

Author: lpinca

doc/api/os.md

@@ -122,6 +122,18 @@ The properties included on each object include:
 `nice` values are POSIX-only. On Windows, the `nice` values of all processors
 are always 0.
 
+## `os.devnull()`
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {string}
+
+Returns the platform-specific file path of the null device:
+
+* `\\.\nul` on Windows
+* `/dev/null` on POSIX
+
 ## `os.endianness()`
 <!-- YAML
 added: v0.9.4

lib/os.js

@@ -349,9 +349,18 @@ function userInfo(options) {
   return user;
 }
 
+/**
+ * @returns {'\\.\nul' | '/dev/nul'}
+ */
+function devnull() {
+  return isWindows ? '\\\\.\\nul' : '/dev/null';
+}
+devnull[SymbolToPrimitive] = devnull;
+
 module.exports = {
   arch,
   cpus,
+  devnull,
   endianness,
   freemem: getFreeMem,
   getPriority,

test/parallel/test-os.js

@@ -259,3 +259,13 @@ if (!common.isIBMi) {
 
 is.number(+os.freemem, 'freemem');
 is.number(os.freemem(), 'freemem');
+
+const devnull = os.devnull();
+
+if (common.isWindows) {
+  assert.strictEqual(devnull, '\\\\.\\nul');
+} else {
+  assert.strictEqual(devnull, '/dev/null');
+}
+
+assert.strictEqual(`${os.devnull}`, devnull);