Fix #3407 os.tmpDir()

doc/api/os.markdown

@@ -6,6 +6,10 @@ Provides a few basic operating-system related utility functions.
 
 Use `require('os')` to access this module.
 
+## os.tmpDir()
+
+Returns the operating system's default directory for temp files.
+
 ## os.hostname()
 
 Returns the hostname of the operating system.

lib/os.js

@@ -30,13 +30,22 @@ exports.cpus = binding.getCPUs;
 exports.type = binding.getOSType;
 exports.release = binding.getOSRelease;
 exports.networkInterfaces = binding.getInterfaceAddresses;
+
 exports.arch = function() {
   return process.arch;
 };
+
 exports.platform = function() {
   return process.platform;
 };
 
+exports.tmpDir = function() {
+  return process.env.TMPDIR ||
+         process.env.TMP ||
+         process.env.TEMP ||
+         (process.platform === 'win32' ? 'c:\\windows\\temp' : '/tmp');
+};
+
 exports.getNetworkInterfaces = function() {
   return exports.networkInterfaces();
 };

test/simple/test-os.js

@@ -27,6 +27,18 @@ var assert = require('assert');
 var os = require('os');
 
 
+process.env.TMPDIR = '/tmpdir';
+process.env.TMP = '/tmp';
+process.env.TEMP = '/temp';
+var t = ( process.platform === 'win32' ? 'c:\\windows\\temp' : '/tmp' );
+assert.equal(os.tmpDir(), '/tmpdir');
+process.env.TMPDIR = '';
+assert.equal(os.tmpDir(), '/tmp');
+process.env.TMP = '';
+assert.equal(os.tmpDir(), '/temp');
+process.env.TEMP = '';
+assert.equal(os.tmpDir(), t);
+
 var hostname = os.hostname();
 console.log('hostname = %s', hostname);
 assert.ok(hostname.length > 0);