Add some posix functions

Lib/test/test_posix.py

 "Test posix functions"
 
 from test import support
 
 # Skip these tests if there is no posix module.
 posix = support.import_module('posix')
 
 import errno
 import sys
 import time
@@ skipping 140 matching lines @@
                 posix.fexecve(fp, [sys.executable, '-c', 'pass'], os.environ)
             else:
                 self.assertEqual(os.wait(), (pid, 0))
         finally:
             os.close(fp)
 
     @unittest.skipUnless(hasattr(posix, 'gethostid'), "test needs posix.gethostid()")
     def test_gethostid(self):
         self.assertTrue(isinstance(posix.gethostid(), int))
 
-    @unittest.skipUnless(hasattr(posix, 'sethostname'), "test needs posix.sethostname()")
-    def test_sethostname(self):
-        import socket
-        oldhn = socket.gethostname()
-        try:
-            posix.sethostname('new')
+    @unittest.skipUnless(hasattr(posix, 'sethostid'), "test needs posix.sethostid()")
+    def test_sethostid(self):
+        hid = os.gethostid()
+        try:
+            posix.sethostid(2464787)
         except OSError as e:
-            self.assertEqual(e.errno, errno.EPERM)
+            if sys.platform.startswith("freebsd"):
+                self.assertEqual(e.errno, errno.EPERM)
+            else:
+                self.assertEqual(e.errno, errno.EACCES)
         else:
             # running test as root!
-            self.assertEqual(socket.gethostname(), 'new')
-            posix.sethostname(oldhn)
+            self.assertEqual(os.gethostid(), 2464787)
+            posix.sethostid(hid)
 
     @unittest.skipUnless(hasattr(posix, 'waitid'), "test needs posix.waitid()")
     @unittest.skipUnless(hasattr(os, 'fork'), "test needs os.fork()")
     def test_waitid(self):
         pid = os.fork()
         if pid == 0:
             os.chdir(os.path.split(sys.executable)[0])
             posix.execve(sys.executable, [sys.executable, '-c', 'pass'], os.environ)
         else:
             res = posix.waitid(posix.P_PID, pid, posix.WEXITED)
-            self.assertEqual(pid, res[3])
+            self.assertEqual(pid, res.si_pid)
 
     @unittest.skipUnless(hasattr(posix, 'lockf'), "test needs posix.lockf()")
     def test_lockf(self):
         fd = os.open(support.TESTFN, os.O_WRONLY | os.O_CREAT)
         try:
             os.write(fd, b'test')
             os.lseek(fd, 0, os.SEEK_SET)
             posix.lockf(fd, posix.F_LOCK, 4)
             # section is locked
             posix.lockf(fd, posix.F_ULOCK, 4)
@@ skipping 393 matching lines @@
         for groups in [[0], list(range(16))]:
             posix.setgroups(groups)
             self.assertListEqual(groups, posix.getgroups())
 
 
 def test_main():
     support.run_unittest(PosixTester, PosixGroupsTester)
 
 if __name__ == '__main__':
     test_main()