Exit if already running (pid file)

overviewer.py

@@ -141,8 +141,14 @@ def main():
 
     if options.pid:
         if os.path.exists(options.pid):
+            try:
+                with open(options.pid, 'r') as fpid:
+                    pid = int(fpid.read())
+                    if util.pid_exists(pid):
                         print("Already running (pid exists) - exiting..")
                         return 0
+            except IOError, ValueError:
+                pass
         with open(options.pid,"w") as f:
             f.write(str(os.getpid()))
     # if --check-terrain was specified, but we have NO config file, then we cannot

overviewer_core/util.py

@@ -24,7 +24,7 @@ import platform
 from string import hexdigits
 from subprocess import Popen, PIPE
 from itertools import cycle, islice, product
-
+import errno
 def get_program_path():
     if hasattr(sys, "frozen") or imp.is_frozen("__main__"):
         return os.path.dirname(sys.executable)
@@ -391,3 +391,14 @@ try:
     OrderedDict = collections.OrderedDict
 except (ImportError, AttributeError):
     pass
+
+def pid_exists(pid): # http://stackoverflow.com/a/6940314/1318435
+    """Check whether pid exists in the current process table."""
+    if pid < 0:
+        return False
+    try:
+        os.kill(pid, 0)
+    except OSError, e:
+        return e.errno != errno.ESRCH
+    else:
+        return True