From 5bc3f13b4ff5a231737a9587626c42b0014b080d Mon Sep 17 00:00:00 2001
From: Robin <imer@imer.cc>
Date: Tue, 26 Nov 2013 20:36:53 +0100
Subject: [PATCH] Exit if already running (pid file)

---
 overviewer.py           | 10 ++++++++--
 overviewer_core/util.py | 13 ++++++++++++-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/overviewer.py b/overviewer.py
index 74d4394..b33acfa 100755
--- a/overviewer.py
+++ b/overviewer.py
@@ -141,8 +141,14 @@ def main():
 
     if options.pid:
         if os.path.exists(options.pid):
-            print("Already running (pid exists) - exiting..")
-            return 0
+            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
diff --git a/overviewer_core/util.py b/overviewer_core/util.py
index d936cba..6b81d8b 100644
--- a/overviewer_core/util.py
+++ b/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
\ No newline at end of file