launch.py: only add cronjob to crontab if it does not exist

launch.py

@@ -113,10 +113,26 @@ def write_crontab(every_min=5):
     f.write(crontab)
     f.flush()
     f.close()
-    cmd = 'crontab %s' % fpath
+
+    # does the current crontab already exist?
+    cmd = 'crontab -l'
     p = sproc.Popen(cmd, stdout=sproc.PIPE, stderr=sproc.STDOUT, shell=True)
     stdout = p.stdout.readlines()
     p.wait()
+    crontab_exists = False
+    for line in stdout:
+        if line.find(cwd) > -1 and line.find(launch) > -1:
+            # current crontab job is already running!
+            crontab_exists = True
+            break
+
+    if not crontab_exists:
+        cmd = 'crontab %s' % fpath
+        p = sproc.Popen(cmd, stdout=sproc.PIPE, stderr=sproc.STDOUT, shell=True)
+        stdout = p.stdout.readlines()
+        p.wait()
+        print "added launch.py to crontab:"
+        print crontab
 
 def remove_crontab():
     cmd = 'crontab -r'