| suicidaleggroll |
11-14-2012 12:50 PM |
Quote:
Originally Posted by mfirth
(Post 4829395)
Sorry to resurrect this again, but another possible use for "kill -0" (or more likely the system API equivalent) is to check the existence of a process before communicating with it in another way - e.g.
If service X writes its process ID into /var/run/X.pid, then you can use 'kill -0 `cat /var/run/X.pid`' to determine if the process for X is still running.
There are obviously other ways of doing it (e.g. checking for the PID in /proc, or using grep on the output of PS), but they are probably less elegant
Hope this is useful
Michael
|
Or you could do the same thing by looking at the exit code of "ps -p PID".
Personally, when I'm checking if a process exists, I run "output=$(ps -p PID)", check the exit code, and if it's 0 (process is running), I go on to parse $output for the actual process name to ensure it's the right process using that PID.
Otherwise you can get a false positive when a process writes out its PID, stops running, and hours later some other process happens to be assigned the same PID. Just checking the exit code of "kill -0 PID" or "ps -p PID" in this case will tell you your process is running when it's really not, it could have exited long ago and now something else has simply been assigned that same PID. |
