Sorry for posted a wrong file earlier!
Hi! Netlander, Sorry to return to all of u lately.
First I have to thank all of u who replied/helped. Thank U!
Here is the summary of the replies regarding detection of process
status. Basically, I am designing a super-server to create/monitor/destroy
server processes. My main objective of monitoring the status of server
processes is detect crash of any server process. Here, I will refer polled
process as server, the process monitoring the status of the server processes
as manager.
1) Using kill():
This is the most popular way (judged from the number of
replies). However, I did not adopt this technique because of the
problem that the effective user ID of the server must be the same as
the manager , which is quite impossible to impose in my server
manager design. Moreover, kill() may not work when the server process
crashes and its process ID is re-assigned to other process.
2) Search the kernel process table (/dev/kmem):
This approach is too OS specific. Portability will be a big problem
even between different Unix OS.
3) Purposely bind a socket to the server port:
If the binding succeeds, then the server is dead since port cannot be
re-used; otherwise if the binding fails and returns an error telling
port in used, then the server is alive. However, this approach faced
the similar problem as technique 1 if the port is re-used by other
process after server crashes and before we bind the socket.
4) Using "ps" command and pipe it to file:
Personaly I think this is the best and easiest solution. "ps" provides
comprehensive information such as execution filename, process ID,
process state of a process. In addition, almost every system has
similar command. The shortcomings are: overhead in using system() and
re-directing output from "ps" to file; slow file I/O operation (read).
"grep" can be used to filter out unnecessary processes information.
I am quite surprisied that nobody suggested this way. This is probably
due to ambiguity in my question asked.
Any comments are welcomed.
- Beng Hang Tay (email: taybengh at nusdiscs)
Dept. of Info. Sys. and Comp. Sc.
National University of Singapore