Re: Check if a process exists? (EXTENDING THE QUESTION)

["M.Baris Demiray" <baris@labristeknoloji.com>]

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lucianolnx wrote:
> Today, what are the bests ways to know if a deamon is running without 
> knowing its PID ? 

I'm not sure whether this is `the best way' but you can parse some proc
file system entry. Especially /proc/$pid/cmdline and /proc/$pid/status
will be useful. And you will have to search all the /proc/$pid entries
since you don't know the pid..

For example, they provide following information for clamd.

[baris@rhinox]$ ps aux|grep clamd
clamav     424  0.0  3.1  11520  7856 ?        Ss   01:35   0:03 
/usr/sbin/clamd
clamav    1184  0.0  3.1  11520  7856 ?        S    09:38   0:00 
/usr/sbin/clamd
baris     1238  0.0  0.2   1688   712 pts/2    S+   09:58   0:00 grep clamd
[baris@rhinox]$ cat /proc/1184/cmdline
/usr/sbin/clamd
[baris@rhinox]$ cat /proc/1184/status
Name:   clamd
State:  S (sleeping)
Tgid:   1184
Pid:    1184
PPid:   424
....
....

I also should add that /proc filesystem is _optional_ in configuration.
Highly likely it will exist on a target system but a little possibility
of being it unselected still there.

> My old technique (used until now), is based on recovering the PID saved by 
> the own process in a special and known location (like a file), almost all 
> times persisted (PERSISTENCE IS A PROBLEM). 
> 
> Luciano 

-- 
"You have to understand, most of these people are not ready to be
unplugged. And many of them are no inert, so hopelessly dependent
on the system, that they will fight to protect it."
                                                         Morpheus

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