how know if process running

shifter · 06-16-2007, 06:13 AM

Hi all, I have a new programming question.
I am writing my personal daemon in C language.
How can I know if my program (daemon) is running?
( with C language, and not with shell )

For example, I try:

#./my program

Exist it a system call that I can use within myprogram to know if istance of myprogram is running?

Thank you in advance.

kstan · 06-16-2007, 06:37 AM

in shell, type this:-
ps aux

shifter · 06-16-2007, 06:45 AM

Quote:

in shell, type this:-
ps aux

No, I want it in C code!!
Have you read above post?

theNbomr · 06-16-2007, 12:13 PM

How about this:

Code:

   printf( "I'm running now\n" );

--- rod.

theNbomr · 06-16-2007, 12:17 PM

Oh, I think I get it now. You want to know whether a prior instance of the daemon was already running? Lock files are commonly used for this purpose. No matter what scheme you use, the tricky part is making sure the 'flag', of what ever sort you use, always gets cleared when the daemon exits. If it doesn't, any subsequent attempt to restart the process will fail.
--- rod.

shifter · 06-16-2007, 04:13 PM

For example, I can to set an exit code to 1 at first daemon instance, and when daemon exit, then I set exit code to 0.

theNbomr · 06-16-2007, 08:53 PM

In the your case, the mere presence of the entity is enough to indicate that an instance of the daemon already exists. The entity can be a file, a message queue, shared memory segment, or anything else that can be created and mutually located by arbitrary processes.
--- rod.

bigearsbilly · 06-18-2007, 03:37 AM

ho ho, now this is a question!

there is no definitive way to do it.
lock files are the simplest method and OK ish.

if it's a network server maybe you could have a method of poking it to see if it's alive.

the bottom line is these computer thingies still need us monkeys for some jobs.
when you solve this problem you will be helping them on the road to phasing us out