Hi All I am new to unix programming. I have a
problem, I am using fork and in the child
process I am doing some what like this,

if ((pid = fork()) == 0) {
execvp(path, regdArgv);/*execute "my executable"*/
}

which will invoke an executable. But i just
want to do some thing like this,
if ((pid = fork()) == 0) {
if (/my executable is already running*/){
exit(0);
}
else{
execvp(path, regdArgv);
}

}

Can some body explain how to CHECK that executable
is already running ?

Thanks in Advance,
Seema Rao

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On 2005-10-29, seema_coma@yahoo.co.in <seema_coma@yahoo.co.in> wrote:
> Hi All I am new to unix programming. I have a
> problem, I am using fork and in the child
> process I am doing some what like this,
>
> if ((pid = fork()) == 0) {
> execvp(path, regdArgv);/*execute "my executable"*/
>}
>
> which will invoke an executable. But i just
> want to do some thing like this,
> if ((pid = fork()) == 0) {
>     if (/my executable is already running*/){
>          exit(0);
>     }
>     else{
>         execvp(path, regdArgv);
>     }
>
>}
>
> Can some body explain how to CHECK that executable
> is already running ?
>
> Thanks in Advance,
> Seema Rao
>

Well, other than the obvious question of why you want to do this
[what if someone wants to run multiple instances of the program],
i'd suggest using a pidfile

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I just want to stop running multiple instance of the program.Would you
please give me a hint on how to use pidfile

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On 2005-10-29, seema_coma@yahoo.co.in <seema_coma@yahoo.co.in> wrote:
> I just want to stop running multiple instance of the program.Would you
> please give me a hint on how to use pidfile

Can you explain _why_ you want that?

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Basically my executable again forks and executes a system wide daemon.
So if i run multiple instance of the code i am mentioning like,
linux_i32/somepad&;linux_i32/somepad&;linux_i32/somepad&
It will invoke multiple instances of daemon and even my Linux Box goes
out of memory and hangs. Thats why!!

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 2005 11:57:23 GMT)
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On 2005-10-29, seema_coma@yahoo.co.in <seema_coma@yahoo.co.in> wrote:
> Basically my executable again forks and executes a system wide daemon.
> So if i run multiple instance of the code i am mentioning like,
> linux_i32/somepad&;linux_i32/somepad&;linux_i32/somepad&
> It will invoke multiple instances of daemon and even my Linux Box goes
> out of memory and hangs. Thats why!!

This should be handled from the initscript [shell script in
/etc/init.d or /etc/rc.d] that invokes your system daemon - not in a
binary executable.

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We use this Daemon as System Daemon and some time Daemon for single
user. So how do I stop multiple instance in that case?

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On 2005-10-29, seema_coma@yahoo.co.in <seema_coma@yahoo.co.in> wrote:
> We use this Daemon as System Daemon and some time Daemon for single
> user. So how do I stop multiple instance in that case?

Redesign your program - what kind of daemon is it?

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seema_coma@yahoo.co.in writes:

> Hi All I am new to unix programming. I have a
> problem, I am using fork and in the child
> process I am doing some what like this,
>
> if ((pid = fork()) == 0) {
> execvp(path, regdArgv);/*execute "my executable"*/
> }
>
> which will invoke an executable. But i just
> want to do some thing like this,
> if ((pid = fork()) == 0) {
>     if (/my executable is already running*/){
>          exit(0);
>     }
>     else{
>         execvp(path, regdArgv);
>     }
>
> }
>
> Can some body explain how to CHECK that executable
> is already running ?

Have the executable create a file somewhere (on a *local* file
system), and get a lock on it. It can simply be a zero length file,
the important thing is that it's locked.

When the program starts up, have it try to get a lock on the file. If
it can't get a lock, then an instance of the program is already
running.

Joe
--
Gort, klatu barada nikto

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