Check if a process exists?

Check if a process exists?

[Hareesh Nagarajan]

Hi,

Can a process check if a given PID exists or not? In other words can a
process check if an unrelated process is alive? Is there any system
call that does this?

I can think of a (few) work arounds to this:

1. open("/proc/pid_in_question") will return true if the process with
pid = pid_in_question is alive.

2. lock a file called ``pid_in_question". Test the lock from the other
process.  If the process is dead then there is no lock on the file
``pid_in_question".

Any ideas/comments?

Thanks,

Hareesh

Re: Check if a process exists?

[Holger Kiehl]

On Tue, 1 Mar 2005, Hareesh Nagarajan wrote:

> Hi,
>
> Can a process check if a given PID exists or not? In other words can a
> process check if an unrelated process is alive? Is there any system
> call that does this?
>
Use kill() with a second argument being zero.

     if (kill(pid, 0) == -1)
     {
        /* Process is not there. */
     }
     else
     {
        /* Process is alive. */
     }

Holger