Monitoring and killing a process that runs too long

[Ksawery]

Dear all,

I have a very simple question: I run a process, and want to know how long it takes in order afterwards to be able to kill it if it runs too long.

I use the following code:

#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

void test(){

int pid = 0;
double lasttime=0;
 int status = 0;

 pid = fork();

if( pid == 0 ){
  system("echo HELLO");
  }
 else {
   int counter = 0;
   while (1)
     {
       counter++;
       if( counter > lasttime ) lasttime = counter;

       if (waitpid(pid, &status, 0) == pid) break;
     }
 }

 return;
}

so in principle 'lasttime' should be somehow the duration of my process. But it is always 0 when I print it out at the end...

I must be doing something wrong, but I don't see what.
Any remark would be welcome !

Cheers,
Xavier

[Peter87]

waitpid will not return until a state change happens in the child process. I think the only possible return value from waitpid is pid (except for errors) so the code inside the loop will never run more than once. This is a unix question so you probablt get better answers asking in UNIX/Linux Programming.