In C++, fork and kill not killing all the child processes

Question

I have below code which executes a binary in child process, wait for 1 sec and if it's not done then kill it.

     pid_t pid;
     pid=fork();
     if (pid == 0)
     {
         //In child
         execl("/bin/sh", "sh", "-c", "/opt/qcom/bin/version.out > /tmp/version", (char *)NULL);
         exit(0);
     }
     else
     {
         // In parent, wait for 1 second
         sleep(1);
         int status;
         if (waitpid(pid, &status, WNOHANG) != pid)
         {
             //kill(pid, SIGTERM); //--> tried this too
             kill(pid, SIGKILL);
         }
         fsmverDir("/tmp/version");
         system("rm /tmp/version");
     }

But it's not killing completely, I see below ps output after running my program 3 times (it created 3 version.out's), and "sh" appear as zombie...

# ps | grep "version.out\|sh"
2012 root         0 Z    [sh]
2013 root     13236 S    /opt/qcom/bin/version.out
2058 root         0 Z    [sh]
2059 root     13236 S    /opt/qcom/bin/version.out
2092 root         0 Z    [sh]
2093 root     13236 S    /opt/qcom/bin/version.out
2100 root      2360 S    grep version.out\|sh
# 

Or, is there a way to run the command with timeout in busybox Linux?
Something like:

execlp("timeout","timeout","1","sh","-c","/opt/qcom/bin/version.out > /tmp/version",NULL);

There is no timeout in my busybox version, is there an alternative?

Answer 1

You are creating a shell (the child) which in turn runs "version.out" (the grandchild).

You kill the child thereby making it a zombie and orphaning the grandchild. You can collect the child by calling wait a second time (it error-ed out the first time or you would never have called kill) but you still won't accomplish the goal of killing the grandchild from the parent.