Checking if a process is alive or not.

In a multi-processing system - if we want to check if a given child process is alive or not (after forking it) for a longer period of time - we could send a signal 0 to the process using the kill API.

   #include <sys/types.h>
    #include <signal.h>

    int kill(pid_t pid, int sig);

Use this API to send a signal of 0. If the errno is set to ESRCH - then the process had most probably exited.