Implementing a custom command in a basic shell(in C) - linux

Question

I need to implement a custom command in a shell .The goal is to support a command program_name m that creates a child process to execute program_name, but aborts the process if it does not complete its operation in m seconds.
Actually I am checking the status of waitpid(child_pid,&exit_status,WUNTRACED) everytime ,but the code segment in the for loop is not working and is not aborting the process!!
Can anyone suggest me an appropriate routine from the library to deliver a SIGALRM signal after m seconds, and use a signal handler to perform appropriate actions?
Thanks in advance!!
int child_pid = fork();
if (child_pid < 0) {
perror("ERROR: could not fork process.\n");
}
if (child_pid == 0) {
char *args[4];
args[0] = path;
args[1] = "-c";
args[2] = command_line;
args[3] = (char *) 0;
//executing the command
int exec_return = execvp(path, args);
if (exec_return == -1) {
perror("error: command execution failed!\n");
} else {
exit(exec_return);
}
} else {
//assigning cur_fg_pid to the child
cur_fg_pid = child_pid + 1;
if (cur_fg_cmd == NULL) { cur_fg_cmd = (char *) malloc(sizeof(char)); }
strcpy(cur_fg_cmd, command_line);
int exit_status;
while (can_wait == 1 && waitpid(child_pid, &exit_status, 0) > 0) {}
cur_fg_pid = -1;
cur_fg_cmd = NULL;
if (can_wait == 1) latest_jobid = -1;
if(global_time_flag)
{
for (i = 0; i < stip_time; i++) {
if (waitpid(child_pid,&exit_status,WUNTRACED) > 0)
if (WIFSTOPPED(exit_status)) {
break;
} else {sleep(1);}
}
if(!WIFSTOPPED(exit_status ))
kill (child_pid, SIGUSR1);
}
}