ast_comparator/test/student_data/handout/shlab-handout/cases/reference_8_tsh.c
void sigtstp_handler(int sig)
{

    pid_t pid = fgpid(jobs);

    if(pid!=0 ){
    kill(-pid, SIGTSTP);
    }
    //already stop the job, don’t do it again
    return;
}
/*
 * sigtstp_handler - The kernel sends a SIGTSTP to the shell whenever
 *     the user types ctrl-z at the keyboard. Catch it and suspend the
 *     foreground job by sending it a SIGTSTP.
 */
The kernel sends a SIGTSTP to the shell whenever
the user types ctrl-z at the keyboard. Catch it and suspend the
foreground job by sending it a SIGTSTP.
The kernel sends a SIGTSTP to the shell whenever the user types ctrl - z at the keyboard . Catch it and suspend the foreground job by sending it a SIGTSTP .
void sigtstp_handler(int sig)
{
    pid_t pid = fgpid(jobs);
    if(pid!=0 ){
    kill(-pid, SIGTSTP);
    }
    return;
}
void sigtstp_handler ( int sig ) { pid_t pid = fgpid ( jobs ) ; if ( pid != 0 ) { kill ( - pid , SIGTSTP ) ; } return ; }
sigtstp_handler - The kernel sends a SIGTSTP to the shell whenever
     the user types ctrl-z at the keyboard.
sigtstp_handler - The kernel sends a SIGTSTP to the shell whenever the user types ctrl - z at the keyboard .
//already stop the job, don’t do it again