ast_comparator/test/student_data/handout/shlab-handout/cases/31_tsh.c
/*
 * 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)
{
  int pid = fgpid(jobs);
  if(pid != 0){
	printf("stop");
	getjobpid(jobs, pid)->state = ST;
	kill(-pid, SIGTSTP);
  }
  return;
}
void sigtstp_handler ( int sig ) { int pid = fgpid ( jobs ) ; if ( pid != 0 ) { printf ( " " ) ; getjobpid ( jobs , pid ) -> state = ST ; 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 .
//if there is a foreprocess, we should stop it and also change the state
