How to get back to shell after SIGTSTP - c++

Question

I am writing on a UNIX shell.
When CTRL-C is pressed, the SIGINT signal is sent. (Is working!)
But when CTRL-Z is pressed, the process which gets the signal is stopped, but I cannot return to my shell. Only if I close the process, i can return.
Here is my signal_handler():
// in the main()
signal(SIGINT, signal_handler);
signal(SIGTSTP, signal_handler);
// when pid == 0, right over execvp()
signal(SIGINT, SIG_DFL);
signal(SIGTSTP, SIG_DFL);
// signal handler
void signal_handler(int signum) {
switch(signum) {
case SIGINT:
cout << "[caught SIGINT]" << endl;
kill(pid, SIGINT);
break;
case SIGTSTP:
cout << "[caught SIGTSTP]" << endl;
kill(pid, SIGTSTP);
break;
default:
break;
}
}
pid_t pid; // is a global variable
// this would be my main()
if((pid = fork()) < 0) {
cout << "Error" << endl;
exit(1);
} else if(pid == 0) { // child
setpgid(0,0);
signal(SIGINT, SIG_DFL);
signal(SIGTSTP, SIG_DFL);
execvp(arguments[0], &arguments[0]);
cout << "Argument not found" << endl;
exit(1);
} else if(checkIfBackground(inputNew) == false) { // mother
int status;
pid_t pid_r;
if(waitpid(pid, &status, 0) < 0) {
cout << "Error" << endl;
}
} else {
cout << "Process is in background" << endl;
}

Answer 1

You'll need to check the status of your children to see when they've stopped with the UNTRACED flag:
pid_t child = waitpid(-1, &status, WUNTRACED | WCONTINUED);
if (WIFSTOPPED(status))
... the child has stopped
else if (WIFCONTINUED(status))
... the child has been continued
else if (WIFEXITED(status))
... the child has exited with exit
else if (WIFSIGNALLED(status))
... the child exited with a signal
Note that if you don't care about switches to running status (the WIFCONTINUED case), you don't need the WCONTINUED flag.