I created a program that takes a list of arguments and put them in a grid on a new tty where I can move around and select from it what I want.
When I run the program without backticks like this...
$> ./ft_select arg_1 arg_2 ... arg_N
A new tty is opened and a grid is shown...
arg_1 arg_2 arg_3
arg_4 arg_5 arg_6
arg_7 ... arg_N
I hit ctrl+z and the program gets suspended with no problem and fg command puts it back.
My problem is that when I put the command between backticks and I try to suspend it, it get stuck without giving the prompt back.
I have to mention that I write all the content of the grid on /dev/tty
You can find in the code below the function that does the signal handling.
23 void signalhandler(int sig)
24 {
25 // struct winsize ws;
26
27 if (sig == SIGWINCH)
28 {
29 // ioctl(g_data->tty, TIOCGWINSZ, &ws);
30 update_data(g_data);
31 print_args(g_data);
32 update_cursor(g_data, 1);
33 }
34 else if (sig == SIGTSTP)
35 {
36 signal(SIGTSTP, SIG_DFL);
37 enable_cap("te");
38 modify_main_caps(SET, g_data->tty);
39 ioctl(g_data->tty, TIOCSTI, "\032");
40 }
41 else if (sig == SIGCONT)
42 {
43 signal(SIGTSTP, signalhandler);
44 modify_main_caps(UNSET, g_data->tty);
45 update_data(g_data);
46 print_args(g_data);
47 update_cursor(g_data, 1);
48 }
49 else if (sig == SIGINT)
50 {
51 enable_cap("te");
52 modify_main_caps(SET, g_data->tty);
53 exit(EXIT_FAILURE);
54 }
55 }
CTRL+Z causes the terminal device driver to send a SIGTSTP to all processes in the foreground process group. In bash and zsh, at least, commands in a command substitution $(<command>) are executed in a subshell, but they don't get their own process group (they run in the same process group as the parent shell itself). That means that CTRL+Z should not affect them at all - press it and nothing happens, just like pressing CTRL+Z in a shell prompt doesn't do anything: in both cases, there is no foreground process group to suspend!