I am trying to write subshell in linux with c. I am compiling it in normal linux terminal and run it like ./shell. However, I have trouble about Ctrl-Z and Ctrl-C. When I press the Ctrl-Z for example, it stops ./myshell, but I want to stop process which is in the myshell.
I am setting new process group after the for like:
int pid = fork();
if (!setpgid(pid, 0)) {
} else {
perror("PGID Error: ");
return(-1);
}
After I check is there any & sign for background process I understand it is foreground process then I put new process into foreground then I am waiting the finish or stop of process with waitpid. Then I put terminal into foreground. In there I am using sigprocmask for SIGTTOU, otherwise when I try to put my shell again into foreground it stops backs to linux shell.
tcsetpgrp(1,getpgid(pid));
waitpid(pid, NULL, 0);
if (sigprocmask(SIG_BLOCK, &intmask, NULL) == -1)
perror("sigprocmask error: ");
tcsetpgrp(1, shellpid);
kill(shellpid, SIGCONT);
if (sigprocmask(SIG_UNBLOCK, &intmask, NULL) == -1)
perror("sigprocmask error: ");
I have also signal handlers to avoid my_shell to terminate or stop. I am planning the stop or terminate just foreground processes with Control-Z and Control-C.
void handler_sigint(int signum)
{
pid_t foregroundpgid=tcgetpgrp(0);
if(foregroundpgid!=shellpid) {
kill(foregroundpgid, SIGINT);
}
}
void handler_sigtstp(int sig)
{
pid_t foregroundpgid=tcgetpgrp(0);
if(foregroundpgid!=shellpid) {
kill(foregroundpgid, SIGSTOP);
}
}
Control-C works very well but I have trouble with Control-Z. For example I start cat in my shell when I press Control-Z it just writes ^Z in the terminal does not stop foreground process. Please look at the picture