Catching SIGINT signal to terminate a custom shell

Question

Hope you can help me to resolve this problem.

For school I have to transform Ctrl+C to a command which doesn\'t shut down the shell, but he reminds through

Answer 1

Here's a trivial implementation of handling SIGINT using sigaction which will work on posix systems. Left out error checking for brevity. The linked manual should explain about sigaction.

Basically the program loops through an infinite loop and break if user types exit. Using write as you can't use printf in signal handler. See signal manual for a list of functions that can be used safely in a signal handler.

#include
#include
#include
#include

char s[]="Type 'exit' to terminate\n";

void int_handler (int signum)
{
  write(fileno(stdin), s, sizeof s - 1);
}

int main (void)
{
  char str[256];
  struct sigaction sh;

  sh.sa_handler = int_handler;
  sigemptyset (&sh.sa_mask);
  sh.sa_flags = 0;
  sigaction (SIGINT, &sh, NULL);
  printf("%s", s);

  while(1) {
    fgets(str, sizeof str, stdin);
    char *p = strchr(str, '\n');
    if(p) *p = 0;
    if(!strcmp(str, "exit")) {
      printf("Exiting on request...");
      break;
    }
  }
  return 0;
}