12.31

/*
 * 12.31.c
 */
#include <stdio.h>
#include "csapp.h"

sigjmp_buf buf;

void sigchild_handler(int sig) {
  siglongjmp(buf, 1);
}

char *tfgets(char *s, int size, FILE *stream) {
  if (Fork() == 0) {
    Sleep(5);
    exit(0);
  }

  switch (sigsetjmp(buf, 1)) {
    case 0:
      Signal(SIGCHLD, sigchild_handler);
      return fgets(s, size, stream);
    case 1:
      return NULL;
  }
}

int main(int argc, char* argv[]) {
  char buf[MAXLINE];

  if (tfgets(buf, MAXLINE, stdin) == NULL)
    printf("BOOM!\n");
  else
    printf("%s", buf);

  return 0;
}