Useful UNIX Programs

by Marshall Plann

This program lets you see what any word will look like after it's run through crypt().  This is particularly useful for the next program.

word.c:

#include <pwd.h>
main(argc, argv)
int argc;
char *argv[];
{
  if (argc > 2)
    printf("%s\n", crypt(argv[1], argv[2]));
  else if (argc > 1)
    printf("%s\n", crypt(argv[1], "hi"));
}

This program will allow you to lock up any terminal on a UNIX system until the secret word is entered.  In this case, the secret word is: dog

The word is listed in encrypted form, otherwise anyone listing your program would be able to see it.

secret.c:

/* Save this as 'secret.c' and type 'cc secret.c -o secret' to compile. */

#include <stdio.h>
#include <sys/ioctl.h>
#include <signal.h>
#include <pwd.h>

main(argc, argv)
int argc;
char **argv;
{
  struct sgttyb basic;
  short flags;
  char str[32];
  int i;

/* Ignore all interrupts that may try to mess up this program like ^C, ^Z */
  for (i = 1; i < 33; signal(i++, SIG_IGN));

/* Shut off echo and receive key strokes as they are hit from the terminal */

  ioctl(fileno(stdin), TIOCGETP, &basic);
  flags = basic.sg_flags;
  basic.sg_flags |= CBREAK;
  basic.sg_flags &= ~ECHO;
  ioctl(fileno(stdin), TIOCSETP, &basic);

  do {
    /* Prompt for the input */
    fprintf(stdout, "Enter Secret Word> "), fflush(stdout);

    /* Get the input until a return or a lot of keys are hit */
    for (i = 0; (i < 31) && ((str[i] = getchar()) != '\n'); i++);
    /* Terminate the string */
    str[i] = '\0';

    /* Acknowledge that you have accepted the return by echoing it */

    fprintf(stdout, "\n");

     /* Repeat until the word has been entered */
  }
  while (strcmp(crypt(str, "hi"), "higSfxQjrCp7Y"));

/* Restore the terminal back to the original settings */
  basic.sg_flags = flags;
  ioctl(fileno(stdin), TIOCSETP, &basic);

/* Do something with the secret string here, I just print it out...
   You could have fun with it */
  fprintf(stdout, "->%s\n", str);
  fflush(stdout);
}

Code: word.c

Code: secret.c
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