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rdate.c 1.7 KB

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  1. /* vi: set sw=4 ts=4: */
  2. /*
  3. * The Rdate command will ask a time server for the RFC 868 time
  4. * and optionally set the system time.
  5. *
  6. * by Sterling Huxley <sterling@europa.com>
  7. *
  8. * Licensed under GPL v2 or later, see file License for details.
  9. */
  10. #include "libbb.h"
  11. enum { RFC_868_BIAS = 2208988800UL };
  12. static void socket_timeout(int sig UNUSED_PARAM)
  13. {
  14. bb_error_msg_and_die("timeout connecting to time server");
  15. }
  16. static time_t askremotedate(const char *host)
  17. {
  18. uint32_t nett;
  19. int fd;
  20. /* Add a timeout for dead or inaccessible servers */
  21. alarm(10);
  22. signal(SIGALRM, socket_timeout);
  23. fd = create_and_connect_stream_or_die(host, bb_lookup_port("time", "tcp", 37));
  24. if (safe_read(fd, (void *)&nett, 4) != 4) /* read time from server */
  25. bb_error_msg_and_die("%s did not send the complete time", host);
  26. close(fd);
  27. /* convert from network byte order to local byte order.
  28. * RFC 868 time is the number of seconds
  29. * since 00:00 (midnight) 1 January 1900 GMT
  30. * the RFC 868 time 2,208,988,800 corresponds to 00:00 1 Jan 1970 GMT
  31. * Subtract the RFC 868 time to get Linux epoch
  32. */
  33. return ntohl(nett) - RFC_868_BIAS;
  34. }
  35. int rdate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  36. int rdate_main(int argc UNUSED_PARAM, char **argv)
  37. {
  38. time_t remote_time;
  39. unsigned long flags;
  40. opt_complementary = "-1";
  41. flags = getopt32(argv, "sp");
  42. remote_time = askremotedate(argv[optind]);
  43. if ((flags & 2) == 0) {
  44. time_t current_time;
  45. time(&current_time);
  46. if (current_time == remote_time)
  47. bb_error_msg("current time matches remote time");
  48. else
  49. if (stime(&remote_time) < 0)
  50. bb_perror_msg_and_die("can't set time of day");
  51. }
  52. if ((flags & 1) == 0)
  53. printf("%s", ctime(&remote_time));
  54. return EXIT_SUCCESS;
  55. }