1 /* vi: set sw=4 ts=4: */
3 * The Rdate command will ask a time server for the RFC 868 time
4 * and optionally set the system time.
6 * by Sterling Huxley <sterling@europa.com>
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
25 #include <sys/types.h>
26 #include <sys/socket.h>
27 #include <netinet/in.h>
38 static const int RFC_868_BIAS = 2208988800UL;
40 static time_t askremotedate(const char *host)
43 struct sockaddr_in s_in;
44 struct servent *tserv;
45 unsigned long int nett, localt;
48 if (!(h = gethostbyname(host))) /* get the IP addr */
49 perror_msg_and_die("%s", host);
51 if ((tserv = getservbyname("time", "tcp")) == NULL) /* find port # */
52 perror_msg_and_die("%s", "time");
54 if ((fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) /* get net connection */
55 perror_msg_and_die("%s", "socket");
57 memcpy(&s_in.sin_addr, h->h_addr, sizeof(s_in.sin_addr));
58 s_in.sin_port= tserv->s_port;
59 s_in.sin_family = AF_INET;
61 if (connect(fd, (struct sockaddr *)&s_in, sizeof(s_in)) < 0) /* connect to time server */
62 perror_msg_and_die("%s", host);
64 if (read(fd, (void *)&nett, 4) != 4) /* read time from server */
65 error_msg_and_die("%s did not send the complete time", host);
69 /* convert from network byte order to local byte order.
70 * RFC 868 time is the number of seconds
71 * since 00:00 (midnight) 1 January 1900 GMT
72 * the RFC 868 time 2,208,988,800 corresponds to 00:00 1 Jan 1970 GMT
73 * Subtract the RFC 868 time to get Linux epoch
75 localt= ntohl(nett) - RFC_868_BIAS;
80 int rdate_main(int argc, char **argv)
87 /* Interpret command line args */
88 /* do special-case option parsing */
89 if (argv[1] && (strcmp(argv[1], "--help") == 0))
92 /* do normal option parsing */
93 while ((opt = getopt(argc, argv, "Hsp")) > 0) {
108 /* the default action is to set the date */
109 if (printdate==0 && setdate==0) setdate++;
114 remote_time = askremotedate(argv[optind]);
117 if (stime(&remote_time) < 0)
118 perror_msg_and_die("Could not set time of day");
122 printf("%s", ctime(&remote_time));