Usenet 1994 January/usenetsourcesnewsgroupsinfomagicjanuary1994.iso/sources/misc/volume3/utc

Text File | 1989-02-03 | 3.4 KB | 123 lines

Path: xanth!mcnc!rutgers!ucsd!ames!necntc!ncoast!allbery
From: [e-mail] (BALDWIN)
Newsgroups: comp.sources.misc
Subject: v03i079: N.B.S. Time Service program
Summary: I've got (a small) one
Keywords: naval observatory
Message-ID: <[e-mail]>
Date: 12 Jul 88 14:48:27 GMT
Sender: [e-mail]
Reply-To: [e-mail] (BALDWIN)
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 107
Approved: [e-mail]

Posting-number: Volume 3, Issue 79
Submitted-by: "BALDWIN" <[e-mail]>
Archive-name: utc

I've been running such a program, which I wrote, at home for over six
months now.  It's written in C, and runs under System V (or any UNIX
system with an stime(2) system call).  It consists of a single program
called "utc" (universal time coordinated).  When invoked with options,
it reads the Naval clock and does one or both of these things:

    -s    sets the time via stime(2)
    -p    prints the time via ctime(3C)

If it can't read the time from the standard input, it exits non-zero.
When invoked without options, it prints the time in Naval clock format
for about a minute.  Thus, it can be installed as a login shell to provide
time service for your other systems without having them all call DC.
As a test, "utc | utc -p" should print the current time.  You can pipe
cu right into it, so set up a crontab entry to execute

    cu 1-201-653-0351 | utc -s

You may have to fix your cu to die properly when it receives a SIGPIPE.
I have my crontab entry run once a day, but it only calls DC if the
time hasn't been set in over a week.  A simple shell file accomplishes
this:

    LAST=/etc/.lastutc
    [ -z "`find $LAST -mtime -7 -print`" ] &&
    cu 1-202-653-0351 | utc -s && >$LAST

---8<--------8<---------- cut here for utc.c ------------8<--------------8<---
echo x - utc.c
sed 's/^X//' << \EOF > utc.c
X/*
X * The Naval Observatory clock ([phone]) prints this every second:
X *
X *    *
X *    jjjjj ddd hhmmss UTC
X *
X * jjjjj    Julian date modulo 2400000
X * ddd        days since beginning of year
X * hhmmss    time of day in Universal Time Coordinated
X */
X
X#include <stdio.h>
X#include <time.h>
X#include <sys/types.h>
X
X#define    EPOCH        40587            /* UNIX starts JD 2440587, */
X#define    leap(y, m)    ((y+m-1 - 70%m) / m)    /* also known as 1/1/70 */
X#define    TONE        '*'
X#define    TIME        "\n%05ld %03d %02d%02d%02d UTC"
X
Xmain(argc, argv)
Xint    argc;
Xchar    *argv[];
X{
X    int    setflg = 0, prtflg = 0;
X    int    y, d, h, m, s;
X    long    j;
X    time_t    now;
X    int    c;
X
X    while ((c = getopt(argc, argv, "sp")) != EOF)
X        switch (c) {
X        case 's': setflg++; break;
X        case 'p': prtflg++; break;
X        default:
X            fprintf(stderr, "usage: %s [-s] [-p]\n", argv[0]);
X            return 1;
X        }
X    if (setflg || prtflg) {
X        while ((c = getchar()) != TONE)
X            if (c == EOF)
X                return 1;
X        if (scanf(TIME, &j, &d, &h, &m, &s) != 5)
X            return 1;
X        now = (((j - EPOCH) * 24 + h) * 60 + m) * 60 + s;
X        if (setflg && stime(&now) == -1)
X            perror(argv[0]);
X        if (prtflg)
X            fputs(ctime(&now), stdout);
X    } else {
X        for (c = 0; c < 60; c++) {
X            time(&now);
X            s = (now % 60);
X            m = (now /= 60) % 60;
X            h = (now /= 60) % 24;
X            d = (now /= 24) % 365;
X            j = now + EPOCH;
X            y = (now /= 365);
X            d += 1 - leap(y, 4) + leap(y, 100) - leap(y, 400);
X            putchar(TONE);
X            printf(TIME, j, d, h, m, s);
X            putchar('\n');
X            fflush(stdout);
X            sleep(1);
X        }
X    }
X    return 0;
X}
EOF
exit 0
--
Michael Scott Baldwin        research!mike    attmail!mike    [e-mail]
AT&T Bell Laboratories        [phone]