286 lines
7.6 KiB
C
286 lines
7.6 KiB
C
/* $NetBSD: pom.c,v 1.14 2004/01/27 20:30:30 jsm Exp $ */
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/*
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* Copyright (c) 1989, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software posted to USENET.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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#ifndef lint
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__COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\
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The Regents of the University of California. All rights reserved.\n");
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#endif /* not lint */
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#ifndef lint
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#if 0
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static char sccsid[] = "@(#)pom.c 8.1 (Berkeley) 5/31/93";
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#else
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__RCSID("$NetBSD: pom.c,v 1.14 2004/01/27 20:30:30 jsm Exp $");
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#endif
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#endif /* not lint */
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/*
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* Phase of the Moon. Calculates the current phase of the moon.
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* Based on routines from `Practical Astronomy with Your Calculator',
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* by Duffett-Smith. Comments give the section from the book that
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* particular piece of code was adapted from.
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*
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* -- Keith E. Brandt VIII 1984
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*
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* Updated to the Third Edition of Duffett-Smith's book, Paul Janzen, IX 1998
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*
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*/
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#include <ctype.h>
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#include <err.h>
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#include <math.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <time.h>
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#include <unistd.h>
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#ifndef PI
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#define PI 3.14159265358979323846
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#endif
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/*
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* The EPOCH in the third edition of the book is 1990 Jan 0.0 TDT.
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* In this program, we do not bother to correct for the differences
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* between UTC (as shown by the UNIX clock) and TDT. (TDT = TAI + 32.184s;
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* TAI-UTC = 32s in Jan 1999.)
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*/
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#define EPOCH_MINUS_1970 (20 * 365 + 5 - 1) /* 20 years, 5 leaps, back 1 day to Jan 0 */
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#define EPSILONg 279.403303 /* solar ecliptic long at EPOCH */
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#define RHOg 282.768422 /* solar ecliptic long of perigee at EPOCH */
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#define ECCEN 0.016713 /* solar orbit eccentricity */
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#define lzero 318.351648 /* lunar mean long at EPOCH */
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#define Pzero 36.340410 /* lunar mean long of perigee at EPOCH */
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#define Nzero 318.510107 /* lunar mean long of node at EPOCH */
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void adj360(double *);
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double dtor(double);
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int main(int, char *[]);
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double potm(double);
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time_t parsetime(char *);
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void badformat(void) __attribute__((__noreturn__));
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int
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main(argc, argv)
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int argc;
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char *argv[];
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{
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time_t tmpt, now;
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double days, today, tomorrow;
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char buf[1024];
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/* Revoke setgid privileges */
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setregid(getgid(), getgid());
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if (time(&now) == (time_t)-1)
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err(1, "time");
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if (argc > 1) {
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tmpt = parsetime(argv[1]);
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strftime(buf, sizeof(buf), "%a %Y %b %e %H:%M:%S (%Z)",
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localtime(&tmpt));
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printf("%s: ", buf);
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} else {
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tmpt = now;
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}
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days = (tmpt - EPOCH_MINUS_1970 * 86400) / 86400.0;
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today = potm(days) + .5;
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if (tmpt < now)
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(void)printf("The Moon was ");
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else if (tmpt == now)
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(void)printf("The Moon is ");
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else
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(void)printf("The Moon will be ");
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if ((int)today == 100)
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(void)printf("Full\n");
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else if (!(int)today)
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(void)printf("New\n");
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else {
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tomorrow = potm(days + 1);
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if ((int)today == 50)
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(void)printf("%s\n", tomorrow > today ?
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"at the First Quarter" : "at the Last Quarter");
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/* today is 0.5 too big, but it doesn't matter here
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* since the phase is changing fast enough
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*/
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else {
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today -= 0.5; /* Now it might matter */
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(void)printf("%s ", tomorrow > today ?
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"Waxing" : "Waning");
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if (today > 50)
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(void)printf("Gibbous (%1.0f%% of Full)\n",
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today);
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else if (today < 50)
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(void)printf("Crescent (%1.0f%% of Full)\n",
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today);
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}
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}
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exit(0);
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}
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/*
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* potm --
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* return phase of the moon
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*/
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double
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potm(days)
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double days;
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{
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double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
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double A4, lprime, V, ldprime, D, Nm;
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N = 360 * days / 365.242191; /* sec 46 #3 */
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adj360(&N);
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Msol = N + EPSILONg - RHOg; /* sec 46 #4 */
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adj360(&Msol);
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Ec = 360 / PI * ECCEN * sin(dtor(Msol)); /* sec 46 #5 */
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LambdaSol = N + Ec + EPSILONg; /* sec 46 #6 */
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adj360(&LambdaSol);
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l = 13.1763966 * days + lzero; /* sec 65 #4 */
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adj360(&l);
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Mm = l - (0.1114041 * days) - Pzero; /* sec 65 #5 */
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adj360(&Mm);
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Nm = Nzero - (0.0529539 * days); /* sec 65 #6 */
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adj360(&Nm);
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Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 65 #7 */
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Ac = 0.1858 * sin(dtor(Msol)); /* sec 65 #8 */
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A3 = 0.37 * sin(dtor(Msol));
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Mmprime = Mm + Ev - Ac - A3; /* sec 65 #9 */
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Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 65 #10 */
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A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 65 #11 */
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lprime = l + Ev + Ec - Ac + A4; /* sec 65 #12 */
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V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 65 #13 */
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ldprime = lprime + V; /* sec 65 #14 */
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D = ldprime - LambdaSol; /* sec 67 #2 */
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return(50.0 * (1 - cos(dtor(D)))); /* sec 67 #3 */
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}
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/*
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* dtor --
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* convert degrees to radians
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*/
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double
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dtor(deg)
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double deg;
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{
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return(deg * PI / 180);
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}
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/*
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* adj360 --
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* adjust value so 0 <= deg <= 360
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*/
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void
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adj360(deg)
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double *deg;
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{
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for (;;)
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if (*deg < 0)
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*deg += 360;
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else if (*deg > 360)
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*deg -= 360;
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else
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break;
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}
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#define ATOI2(ar) ((ar)[0] - '0') * 10 + ((ar)[1] - '0'); (ar) += 2;
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time_t
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parsetime(p)
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char *p;
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{
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struct tm *lt;
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int bigyear;
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int yearset = 0;
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time_t tval;
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unsigned char *t;
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for (t = (unsigned char *)p; *t; ++t) {
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if (isdigit(*t))
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continue;
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badformat();
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}
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tval = time(NULL);
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lt = localtime(&tval);
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lt->tm_sec = 0;
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lt->tm_min = 0;
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switch (strlen(p)) {
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case 10: /* yyyy */
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bigyear = ATOI2(p);
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lt->tm_year = bigyear * 100 - 1900;
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yearset = 1;
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/* FALLTHROUGH */
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case 8: /* yy */
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if (yearset) {
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lt->tm_year += ATOI2(p);
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} else {
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lt->tm_year = ATOI2(p);
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if (lt->tm_year < 69) /* hack for 2000 */
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lt->tm_year += 100;
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}
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/* FALLTHROUGH */
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case 6: /* mm */
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lt->tm_mon = ATOI2(p);
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if ((lt->tm_mon > 12) || !lt->tm_mon)
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badformat();
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--lt->tm_mon; /* time struct is 0 - 11 */
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/* FALLTHROUGH */
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case 4: /* dd */
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lt->tm_mday = ATOI2(p);
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if ((lt->tm_mday > 31) || !lt->tm_mday)
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badformat();
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/* FALLTHROUGH */
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case 2: /* HH */
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lt->tm_hour = ATOI2(p);
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if (lt->tm_hour > 23)
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badformat();
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break;
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default:
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badformat();
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}
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/* The calling code needs a valid tm_ydays and this is the easiest
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* way to get one */
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if ((tval = mktime(lt)) == -1)
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errx(1, "specified date is outside allowed range");
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return (tval);
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}
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void
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badformat()
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{
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warnx("illegal time format");
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(void)fprintf(stderr, "usage: pom [[[[[cc]yy]mm]dd]HH]\n");
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exit(1);
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}
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