commands/cal/cal.c

   1 /* cal - print a calendar               Author: Maritn Minow */
   2
   3 #include <stdlib.h>
   4 #include <string.h>
   5 #include <stdio.h>
   6
   7 #define do3months       domonth
   8 #define IO_SUCCESS      0       /* Unix definitions              */
   9 #define IO_ERROR        1
  10 #define EOS     0
  11
  12 #define ENTRY_SIZE      3       /* 3 bytes per value             */
  13 #define DAYS_PER_WEEK   7       /* Sunday, etc.                  */
  14 #define WEEKS_PER_MONTH 6       /* Max. weeks in a month         */
  15 #define MONTHS_PER_LINE 3       /* Three months across           */
  16 #define MONTH_SPACE     3       /* Between each month            */
  17
  18 char *badarg = {"Bad argument\n"};
  19 char *how = {"Usage: cal [month] year\n"};
  20
  21 /* Calendar() stuffs data into layout[],
  22  * output() copies from layout[] to outline[], (then trims blanks).
  23  */
  24 char layout[MONTHS_PER_LINE][WEEKS_PER_MONTH][DAYS_PER_WEEK][ENTRY_SIZE];
  25 char outline[(MONTHS_PER_LINE * DAYS_PER_WEEK * ENTRY_SIZE)
  26        + (MONTHS_PER_LINE * MONTH_SPACE)
  27        + 1];
  28
  29 char *weekday = " S  M Tu  W Th  F  S";
  30 char *monthname[] = {
  31              "???",             /* No month 0    */
  32              "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  33              "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  34 };
  35
  36 int main(int argc, char **argv);
  37 void doyear(int year);
  38 void domonth(int year, int month);
  39 void output(int nmonths);
  40 void calendar(int year, int month, int indx);
  41 void usage(char *s);
  42 int date(int year, int month, int week, int wday);
  43 void setmonth(int year, int month);
  44 int getdate(int week, int wday);
  45 static int Jan1(int year);
  46
  47 int main(argc, argv)
  48 int argc;
  49 char *argv[];
  50 {
  51   register int year;
  52
  53   register int arg1val;
  54   int arg1len;
  55   int arg2val;
  56
  57   if (argc <= 1) {
  58         usage(how);
  59   } else {
  60         arg1val = atoi(argv[1]);
  61         arg1len = strlen(argv[1]);
  62         if (argc == 2) {
  63                 /* Only one argument, if small, it's a month.  If
  64                  * large, it's a year.  Note: cal               0082    Year
  65                  * 0082 cal             82      Year 0082 */
  66                 if (arg1len <= 2 && arg1val <= 12)
  67                         do3months(year, arg1val);
  68                 else
  69                         doyear(arg1val);
  70         } else {
  71                 /* Two arguments, allow 1980 12 or 12 1980 */
  72                 arg2val = atoi(argv[2]);
  73                 if (arg1len > 2)
  74                         do3months(arg1val, arg2val);
  75                 else
  76                         do3months(arg2val, arg1val);
  77         }
  78   }
  79   return(IO_SUCCESS);
  80 }
  81
  82 void doyear(year)
  83 int year;
  84 /* Print the calendar for an entire year. */
  85 {
  86   register int month;
  87
  88   if (year < 1 || year > 9999) usage(badarg);
  89   if (year < 100)
  90         printf("\n\n\n                                 00%2d\n\n", year);
  91   else
  92         printf("\n\n\n%35d\n\n", year);
  93   for (month = 1; month <= 12; month += MONTHS_PER_LINE) {
  94         printf("%12s%23s%23s\n",
  95                monthname[month],
  96                monthname[month + 1],
  97                monthname[month + 2]);
  98         printf("%s   %s   %s\n", weekday, weekday, weekday);
  99         calendar(year, month + 0, 0);
 100         calendar(year, month + 1, 1);
 101         calendar(year, month + 2, 2);
 102         output(3);
 103 #if MONTHS_PER_LINE != 3
 104 #error  "the above will not work"
 105 #endif
 106   }
 107   printf("\n\n\n");
 108 }
 109
 110 void domonth(year, month)
 111 int year;
 112 int month;
 113 /* Do one specific month -- note: no longer used */
 114 {
 115   if (year < 1 || year > 9999) usage(badarg);
 116   if (month <= 0 || month > 12) usage(badarg);
 117   printf("%9s%5d\n\n%s\n", monthname[month], year, weekday);
 118   calendar(year, month, 0);
 119   output(1);
 120   printf("\n\n");
 121 }
 122
 123 void output(nmonths)
 124 int nmonths;                    /* Number of months to do        */
 125 /* Clean up and output the text. */
 126 {
 127   register int week;
 128   register int month;
 129   register char *outp;
 130   int i;
 131   char tmpbuf[21], *p;
 132
 133   for (week = 0; week < WEEKS_PER_MONTH; week++) {
 134         outp = outline;
 135         for (month = 0; month < nmonths; month++) {
 136                 /* The -1 in the following removes the unwanted
 137                  * leading blank from the entry for Sunday. */
 138                 p = &layout[month][week][0][1];
 139                 for (i = 0; i < 20; i++) tmpbuf[i] = *p++;
 140                 tmpbuf[20] = 0;
 141                 sprintf(outp, "%s   ", tmpbuf);
 142                 outp += (DAYS_PER_WEEK * ENTRY_SIZE) + MONTH_SPACE - 1;
 143         }
 144         while (outp > outline && outp[-1] == ' ') outp--;
 145         *outp = EOS;
 146         printf("%s\n", outline);
 147   }
 148 }
 149
 150 void calendar(year, month, indx)
 151 int year;
 152 int month;
 153 int indx;                       /* Which of the three months             */
 154 /* Actually build the calendar for this month. */
 155 {
 156   register char *tp;
 157   int week;
 158   register int wday;
 159   register int today;
 160
 161   setmonth(year, month);
 162   for (week = 0; week < WEEKS_PER_MONTH; week++) {
 163         for (wday = 0; wday < DAYS_PER_WEEK; wday++) {
 164                 tp = &layout[indx][week][wday][0];
 165                 *tp++ = ' ';
 166                 today = getdate(week, wday);
 167                 if (today <= 0) {
 168                         *tp++ = ' ';
 169                         *tp++ = ' ';
 170                 } else if (today < 10) {
 171                         *tp++ = ' ';
 172                         *tp = (today + '0');
 173                 } else {
 174                         *tp++ = (today / 10) + '0';
 175                         *tp = (today % 10) + '0';
 176                 }
 177         }
 178   }
 179 }
 180
 181 void usage(s)
 182 char *s;
 183 {
 184 /* Fatal parameter error. */
 185
 186   fprintf(stderr, "%s", s);
 187   exit(IO_ERROR);
 188 }
 189
 190 /* Calendar routines, intended for eventual porting to TeX
 191  *
 192  * date(year, month, week, wday)
 193  *      Returns the date on this week (0 is first, 5 last possible)
 194  *      and day of the week (Sunday == 0)
 195  *      Note: January is month 1.
 196  *
 197  * setmonth(year, month)
 198  *      Parameters are as above, sets getdate() for this month.
 199  *
 200  * int
 201  * getdate(week, wday)
 202  *      Parameters are as above, uses the data set by setmonth()
 203  */
 204
 205 /* This structure is used to pass data between setmonth() and getdate().
 206  * It needs considerable expansion if the Julian->Gregorian change is
 207  * to be extended to other countries.
 208  */
 209
 210 static struct {
 211   int this_month;               /* month number used in 1752 checking    */
 212   int feb;                      /* Days in February for this month       */
 213   int sept;                     /* Days in September for this month      */
 214   int days_in_month;            /* Number of days in this month          */
 215   int dow_first;                /* Day of week of the 1st day in month   */
 216 } info;
 217
 218 static int day_month[] = {      /* 30 days hath September...             */
 219                   0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
 220 };
 221
 222 int date(year, month, week, wday)
 223 int year;                       /* Calendar date being computed          */
 224 int month;                      /* January == 1                          */
 225 int week;                       /* Week in the month 0..5 inclusive      */
 226 int wday;                       /* Weekday, Sunday == 0                  */
 227 /* Return the date of the month that fell on this week and weekday.
 228  * Return zero if it's out of range.
 229  */
 230 {
 231   setmonth(year, month);
 232   return(getdate(week, wday));
 233 }
 234
 235 void setmonth(year, month)
 236 int year;                       /* Year to compute               */
 237 int month;                      /* Month, January is month 1     */
 238 /* Setup the parameters needed to compute this month
 239  * (stored in the info structure).
 240  */
 241 {
 242   register int i;
 243
 244   if (month < 1 || month > 12) {/* Verify caller's parameters    */
 245         info.days_in_month = 0; /* Garbage flag                  */
 246         return;
 247   }
 248   info.this_month = month;      /* used in 1752 checking         */
 249   info.dow_first = Jan1(year);  /* Day of January 1st for now    */
 250   info.feb = 29;                /* Assume leap year              */
 251   info.sept = 30;               /* Assume normal year            */
 252   /* Determine whether it's an ordinary year, a leap year or the
 253    * magical calendar switch year of 1752. */
 254   switch ((Jan1(year + 1) + 7 - info.dow_first) % 7) {
 255       case 1:                   /* Not a leap year               */
 256         info.feb = 28;
 257       case 2:                   /* Ordinary leap year            */
 258         break;
 259
 260       default:                  /* The magical moment arrives    */
 261         info.sept = 19;         /* 19 days hath September        */
 262         break;
 263   }
 264   info.days_in_month =
 265         (month == 2) ? info.feb
 266         : (month == 9) ? info.sept
 267         : day_month[month];
 268   for (i = 1; i < month; i++) {
 269         switch (i) {            /* Special months?               */
 270             case 2:             /* February                      */
 271                 info.dow_first += info.feb;
 272                 break;
 273
 274             case 9:     info.dow_first += info.sept;    break;
 275
 276             default:
 277                 info.dow_first += day_month[i];
 278                 break;
 279         }
 280   }
 281   info.dow_first %= 7;          /* Now it's Sunday to Saturday   */
 282 }
 283
 284 int getdate(week, wday)
 285 int week;
 286 int wday;
 287 {
 288   register int today;
 289
 290   /* Get a first guess at today's date and make sure it's in range. */
 291   today = (week * 7) + wday - info.dow_first + 1;
 292   if (today <= 0 || today > info.days_in_month)
 293         return(0);
 294   else if (info.sept == 19 && info.this_month == 9
 295          && today >= 3)         /* The magical month?    */
 296         return(today + 11);     /* If so, some dates changed     */
 297   else                          /* Otherwise,                    */
 298         return(today);          /* Return the date               */
 299 }
 300
 301 static int Jan1(year)
 302 int year;
 303 /* Return day of the week for Jan 1 of the specified year. */
 304 {
 305   register int day;
 306
 307   day = year + 4 + ((year + 3) / 4);    /* Julian Calendar       */
 308   if (year > 1800) {            /* If it's recent, do    */
 309         day -= ((year - 1701) / 100);   /* Clavian correction    */
 310         day += ((year - 1601) / 400);   /* Gregorian correction  */
 311   }
 312   if (year > 1752)              /* Adjust for Gregorian  */
 313         day += 3;               /* calendar              */
 314   return(day % 7);
 315 }