xref: /third_party/toybox/toys/posix/cal.c (revision 0f66f451) 
1/* cal.c - show calendar.
2 *
3 * Copyright 2011 Rob Landley <rob@landley.net>
4 *
5 * See http://opengroup.org/onlinepubs/9699919799/utilities/cal.html
6
7USE_CAL(NEWTOY(cal, ">2", TOYFLAG_USR|TOYFLAG_BIN))
8
9config CAL
10  bool "cal"
11  default y
12  help
13    usage: cal [[month] year]
14
15    Print a calendar.
16
17    With one argument, prints all months of the specified year.
18    With two arguments, prints calendar for month and year.
19*/
20
21#include "toys.h"
22
23// Write calendar into buffer: each line is 20 chars wide, end indicated
24// by empty string.
25
26static char *calstrings(char *buf, struct tm *tm)
27{
28  char temp[21];
29  int wday, mday, start, len, line;
30
31  // header
32  len = strftime(temp, 21, "%B %Y", tm);
33  len += (20-len)/2;
34  buf += sprintf(buf, "%*s%*s ", len, temp, 20-len, "");
35  buf++;
36  buf += sprintf(buf, "Su Mo Tu We Th Fr Sa ");
37  buf++;
38
39  // What day of the week does this month start on?
40  if (tm->tm_mday>1)
41    start = (36+tm->tm_wday-tm->tm_mday)%7;
42  else start = tm->tm_wday;
43
44  // What day does this month end on?  Alas, libc doesn't tell us...
45  len = 31;
46  if (tm->tm_mon == 1) {
47    int year = tm->tm_year;
48    len = 28;
49    if (!(year & 3) && !((year&100) && !(year&400))) len++;
50  } else if ((tm->tm_mon+(tm->tm_mon>6 ? 1 : 0)) & 1) len = 30;
51
52  for (mday=line=0;line<6;line++) {
53    for (wday=0; wday<7; wday++) {
54      char *pat = "   ";
55      if (!mday ? wday==start : mday<len) {
56        pat = "%2d ";
57        mday++;
58      }
59      buf += sprintf(buf, pat, mday);
60    }
61    buf++;
62  }
63
64  return buf;
65}
66
67// Worst case scenario toybuf usage: sizeof(struct tm) plus 21 bytes/line
68// plus 8 lines/month plus 12 months, comes to a bit over 2k of our 4k buffer.
69
70void cal_main(void)
71{
72  struct tm *tm;
73  char *buf = toybuf;
74
75  if (toys.optc) {
76    // Conveniently starts zeroed
77    tm = (struct tm *)toybuf;
78    buf += sizeof(struct tm);
79
80    // Last argument is year, one before that (if any) is month.
81    tm->tm_year = atolx_range(toys.optargs[--toys.optc], 1, 9999);
82    tm->tm_year -= 1900;
83    tm->tm_mday = 1;
84    tm->tm_hour = 12;  // noon to avoid timezone weirdness
85    if (toys.optc) {
86      tm->tm_mon = atolx_range(toys.optargs[--toys.optc], 1, 12);
87      tm->tm_mon--;
88
89    // Print 12 months of the year
90
91    } else {
92      char *bufs[12];
93      int i, j, k;
94
95      for (i=0; i<12; i++) {
96        tm->tm_mon=i;
97        mktime(tm);
98        buf = calstrings(bufs[i]=buf, tm);
99      }
100
101      // 4 rows, 6 lines each, 3 columns
102      for (i=0; i<4; i++) {
103        for (j=0; j<8; j++) {
104          for(k=0; k<3; k++) {
105            char **b = bufs+(k+i*3);
106            *b += printf("%s ", *b);
107          }
108          puts("");
109        }
110      }
111      return;
112    }
113
114    // What day of the week does that start on?
115    mktime(tm);
116
117  } else {
118    time_t now;
119    time(&now);
120    tm = localtime(&now);
121  }
122
123  calstrings(buf, tm);
124  while (*buf) buf += printf("%s\n", buf);
125}
126