date.c

   1 /*
   2     Copyright © 2013 Alastair Stuart
   3
   4     This program is open source software: you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation, either version 3 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  12     GNU General Public License for more details.
  13 */
  14
  15 #include <stdio.h>
  16 #include <time.h>
  17 #include <stdbool.h>
  18 #include <string.h>
  19
  20 #define VERSION "0.01"
  21
  22 struct {
  23     bool iso;
  24     bool utc;
  25 } flags;
  26
  27 char string[128+1] = {'\0'};
  28 char* format = "%a %b %d %X %Z %Y";
  29
  30 int main(int argc, char* argv[])
  31 {
  32     flags.iso = false;
  33     flags.utc = false;
  34
  35     // flag parsing
  36     int arg = 0;
  37     for (arg = 1; arg < argc; arg++)
  38     {
  39         if (strcmp("--iso", argv[arg]) == 0 || strcmp("-I", argv[arg]) == 0) {
  40             flags.iso = true;
  41         } else if (strcmp("--utc", argv[arg]) == 0 || strcmp("-u", argv[arg]) == 0) {
  42             flags.utc = true;
  43         } else if (strcmp("--help", argv[arg]) == 0 || strcmp("-h", argv[arg]) == 0) {
  44             printf("Usage: %s [options ...] [+format]\n", argv[0]);
  45             printf("\n"
  46                    "    -I, --iso               Print time in ISO 8601 format.\n"
  47                    "    -u, --utc               Print time in UTC instead of localtime.\n"
  48                    "\n"
  49                    "    -h, --help              Print this message.\n"
  50                    "    -v, --version           Show version info.\n");
  51             return 0;
  52         } else if (strcmp("--version", argv[arg]) == 0 || strcmp("-v", argv[arg]) == 0) {
  53             printf("date (mutos) v"VERSION"\n");
  54             return 0;
  55         } else {
  56             // no more flags left
  57             break;
  58         }
  59     }
  60
  61     if ((argc - arg) > 1) {
  62         fprintf(stderr, "%s: too many arguments\n",
  63                          argv[0]);
  64         return 1;
  65     } else if ((argc - arg) == 1) {
  66         if (argv[arg][0] != '+') {
  67             fprintf(stderr, "%s: invalid format\n",
  68                              argv[0]);
  69             return 1;
  70         } else if (flags.iso){
  71             fprintf(stderr, "%s: multiple formats given\n",
  72                              argv[0]);
  73             return 1;
  74         } else {
  75             format = argv[arg] + 1;
  76         }
  77     }
  78
  79     time_t curr_time = time(NULL);
  80     struct tm *now = NULL;
  81     if (flags.utc) {
  82         now = gmtime(&curr_time);
  83     } else {
  84         now = localtime(&curr_time);
  85     }
  86
  87     if (flags.iso) {
  88         format = "%Y-%m-%dT%X%z";
  89     }
  90
  91     strftime(string, 128, format, now);
  92
  93     printf("%s\n", string);
  94
  95     return 0;
  96 }