src/strftime.c

   1 /*
   2
   3 strftime.c -- provide strftime functionality on the command line
   4 Copyright (C) 2016 Kyle J. McKay.  All rights reserved.
   5
   6 This program is free software; you can redistribute it and/or
   7 modify it under the terms of the GNU General Public License
   8 as published by the Free Software Foundation; either version 2
   9 of the License, or (at your option) any later version.
  10
  11 This program is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with this program; if not, write to the Free Software
  18 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  19
  20 */
  21
  22 #define VERSION \
  23 "strftime version 1.1.0\n" \
  24 "Copyright (C) 2016 Kyle J. McKay <mackyle at gmail dot com>\n" \
  25 "License GPLv2+: GNU GPL version 2 or later.\n" \
  26 "<http://gnu.org/licenses/gpl2.html>\n" \
  27 "This is free software: you are free to change and redistribute it.\n" \
  28 "There is NO WARRANTY, to the extent permitted by law.\n"
  29
  30 #define USAGE \
  31 "Usage: strftime [option...] [\"strftime(3) format\" [<epochsecs> [<offset>]]]\n" \
  32 "  --help/-h     show this help\n" \
  33 "  --version/-V  show version/license info\n" \
  34 "  --locale/-l   use default locale rather than \"C\" locale\n" \
  35 "  --adjust/-a n add n (which may be negative) to <epochsecs> before formatting\n" \
  36 "  --            terminate options, next arg is format even if it starts with -\n" \
  37 "  <epochsecs>   if omitted or empty string ('') use current time\n" \
  38 "  <offset>      must be [+|-]HH[MM[SS]] same meaning as strftime(3) '%z' value\n" \
  39 "If \"strftime(3) format\" is omitted (or '') then \"%a, %e %b %Y %T %z\" is used.\n" \
  40 "If <offset> is omitted default timezone (taking TZ into account) will be used.\n" \
  41 "If <offset> is NOT omitted then a strftime(3) '%Z' value will format as either\n" \
  42 "\"unknown\" or \"UTC\" (for a zero offset).  Note that except for the time zone\n" \
  43 "name, `date` and `strftime '%a %b %e %T %Z %Y' $(date +'%s %z')` should match.\n" \
  44 "If --locale is NOT used the default format strips leading spaces from %e value.\n"
  45
  46 #define _XOPEN_SOURCE
  47 #include <stdio.h>
  48 #include <stdlib.h>
  49 #include <locale.h>
  50 #include <string.h>
  51 #include <time.h>
  52
  53 #define DEFAULT_FORMAT "%a, %e %b %Y %T %z"
  54 #define MAXLENGTH 4096
  55
  56 static char buff[MAXLENGTH];
  57 static char tzval[20]; /* TZ=unknown+HH:MM:SS\0 */
  58
  59 int main(int argc, char *argv[])
  60 {
  61         int arg = 1;
  62         char *bp = buff;
  63         time_t t = time(NULL);
  64         const char *fmt = DEFAULT_FORMAT;
  65         int defaultformat = 1;
  66         int dosetlocale = 0;
  67         struct tm localvals;
  68         long adjust = 0;
  69
  70         while (arg < argc && *argv[arg] == '-') {
  71                 if (!strcmp(argv[arg], "--help") || !strcmp(argv[arg], "-h")) {
  72                         printf("%s", USAGE);
  73                         return 0;
  74                 }
  75                 if (!strcmp(argv[arg], "--version") || !strcmp(argv[arg], "-V")) {
  76                         printf("%s", VERSION);
  77                         return 0;
  78                 }
  79                 if (!strcmp(argv[arg], "--locale") || !strcmp(argv[arg], "-l")) {
  80                         dosetlocale = 1;
  81                         ++arg;
  82                         continue;
  83                 }
  84                 if (!strcmp(argv[arg], "--adjust") || !strcmp(argv[arg], "-a")) {
  85                         char *end;
  86
  87                         if (++arg >= argc || !*argv[arg]) {
  88                                 fprintf(stderr, "strftime: missing --adjust value "
  89                                         "(see strftime -h)\n");
  90                                 return 1;
  91                         }
  92                         adjust = strtol(argv[arg], &end, 10);
  93                         if (*end) {
  94                                 fprintf(stderr, "strftime: invalid number: %s\n",
  95                                         argv[arg]);
  96                                 return 2;
  97                         }
  98                         ++arg;
  99                         continue;
 100                 }
 101                 if (!strcmp(argv[arg], "--")) {
 102                         ++arg;
 103                         break;
 104                 }
 105                 fprintf(stderr, "strftime: invalid option: %s (see strftime -h)\n",
 106                         argv[arg]);
 107                 return 1;
 108         }
 109         if (argc - arg > 3) {
 110                 fprintf(stderr, "strftime: invalid arguments (see strftime -h)\n");
 111                 return 1;
 112         }
 113         if (argc - arg >= 1) {
 114                 if (*argv[arg]) {
 115                         fmt = argv[arg];
 116                         defaultformat = 0;
 117                 }
 118                 if (argc - arg >= 2) {
 119                         if (*argv[arg+1]) {
 120                                 char *end;
 121                                 long l = strtol(argv[arg+1], &end, 10);
 122
 123                                 if (*end) {
 124                                         fprintf(stderr, "strftime: invalid number: %s\n",
 125                                                 argv[arg+1]);
 126                                         return 2;
 127                                 }
 128                                 t = (time_t)l;
 129                         }
 130                         if (argc - arg >= 3) {
 131                                 const char *o = argv[arg+2];
 132                                 size_t l = strlen(o);
 133                                 char tzsign = '-';
 134                                 char *d = tzval;
 135
 136                                 if (*o == '+' || *o == '-') {
 137                                         tzsign = (*o == '+') ? '-' : '+';
 138                                         ++o;
 139                                         --l;
 140                                 }
 141                                 if (l < 2 || l > 6 || (l & 0x1) || l != strspn(o, "0123456789")) {
 142                                         fprintf(stderr, "strftime: invalid offset: %s\n",
 143                                                 argv[arg+2]);
 144                                         return 2;
 145                                 }
 146                                 if (l == strspn(o, "0")) {
 147                                         memcpy(d, "TZ=UTC", 6);
 148                                         d += 6;
 149                                 } else {
 150                                         memcpy(d, "TZ=unknown", 10);
 151                                         d += 10;
 152                                         *d++ = tzsign;
 153                                         *d++ = *o++;
 154                                         *d++ = *o++;
 155                                         if (*o) {
 156                                                 *d++ = ':';
 157                                                 *d++ = *o++;
 158                                                 *d++ = *o++;
 159                                         }
 160                                         if (*o) {
 161                                                 *d++ = ':';
 162                                                 *d++ = *o++;
 163                                                 *d++ = *o++;
 164                                         }
 165                                 }
 166                                 *d = '\0';
 167                                 putenv(tzval);
 168                         }
 169                 }
 170         }
 171         if (dosetlocale) {
 172                 setlocale(LC_ALL, "");
 173         }
 174         tzset();
 175         t += (time_t)adjust;
 176         localvals = *localtime(&t);
 177         if (!strftime(buff, sizeof(buff), fmt, &localvals)) {
 178                 fprintf(stderr, "strftime: format string too long\n");
 179                 return 3;
 180         }
 181         if (defaultformat && !dosetlocale && buff[3] == ',' && buff[5] == ' ') {
 182                 memmove(buff+1, buff, 4);
 183                 ++bp;
 184         }
 185         printf("%s\n", bp);
 186         return 0;
 187 }