src/strftime.c

   1 /*
   2
   3 strftime.c -- provide strftime functionality on the command line
   4 Copyright (C) 2016,2017 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 1.2.0\n" \
  24 "Copyright (C) 2016,2017 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 "The %N format specifier is also supported for a 9-digit nanoseconds but the\n" \
  46 "last three digits will always be zero in this implementation and only the first\n" \
  47 "occurrence of %N will be replaced.  Additionally, if the current time is used\n" \
  48 "along with %N then a 1 ms sleep will occur before and after gettimeofday().\n"
  49
  50 #include <stdio.h>
  51 #include <stdlib.h>
  52 #include <locale.h>
  53 #include <string.h>
  54 #include <time.h>
  55 #include <sys/time.h>
  56
  57 #define DEFAULT_FORMAT "%a, %e %b %Y %T %z"
  58 #define MAXLENGTH 4096
  59
  60 static char buff[MAXLENGTH];
  61 static char tzval[20]; /* TZ=unknown+HH:MM:SS\0 */
  62
  63 int main(int argc, char *argv[])
  64 {
  65         int arg = 1;
  66         char *bp = buff;
  67         struct timeval tv;
  68         char *fmt = DEFAULT_FORMAT;
  69         int defaultformat = 1;
  70         int dosetlocale = 0;
  71         int needtime = 1;
  72         struct tm localvals;
  73         long adjust = 0;
  74         size_t fmtlen, i, firstN;
  75
  76         tv.tv_usec = 0;
  77         while (arg < argc && *argv[arg] == '-') {
  78                 if (!strcmp(argv[arg], "--help") || !strcmp(argv[arg], "-h")) {
  79                         printf("%s", USAGE);
  80                         return 0;
  81                 }
  82                 if (!strcmp(argv[arg], "--version") || !strcmp(argv[arg], "-V")) {
  83                         printf("%s", VERSION);
  84                         return 0;
  85                 }
  86                 if (!strcmp(argv[arg], "--locale") || !strcmp(argv[arg], "-l")) {
  87                         dosetlocale = 1;
  88                         ++arg;
  89                         continue;
  90                 }
  91                 if (!strcmp(argv[arg], "--adjust") || !strcmp(argv[arg], "-a")) {
  92                         char *end;
  93
  94                         if (++arg >= argc || !*argv[arg]) {
  95                                 fprintf(stderr, "strftime: missing --adjust value "
  96                                         "(see strftime -h)\n");
  97                                 return 1;
  98                         }
  99                         adjust = strtol(argv[arg], &end, 10);
 100                         if (*end) {
 101                                 fprintf(stderr, "strftime: invalid number: %s\n",
 102                                         argv[arg]);
 103                                 return 2;
 104                         }
 105                         ++arg;
 106                         continue;
 107                 }
 108                 if (!strcmp(argv[arg], "--")) {
 109                         ++arg;
 110                         break;
 111                 }
 112                 fprintf(stderr, "strftime: invalid option: %s (see strftime -h)\n",
 113                         argv[arg]);
 114                 return 1;
 115         }
 116         if (argc - arg > 3) {
 117                 fprintf(stderr, "strftime: invalid arguments (see strftime -h)\n");
 118                 return 1;
 119         }
 120         if (argc - arg >= 1) {
 121                 if (*argv[arg]) {
 122                         fmt = argv[arg];
 123                         defaultformat = 0;
 124                 }
 125                 if (argc - arg >= 2) {
 126                         if (*argv[arg+1]) {
 127                                 char *end;
 128                                 long l = strtol(argv[arg+1], &end, 10);
 129
 130                                 if (*end) {
 131                                         fprintf(stderr, "strftime: invalid number: %s\n",
 132                                                 argv[arg+1]);
 133                                         return 2;
 134                                 }
 135                                 tv.tv_sec = (time_t)l;
 136                                 needtime = 0;
 137                         }
 138                         if (argc - arg >= 3) {
 139                                 const char *o = argv[arg+2];
 140                                 size_t l = strlen(o);
 141                                 char tzsign = '-';
 142                                 char *d = tzval;
 143
 144                                 if (*o == '+' || *o == '-') {
 145                                         tzsign = (*o == '+') ? '-' : '+';
 146                                         ++o;
 147                                         --l;
 148                                 }
 149                                 if (l < 2 || l > 6 || (l & 0x1) || l != strspn(o, "0123456789")) {
 150                                         fprintf(stderr, "strftime: invalid offset: %s\n",
 151                                                 argv[arg+2]);
 152                                         return 2;
 153                                 }
 154                                 if (l == strspn(o, "0")) {
 155                                         memcpy(d, "TZ=UTC", 6);
 156                                         d += 6;
 157                                 } else {
 158                                         memcpy(d, "TZ=unknown", 10);
 159                                         d += 10;
 160                                         *d++ = tzsign;
 161                                         *d++ = *o++;
 162                                         *d++ = *o++;
 163                                         if (*o) {
 164                                                 *d++ = ':';
 165                                                 *d++ = *o++;
 166                                                 *d++ = *o++;
 167                                         }
 168                                         if (*o) {
 169                                                 *d++ = ':';
 170                                                 *d++ = *o++;
 171                                                 *d++ = *o++;
 172                                         }
 173                                 }
 174                                 *d = '\0';
 175                                 putenv(tzval);
 176                         }
 177                 }
 178         }
 179         if (dosetlocale) {
 180                 setlocale(LC_ALL, "");
 181         }
 182         tzset();
 183         fmtlen = strlen(fmt);
 184         firstN = 0;
 185         for (i=0; i<fmtlen; ++i) {
 186                 if (fmt[i] != '%')
 187                         continue;
 188                 ++i;
 189                 if (fmt[i] == '%')
 190                         continue;
 191                 if (fmt[i] == 'N') {
 192                         fmt[i-1] = '\0';
 193                         firstN = i + 1;
 194                         break;
 195                 }
 196         }
 197         if (needtime) {
 198                 struct timespec milli;
 199                 if (firstN) {
 200                         milli.tv_sec = 0;
 201                         milli.tv_nsec = 1000;
 202                         nanosleep(&milli, NULL);
 203                 }
 204                 gettimeofday(&tv, NULL);
 205                 if (firstN)
 206                         nanosleep(&milli, NULL);
 207         }
 208         tv.tv_sec += (time_t)adjust;
 209         localvals = *localtime(&tv.tv_sec);
 210         buff[0] = '\0';
 211         if (*fmt && !strftime(buff, sizeof(buff), fmt, &localvals)) {
 212                 fprintf(stderr, "strftime: format string too long\n");
 213                 return 3;
 214         }
 215         if (firstN) {
 216                 size_t left = sizeof(buff) - (fmtlen = strlen(buff));
 217                 if (left < 10) {
 218                         fprintf(stderr, "strftime: format string too long\n");
 219                         return 3;
 220                 }
 221                 snprintf(buff + fmtlen, left, "%06u000", (unsigned)tv.tv_usec);
 222                 fmtlen += 9;
 223                 left -= 9;
 224                 fmt += firstN;
 225                 if (*fmt) {
 226                         if (!strftime(buff + fmtlen, left, fmt, &localvals)) {
 227                                 fprintf(stderr, "strftime: format string too long\n");
 228                                 return 3;
 229                         }
 230                 }
 231         }
 232         if (defaultformat && !dosetlocale && buff[3] == ',' && buff[5] == ' ') {
 233                 memmove(buff+1, buff, 4);
 234                 ++bp;
 235         }
 236         printf("%s\n", bp);
 237         return 0;
 238 }