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twc.c
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twc.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>
#include <time.h>
#include <unistd.h>
#define _POSIX_C_SOURCE 200809L
#define STR_LENGTH 32
enum {
TIMEFMT_ISO, TIMEFMT_HUMAN, NTIMEFMT
};
const char *time_fmts[NTIMEFMT] = {
"%FT%T%z", "%F %T %z"
};
const char *file = "/twc/tz.conf";
static void usage(const char *s) {
fprintf(stderr,
"usage: %s [-h] [-f path] [-s format] [-t timezone] ...\n\n"
"Options:\n"
" -f path\n"
" Read config from path (default \"$HOME/.config/twc/tz.conf\")\n"
" -h Print in human-readable format\n"
" -s format\n"
" Set desired time format (e.g. \"%%Y-%%m-%%d\")\n"
" -t timezone\n"
" Set a specific timezone (e.g. \"Asia/Tokyo\")\n",
s);
exit(EXIT_FAILURE);
}
static void errmsg(const char *msg) {
fprintf(stderr, "error: %s\n", msg);
exit(EXIT_FAILURE);
}
static void fparse(const char *s, const char *fpath, const char *fmt) {
char timestr[STR_LENGTH], *line = NULL, *path = NULL;
size_t len = 0;
FILE *fp;
if (!fpath && !fmt) {
char *home = getenv("XDG_CONFIG_HOME");
home = (!home || !*home) ? getenv("HOME") : home;
if (!home || !*home)
errmsg("could not get the value of the $HOME variable");
char *conf = home == getenv("HOME") ? "/.config" : "";
size_t sizet = strlen(home) + strlen(conf) + strlen(file) + 1;
path = calloc(sizet, sizeof(char));
snprintf(path, sizet, "%s%s%s", home, conf, file);
fpath = path;
}
time_t t;
time(&t);
if (fmt) {
setenv("TZ", fmt, 1);
strftime(timestr, sizeof(timestr), s, localtime(&t));
printf("%s\n", timestr);
free(path);
return;
}
fp = fopen(fpath, "r");
if (!fp) {
line = "UTC";
setenv("TZ", line, 1);
strftime(timestr, sizeof(timestr), s, gmtime(&t));
size_t width = strlen(line) + 2;
printf("%-*s\n", (int)width, timestr);
free(path);
return;
}
size_t max_width = 0;
while (getline(&line, &len, fp) != -1) {
if (*line == '#' || *line == '\n')
continue;
size_t width = strlen(line);
if (width > max_width)
max_width = width;
}
max_width++;
rewind(fp);
while (getline(&line, &len, fp) != -1) {
if (*line == '#' || *line == '\n')
continue;
char *nl = strchr(line, '\n');
if (nl)
*nl = '\0';
setenv("TZ", line, 1);
strftime(timestr, sizeof(timestr), s, localtime(&t));
printf("%-*s%s\n", (int)max_width, line, timestr);
}
free(line);
free(path);
fclose(fp);
}
int main(int argc, char **argv) {
int opt;
const char *progname = basename(argv[0]),
*timefmt = time_fmts[TIMEFMT_ISO], *fpath = NULL, *fmt = NULL;
const char *tz_env = getenv("TZ");
if (tz_env)
fmt = tz_env;
while ((opt = getopt(argc, argv, "hf:s:t:")) != -1) {
switch (opt) {
case 'h':
timefmt = time_fmts[TIMEFMT_HUMAN];
break;
case 'f':
fpath = optarg;
break;
case 's':
timefmt = optarg;
break;
case 't':
fmt = optarg;
break;
default:
usage(progname);
}
}
fparse(timefmt, fpath, fmt);
}