yeah i think it has no bugs

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david committed 2026-09-28 11:15:28 -03:00
commit 2aaa9bbece
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timetolocal
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CC = gcc
CFLAGS = -Wall -Wextra -O2 -pipe
LDLIBS =
TARGET = timetolocal
SRC = $(wildcard *.c)
OBJ = $(SRC:src/%.c=obj/%.o)
PREFIX = /usr/local
all: $(TARGET)
$(TARGET): $(OBJ)
@mkdir -p $(@D)
$(CC) $(CFLAGS) -o $(TARGET) $(OBJ) $(LDLIBS)
install: $(TARGET)
install -D $(TARGET) $(DESTDIR)$(PREFIX)/bin/$(notdir $(TARGET))
uninstall:
rm -f $(DESTDIR)$(PREFIX)/bin/$(notdir $(TARGET))
obj/%.o: src/%.c
@mkdir -p $(@D)
$(CC) $(CFLAGS) -c $< -o $@
clean:
rm -rf obj/ $(TARGET)
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# timetolocal
converts a time from a different timezone to your local time.
## Build
make
## Usage
./timetolocal [TIME (24h)] [ZONE]
Example:
./timetolocal 7:15 est
Zone names are not case sensitive. abbreviations come from `tztable.h`
## Installing
sudo make install
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#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <time.h>
#include <stdlib.h>
#include "tztable.h"
/*it's not case sensitive
returns the offset
returns -1 if it doesn't find it*/
int findintable(char *what){
for(size_t i = 0; i < TZTABLE_LENGHT; i++){
if((strcasecmp(what, tz_table[i].zn)) == 0){
return tz_table[i].offset;
}
}
return -1;
}
davidtime strtimetoint(char *whattimeisit) {
davidtime timehoursandminutes = {0, 0};
if (whattimeisit == NULL)return timehoursandminutes;
char buf[16];
strncpy(buf, whattimeisit, sizeof(buf) - 1);
buf[sizeof(buf) - 1] = '\0';
char *token = strtok(buf, ":");
if (token == NULL) return timehoursandminutes;
timehoursandminutes.hour = atoi(token);
token = strtok(NULL, ":");
if (token == NULL) return timehoursandminutes;
timehoursandminutes.minutes = atoi(token);
return timehoursandminutes;
}
int convert(char *timey, char *zone){
time_t rawtime = time(NULL);
struct tm *ptm = gmtime(&rawtime);
ptm->tm_isdst = -1;
time_t gmt = mktime(ptm);
int offset = difftime(rawtime, gmt) / 60;
//this sould take even daylight savings too, i stole it from stack overflow i've been trying to not use llms to code shit like this
//tmzn hour --> utc00 --> local time
if(findintable(zone)== -1){
return -1;
}
int zntime = findintable(zone);
davidtime eugh = strtimetoint(timey);
int zonetimeminutes = (eugh.hour*60)+eugh.minutes;
int normalizedminutes = zonetimeminutes+(zntime*-1); //utc00
int localminutes = (normalizedminutes+offset) % 1440;
davidtime finally;
finally.hour = localminutes/60;
finally.minutes = localminutes - finally.hour*60;
printf("%02d:%02d\n",finally.hour,finally.minutes);
return 0;
}
int main (int argc, char **argv){
if((argc <= 2) || (argc > 3)){
printf("%s: usage: %s [TIME (24hs)] [ZONE]\ne.g: %s 7:15 est\n", argv[0], argv[0], argv[0]);
exit(0);
}
if(convert(argv [1], argv[2]) == -1){
printf("%s: time zone not found, did you write it correctly?\n", argv[0]);
return 1;
}else return 0;
}
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#ifndef TZTABLE_H
#define TZTABLE_H
#include <stddef.h>
typedef struct davidtime{
int hour;
int minutes;
}davidtime;
//offset is minutes from UTC (there are duplicates so first match wins on a linear scan)
struct tztable{
const char *zn;
int offset;
};
static const struct tztable tz_table[] = {
{"ACDT", 630}, {"ACST", 570}, {"ACT", -300}, {"ACT", 480}, {"ACWST", 525},
{"ADT", -180}, {"AEDT", 660}, {"AEST", 600}, {"AFT", 270}, {"AKDT", -480},
{"AKST", -540}, {"ALMT", 360}, {"AMST", -180}, {"AMT", -240}, {"AMT", 240},
{"ANAT", 720}, {"AQTT", 300}, {"ART", -180}, {"AST", 180}, {"AST", -240},
{"AWST", 480}, {"AZOST", 0}, {"AZOT", -60}, {"AZT", 240}, {"BNT", 480},
{"BIOT", 360}, {"BIT", -720}, {"BOT", -240}, {"BRST", -120}, {"BRT", -180},
{"BST", 360}, {"BST", 660}, {"BST", 60}, {"BTT", 360}, {"CAT", 120},
{"CCT", 390}, {"CDT", -300}, {"CDT", -240}, {"CEST", 120}, {"CET", 60},
{"CHADT", 825}, {"CHAST", 765}, {"CHOT", 480}, {"CHOST", 540}, {"CHST", 600},
{"CHUT", 600}, {"CIST", -480}, {"CKT", -600}, {"CLST", -180}, {"CLT", -240},
{"COST", -240}, {"COT", -300}, {"CST", -360}, {"CST", 480}, {"CST", -300},
{"CVT", -60}, {"CWST", 525}, {"CXT", 420}, {"DAVT", 420}, {"DDUT", 600},
{"DFT", 60}, {"EASST", -300},{"EAST", -360}, {"EAT", 180}, {"ECT", -240},
{"ECT", -300}, {"EDT", -240}, {"EEST", 180}, {"EET", 120}, {"EGST", 0},
{"EGT", -60}, {"EST", -300}, {"FET", 180}, {"FJT", 720}, {"FKST", -180},
{"FKT", -240}, {"FNT", -120}, {"GALT", -360}, {"GAMT", -540}, {"GET", 240},
{"GFT", -180}, {"GILT", 720}, {"GIT", -540}, {"GMT", 0}, {"GST", -120},
{"GST", 240}, {"GYT", -240}, {"HDT", -540}, {"HAEC", 120}, {"HST", -600},
{"HKT", 480}, {"HMT", 300}, {"HOVST", 480}, {"HOVT", 420}, {"ICT", 420},
{"IDLW", -720}, {"IDT", 180}, {"IOT", 360}, {"IRDT", 270}, {"IRKT", 480},
{"IRST", 210}, {"IST", 330}, {"IST", 60}, {"IST", 120}, {"JST", 540},
{"KALT", 120}, {"KGT", 360}, {"KOST", 660}, {"KRAT", 420}, {"KST", 540},
{"LHST", 630}, {"LHST", 660}, {"LINT", 840}, {"MAGT", 720}, {"MART", -570},
{"MAWT", 300}, {"MDT", -360}, {"MET", 60}, {"MEST", 120}, {"MHT", 720},
{"MIST", 660}, {"MIT", -570}, {"MMT", 390}, {"MSK", 180}, {"MST", 480},
{"MST", -420}, {"MUT", 240}, {"MVT", 300}, {"MYT", 480}, {"NCT", 660},
{"NDT", -150}, {"NFT", 660}, {"NOVT", 420}, {"NPT", 345}, {"NST", -210},
{"NT", -210}, {"NUT", -660}, {"NZDT", 780}, {"NZDST", 780}, {"NZST", 720},
{"OMST", 360}, {"ORAT", 300}, {"PDT", -420}, {"PET", -300}, {"PETT", 720},
{"PGT", 600}, {"PHOT", 780}, {"PHT", 480}, {"PHST", 480}, {"PKT", 300},
{"PMDT", -120}, {"PMST", -180}, {"PONT", 660}, {"PST", -480}, {"PWT", 540},
{"PYST", -180}, {"PYT", -240}, {"RET", 240}, {"ROTT", -180}, {"SAKT", 660},
{"SAMT", 240}, {"SAST", 120}, {"SBT", 660}, {"SCT", 240}, {"SDT", -600},
{"SGT", 480}, {"SLST", 330}, {"SRET", 660}, {"SRT", -180}, {"SST", -660},
{"SYOT", 180}, {"TAHT", -600}, {"THA", 420}, {"TFT", 300}, {"TJT", 300},
{"TKT", 780}, {"TLT", 540}, {"TMT", 300}, {"TRT", 180}, {"TOT", 780},
{"TST", 480}, {"TVT", 720}, {"ULAST", 540}, {"ULAT", 480}, {"UTC", 0},
{"UYST", -120}, {"UYT", -180}, {"UZT", 300}, {"VET", -240}, {"VLAT", 600},
{"VOLT", 180}, {"VOST", 360}, {"VUT", 660}, {"WAKT", 720}, {"WAST", 120},
{"WAT", 60}, {"WEST", 60}, {"WET", 0}, {"WIB", 420}, {"WIT", 540},
{"WITA", 480}, {"WGST", -120}, {"WGT", -180}, {"WST", 480}, {"YAKT", 540},
{"YEKT", 300},
};
#define TZTABLE_LENGHT (sizeof(tz_table) / sizeof(tz_table[0]))
#endif