Time convert from a file and compare to the current time - c

Question

I've asked something close to this before, but as it seems, the time I get from the file does not convert to the same type of time you get from localtime() and time().
Exactly what I want is:
I have a txt file with the following information
order.txt
file1.txt;5;15:40
file2.txt;7;15:41
file1.txt;10;16:00
My objective is to get the time in hour:min (15:40) and then, if it's the same as the currentTime, then I show the file1.txt content. Otherwise, if the currentTime is lower than the hour:min time (15:40), it waits untill it's 15:40 and shows the file1.txt content. If the currentTime is higher, then it ignores the first one and goes to the next one.
So for example, if the current time is 15:39, it will wait 1 minute and then show the file1.txt content.
If the current Time is 15:40, it shows the file1.txt content without waiting.
If the current Time is 15:41, it just goes to the next one (file2.txt) and checks again.
Used variables
FILE* orderFile;
FILE* contentFile;
FILE* defaultFile; (This will be used when this code works)
char fileName[50];
char textContent[5000];
int seconds;
int hour, min;
int diff_time;
char timeValue[50];
time_t current;
Includes
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
So for that I've tried the following code:
orderFile = fopen("order.txt","r");
defaultFile = fopen("default.txt","r");
while(fscanf(orderFile," %49[^;];%d; %49[^\n]",fileName,&seconds,timeValue)
{
sscanf(timeValue,"%d:%d",&hour,&min);
contentFile = fopen(fileName,"r");
if(contentFile != NULL)
{
fseek (contentFile, 0, SEEK_END);
size = ftell(contentFile);
rewind(contentFile);
if(size == 0)
{
printf("\nEmpty file. (Scanned file: %s)\n", fileName);
fclose(contentFile);
}
else
{
time_t now;
time(&now);
struct tm file_time_tm;
file_time_tm = *localtime(&now);
file_time_tm.tm_hour = hour;
file_time_tm.tm_min = min;
file_time_tm.tm_sec = 0;
file_time_tm.tm_isdst = -1;
time_t fileTime = mktime(&file_time_tm);
double diff_time = difftime(fileTime, now);
if(diff_time == 0)
{
while(fscanf(contentFile,"%[^\t]",textContent) == 1)
{
printf("%s\n", textContent);
}
sleep(seconds);
}
else
{
if(diff_time > 0)
{
while(fscanf(defaultFile,"%[^\t]",defaultContent) == 1)
{
printf("%s\n", defaultContent);
}
sleep(diff_time);
while(fscanf(contentFile,"%[^\t]",textContent) == 1)
{
printf("%s\n", textContent);
}
sleep(seconds);
}
}
fclose(defaultFile);
fclose(contentFile);
}
}
else
{
if(contentFile == NULL)
{
printf("\nFile does not exist. (Scanned file: %s)\n", fileName);
fclose(contentFile);
}
}
}
fclose(orderFile);
printf("\n");
So thanks to chux it is quite working now, yet not fully working.
If I have the following:
Current Time: 15:00
order.txt
file1.txt;5;15:01
file2.txt;6;15:02
file3.txt;3;15:03
When I run the program, the following will occur:
DEFAULT MESSAGE (text inside default.txt)
WAITS DIFF_TIME (CORRECTLY DONE)
SHOWS CONTENT FROM THE file1.txt
WAITS 5 SECONDS
X - SHOWS CONTENT FROM THE file2.txt (This is wrong, it should check again and if the time is 15:02 it will show, not 15:01. Which I assume it's because it is still reading as 15:01 on the timeValue and not 15:02, any idea why?)
WAITS UNTILL IT'S 15:02 (wrong)
SHOWS file3.txt (wrong)
WAITS UNTILL IT'S 15:03
ENDS (wrong as it should not end after waiting, it should end when file3.txt shows and waits for 3 seconds)
Output I need:
DEFAULT MESSAGE
waits diff_time
file1.txt content
waits 5 seconds
DEFAULT MESSAGE
waits diff_time
file2.txt content
waits 7 seconds
DEFAULT MESSAGE
waits diff_time
file3.txt content
waits 3 seconds
ENDS
It also does not work well if I have two files with the same time, such as this:
order.txt
file1.txt;5;15:01
file2.txt;6;15:01
file3.txt;3;15:02
It breaks it aswell.
Any idea of how to do this correctly?

Answer 1

As commented above by #M Oehm, it is apparent the compiler warnings are not fully enabled. Suggest enabling them - it will save you time.
A problem lies in the time compare and subtraction.
// Troublesome code
if(currentTime->tm_hour < hour && currentTime->tm_min < min) {
diff_time = difftime(currentTime,timeValue);
printf("%d - Or this?\n", diff_time);
sleep(diff_time);
}
The comparison is curious. Usually with such a comparison would be in the form
if (h1 < h2 || (h1 == h2 && m1 < m2))
difftime takes 2 time_t paramters, not char timeValue[50] and a struct tm.
The values passed to double difftime(time_t time1, time_t time0) appear backwards. The result it time1 - time0.
Recommend instead
int current_hm = currentTime->tm_hour * 60 + currentTime->tm_min;
int file_hm = hour * 60 + min;
if (current_hm < file_hm) {
unsigned diff_time = (file_hm - current_hm)*60u;
printf("%u - Or this?\n", diff_time);
sleep(diff_time);
}
[Edit]
Simplified approach.
time_t now;
time(&now);
struct tm file_time_tm;
file_time_tm = *localtime(&now);
file_time_tm.tm_hour = hour; // from file
file_time_tm.tm_min = min; // from file
file_time_tm.tm_sec = 0;
file_time_tm.tm_isdst = -1;
time_t filetime = mktime(&file_time_tm);
double diff = difftime(filetime, now); // filetime - now
if (diff > 0) {
sleep((unsigned) diff);
}

Answer 2

Chux's suggestion to do your comparisons with your own integer that represents the minutes after midnight is probably easier in your case, but if you want to use the standard time mechanisms, you can do it.
But first, keep in mind that there are two time representations, time_t, which is a "numerical" time that stores the seconds after the epoch and struct tm, which is the human-readable time that breaks a time down to years, months, days and so on.
With strptime, you can scan a string accoding to a format specification. It is the scanf for struct tm. This function does not initialise fields that are not specified, so that you can assign the current time with localtime and then overwrite only the hour and minute fields.
mktime converts a struct tm to a time_t, which you can pass to difftime.
The following code snipped shows how such a comparison might work:
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
int main()
{
char stamp[] = "12:53";
char *p;
struct tm now;
time_t t = time(NULL);
now = *localtime(&t);
p = strptime(stamp, "%H:%M", &now);
if (p == NULL || *p != '\0') {
printf("Illegal date.\n");
} else {
char buf[20];
double dsec;
int dmin;
strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M\n", &now);
puts(buf);
dsec = difftime(t, mktime(&now));
printf("Diff: %g sec\n", dsec);
dmin = (int) dsec / 60;
printf("Diff: %d min\n", dmin);
}
return 0;
}