How do I compare time in C? My program is getting the last modified time of 2 files, then compare that time to see which time is the latest. Is there a function that compares time for you, or you have to create one yourself? This is my get time function:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/stat.h>
#include <sys/types.h>
void getFileCreationTime(char *path) {
struct stat attr;
stat(path, &attr);
printf("Last modified time: %s", ctime(&attr.st_mtime));
}
Use difftime(time1, time0) from time.h to get the difference between two times. This calculates time1 - time0 and returns a double representing the difference in seconds. If it's positive, then time1 is later than time0; if negative, time0 is later; if 0, they're the same.
You can compare two time_t values to find which is newer:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/stat.h>
static time_t getFileModifiedTime(const char *path)
{
struct stat attr;
if (stat(path, &attr) == 0)
{
printf("%s: last modified time: %s", path, ctime(&attr.st_mtime));
return attr.st_mtime;
}
return 0;
}
int main(int argc, char **argv)
{
if (argc != 3)
{
fprintf(stderr, "Usage: %s file1 file2\n", argv[0]);
return 1;
}
time_t t1 = getFileModifiedTime(argv[1]);
time_t t2 = getFileModifiedTime(argv[2]);
if (t1 < t2)
printf("%s is older than %s\n", argv[1], argv[2]);
else if (t1 > t2)
printf("%s is newer than %s\n", argv[1], argv[2]);
else
printf("%s is the same age as %s\n", argv[1], argv[2]);
return 0;
}
If you want to know the difference between the values in seconds, then you need to use difftime() officially, but in practice you can simply subtract the two time_t values.
You can use below method
double difftime (time_t end, time_t beginning);
It returns the time difference in seconds. You can find example here.