Compare two times in C

Question

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));
}

Answer 1

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.

Answer 2

my code:

char * findLeastFile(char *file1, char *file2){
    struct stat attr1, attr2;
    if (stat(file1, &attr1) != 0 || stat(file2, &attr2) != 0)
    {
        printf("file excetion");
        return NULL;
    }
    if(difftime(attr1.st_mtime,attr2.st_mtime) >= 0)
        return file1;
    else 
        return file2;

}