Question

I am working on a C program where I need to get the last modified time of the file. What the program does is a function loops through each file within a directory and when a particular file(s) is found it calls another function to check that the last modified times of the file.

Within the directory there is a mylog.txt.1, mylog.txt.2 and mylog.txt.3 etc. When I list the directory in linux using the ll command I can see that mylog.txt.1 and mylog.txt.2 were modified on the 4th May and mylog.txt.3 was modified on the 3rd May.

When the program checks each of these files however, it is always returning 3rd may. Below is the code that I am using.

void getFileCreationTime(char *filePath)
{
    struct stat attrib;
    stat(filePath, &attrib);
    char date[10];
    strftime(date, 10, "%d-%m-%y", gmtime(&(attrib.st_ctime)));
    printf("The file %s was last modified at %s\n", filePath, date);
    date[0] = 0;
}

I’ve tried all the different variations of st_ctime, i.e. st_mtime and st_atime but they all return 3rd may.

Thanks for any help you can provide.

Answer 1

This is one of those cases where timezones matter. You’re getting gmtime of the st_mtime. You should instead be using localtime viz.

strftime(date, 20, "%d-%m-%y", localtime(&(attrib.st_ctime)));

this is because ls uses your timezone information, and when you used gmtime as part of the display, it deliberately omitted any timezone information.