Checking the modification date does not work

Question

I have a problem with checking the modification date. fprintf prints in the console for every file in the folder the same number equal zero.

while (1) {
    source = opendir(argv[1]);
    while ((file = readdir(source)) != NULL) {
        if (file->d_type != DT_REG)
            continue; 
        stat(file->d_name, &file_details);
        fprintf(stderr, "Name: %s, Last modify: %ld  \n", file->d_name, file_details.st_mtime);
    }
    closedir(source);
    sleep(5);
}

Error checking! You don't have any. You need to add it. My guess is that `stat` returns `-1` with `errno == ENOENT`. — Some programmer dude, Apr 03 '19 at 08:23
And a hint about what I think is the problem: `file->d_name` is just the file-name, not a full path. — Some programmer dude, Apr 03 '19 at 08:24
@kamilm758 You have to build it by concatenating the directory name and the file name, with `/` inbetween of course. Another way is to enter the directory being scanned, with `chdir()`. — unwind, Apr 03 '19 at 08:36

chqrlie · Answer 1 · 2019-04-03T15:40:33.037

You must construct the path to the directory entry ans pass it to stat. You currently pass the entry name, which only works if you are enumerating from the current directory.

Furthermore, you should test the return value of stat to detect any problem. This would have shown that stat fails with the current code.

Here is a modified version:

#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>

...

char path[1024];
while (1) {
    source = opendir(argv[1]);
    if (source == NULL)
        break;
    while ((file = readdir(source)) != NULL) {
        if (file->d_type != DT_REG)
            continue; 
        snprintf(path, sizeof path, "%s/%s", path, file->d_name);
        if (!stat(path, &file_details))
            fprintf(stderr, "Name: %s, Last modify: %ld\n", path, file_details.st_mtime);
        else
            fprintf(stderr, "Cannot stat %s; %s\n", path, strerror(errno));
    }
    closedir(source);
    sleep(5);
}

If date of modification is bigger then file was modified later? — kamilm758, Apr 03 '19 at 09:35

Checking the modification date does not work

1 Answers1