4 ms·

I am under the impression that modifying a file's content updates the modification time. Is this incorrect? Modifying a file without updating the mtime or allow

• mixmastamyk 3y ago
  Yes it does. mtimes can definitely be edited, if you have permission, but it is rare. I have a photo script that pulls the taken time from Exif and writes it to the file mtime.
  • hddqsb 3y ago
    > mtimes can definitely be edited, if you have permission It just requires you to be the owner of the file (https://serverfault.com/a/337810 https://serverfault.com/a/337810), no special permissions. On the other hand, editing the ctime is not easy -- it requires tricks (e.g. change the computer clock, which typically requires root privileges).
• hddqsb 3y ago
  On Linux, the mtime ("modification time") is indeed automatically updated when the content is changed, but it can also be set arbitrarily from userspace (e.g. using `touch`) without special permissions. This is very useful, e.g. when you mirror a directory you'll typically want to preserve the mtimes, to help identify changes later. Linux also has a ctime ("status change time"), which is automatically updated when the content or metadata (inode) are changed. It is not possible to change from userspace (you have to use tricks such as changing the computer clock or directly modifying the disk). This gives you the security benefits, but it is not commonly used e.g. in backup tools, precisely because they want to be able to set "fake" timestamps.