Linux - modify file modify/access/change time [closed]

Question

I read an article about new steganographic method: "Time is on my side: Steganography in filesystem metadata" http://www.sciencedirect.com/science/article/pii/S1742287616300433. It is very interesting and makes me thinking about one thing.

Is it possible to manipulate file modify/access/change time metedata using C or any other language in Linux OS? I found method which is using touch command, but it creates file with specific tag value. I would like to find way to modify this metadata in existing one.

Emrick

look at man touch more carefully – Preclude

@IporSircer I've just found an answer. My question can be closed :) – Emrick

Krystian, this site is supposed to be a repository for knowledge in a Q&A format. If you've found an answer to your question, while this question may feel unnecessary to you now, you're still encouraged to write an answer for the benefit of any future readers. Unless you deem the question too trivial to answer or it already has a duplicate on the site, in which case you should flag it thusly. – Risser

Answer 1

Using touch command you can edit time metadata of files. Example:

touch -a -t 201611161200.10 file.txt

It will result in modifing access timestamp, and replace it with date 2016-11-16 12:00:10.000000000 To change 'Modify' date you should use flag -m

Emrick

Answer 2

I came across this thread and I had to share my findings (as mentioned this site is a repository for knowledge):

• "touch" is a command line application and in order to execute it (from c++ application) you need to run system() which is discouraged. more on touch: http://www.linfo.org/touch.html

• The programmatic way to set the access and modification timestamps of a file is using one of the following system calls: utime, utimes, futimes, futimens (simple internet search will give you the man page of them) i.e http://www.tin.org/bin/man.cgi?section=2&topic=utimensat

• Linux has 3 time stamps associated to a file:

  1. Access - the last time the file was read
  2. Modify - the last time the file was modified (content has been modified)
  3. Change - the last time meta data of the file was changed (e.g. permissions) extra reading here: https://unix.stackexchange.com/questions/2464/timestamp-modification-time-and-created-time-of-a-file/2465#2465?newreg=b4e0ee2ef0734b8792240c205e420c55

• It's relatively easy to modify the 'access' and 'modify' timestamps using the above commands, but modifying the change timestamp (last time permissions were changed) is harder. Thread on this here: Setting creation or change timestamps

Testudinal

See also lutimes() if you want to correctly handle symlinks. – Skillful

Answer 3

touch -c -m --date="2022-02-19 10:00" /path/to/your/file

Sims