Changing a file's "Date Created" and "Last Modified" attributes to another file's

  • I'm using merge cap to create a merge pcap file from 15 files. For the merged file, I have changed the name to that of the first of the 15 files. But I would also like to change the merged file's attributes like "Date Created" and "Last Modified" to that of the first one. Is there anyway to do this?

    FILES_dcn=($(find  $dir_dcn -maxdepth 1 -type f -name "*.pcap"  -print0 | xargs -0 ls -lt | tail -15 | awk '{print $9}'))
    TAG1_dcn=$(basename "${FILES_dcn[14]}" | sed 's/.pcap//')
    mergecap -w  "${dir_dcn}"/merge_dcn.pcap "${FILES_dcn[@]}"
    mv  "${dir_dcn}"/merge_dcn.pcap  "${dir_dcn}"/"${TAG1_dcn}".pcap
    

    I try to access the merged files over a samba server (Ubuntu). So that an extractor function can access auto extract the files to D folder. But as the created date will be changed for the merged file the extraction fails. Is there anyway to fix this?

  • slm

    slm Correct answer

    7 years ago

    You can use the touch command along with the -r switch to apply another file's attributes to a file.

    NOTE: There is no such thing as creation date in Unix, there are only access, modify, and change. See this U&L Q&A titled: get age of given file for further details.

    $ touch -r goldenfile newfile
    

    Example

    For example purposes here's a goldenfile that was created with some arbitrary timestamp.

    $ touch -d 20120101 goldenfile
    $ ls -l goldenfile 
    -rw-rw-r--. 1 saml saml 0 Jan  1  2012 goldenfile
    

    Now I make some new file:

    $ touch newfile
    $ ls -l newfile 
    -rw-rw-r--. 1 saml saml 0 Mar  7 09:06 newfile
    

    Now apply goldenfile's attributes to newfile.

    $ touch -r goldenfile newfile 
    $ ls -l goldenfile newfile
    -rw-rw-r--. 1 saml saml 0 Jan  1  2012 newfile
    -rw-rw-r--. 1 saml saml 0 Jan  1  2012 goldenfile
    

    Now newfile has the same attributes.

    Modify via Samba

    I just confirmed that I'm able to do this using my Fedora 19 laptop which includes version 1.16.3-2 connected to a Thecus N12000 NAS (uses a modified version of CentOS 5.x).

    I was able to touch a file as I mentioned above and it worked as I described. Your issue is likely a problem with the either the mounting options being used, which may be omitting the tracking of certain time attributes, or perhaps it's related to one of these bugs:

    @JishnuUNair - can you check to see how the Samba share is being mounted (with what options)? You can typically get these from the `mount` command and then look for the share you're accessing. Just a guess but it's likely being mounted use gvfs as a FUSE filesystem.

    A lot of filesystems now support a file creation time. For ext4, you can view/change it through `debugfs` (although this needs root privileges and is no use here). See this question - http://unix.stackexchange.com/questions/50177/birth-is-empty-on-ext4

    @Graeme - yes I'd just referenced a similar method using stap: http://unix.stackexchange.com/questions/91197/how-to-find-creation-date-of-file/92748#92748 in the chatroom.

    While Linux does not support a creation time, a Samba share can. Depending on how you set it up (and xattr support in the file system), Samba has the ability to store some time stamps in Linux xattrs. That means it may be able to do things that the underlying file system cannot - like report a valid (modifiable) creation time. Sorry, I didn't find any good links to how this works.

    Actually most Linux file systems (eg. ext4) now support creation date, and Linux 4.11 will have a `statx()` call to retrieve it. Finally.

License under CC-BY-SA with attribution


Content dated before 6/26/2020 9:53 AM