While copying data from my old storage on a Linux computer to the new (linux-based) NAS, I accidentially failed with getting the properties (most important: the modify dates) along to the new location. I also continued to use/modify the files at the new location and hence, cannot just copy it all over again.

What I would like to do is a diff between files in the old vs. the new storage, and for those being identical, restore the properties from Linux storage to the NAS storage files.

Is there a clever way such as a script or a tool to do this? I could either run it on the Linux box or in worst case from a remote Windows computer.

Grateful for any suggestions. /Jon

  • You could run a cryptographic hash on the files (SHA1 maybe), compare both of each file's hashes and if identical touch -m the NAS file (with the appropriate date time settings). It would be a hack, but I think it would work. – Elliott Frisch Apr 24 '14 at 2:32
  • Hi Elliott, Thanks for the suggestion. Yes, I will probably have to spend a few hours to create a solution like this. I was hoping I could be lazy and make use of an already-existing tool for this but as a second option your idea is good. – Jon Apr 25 '14 at 5:44
up vote 0 down vote accepted

I just thought I'd better share the code i've come up with. While not being a bash programmer, there's a lot of knowledge available via Google so I believe this code will do the work for me. Basically what it does is:

  • Loop through all files and folders in the new location and for each:
    • check if the same file exist in the old location
      • If no, then write a log entry
      • If yes, does the timestamp (modify date) match?
        • Yes - nothing to do but write a log entry
        • No, timestamps does not match
          • Is it either a directory or is file content identical? Then reset timestamp to the timestamp of the file in the old location, and write a log entry
          • If file content differs, then the timestamps may do as well. Just write a log entry.


shopt -s globstar

LOGFILE=restoreDates_$(date "+%Y-%m-%d-%H%M%S").log


for f in "$NEWDIR"/** ; do
OLDFILE=$(sed -e "s/$NEWDIR/$OLDDIR/" <<< $f)

  # Does corresponding file exist in old directory?

  if [ -a "$OLDFILE" ] ; then

    # Do both files have the same modify date?
    if [ $(stat -c %Y "$f") -eq $(stat -c %Y "$OLDFILE") ] ; then
        echo "$OLDFILE already has same modify date/time as $f" >> $LOGFILE

        # Is this a directory?
        if [ -d "$f" ]; then
            echo "$f is a directory, modify timestamp will be reset to that of $OLDFILE; $(stat -c %y "$OLDFILE")" >> $LOGFILE
            touch -r "$OLDFILE" "$f"
            # Not a directory - Is old file equal to the new?
            if $(cmp --silent "$f" "$OLDFILE"); then
                # yes
                echo "$OLDFILE and $f are identic, modify timestamp will be reset to $(stat -c %y "$OLDFILE")" >> $LOGFILE
                touch -r "$OLDFILE" "$f"
            else # File has changed
                echo "$OLDFILE differs from $f , which must have changed" >> $LOGFILE
  else # File does not exist in old directory
    echo "$OLDFILE does not exist (but $f do)" >> $LOGFILE


Any comments on the code are welcome.

  • My apologies for above presentation of the code - I was not able to bring it all into the code box... – Jon May 27 '14 at 20:58

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