Restoring file properties but not the complete files, from backup

Question

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

Answer 1

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.

Code:

shopt -s globstar

NEWDIR="/home/jon"
OLDDIR="/tmp/jon_old"
LOGFILE=restoreDates_$(date "+%Y-%m-%d-%H%M%S").log

echo $LOGFILE > $LOGFILE

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
    else

        # 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"
        else
            # 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" >> $LOGFILE
            fi
        fi
    fi
  else # File does not exist in old directory
    echo "$OLDFILE does not exist (but $f do)" >> $LOGFILE
  fi

done;

Any comments on the code are welcome.