Question

I’m trying to create a script that will automatically backup a complete directory tree. I also want it to work for incremental backups. Basically, it wil work like this:

• If file is in both source and destination and they are different, source file will be copied
• If file is in both source and destination and they are the same, nothing will be copied
• If file is only in the source, source file will be copied
• If file is only in the destination, destination file will be deleted.

I’m still new to shell scripting and I’m not sure how I could implement this. Any ideas? Windows batch scripts would be better, but shell scripts that run on Cygwin are also fine.

Answer 1

For windows batch scripting xcopy (native to windows) or robocopy (a free download in windows) both work extremely well.

An example xcopy script (in a .bat file):

@echo off
:: /L = list only.
:: /v=Verify, /y=No prompting /s=subdirs /z=Network mode (supports bad)
:: /i=Tells xcopy dest is folder /f=Display names /d=Copy only changed

echo Backing up projects...
xcopy e:\projects h:\projects /V /Y /S /Z /I /F /D

It will even support orphaned files (if you delete something from your source you no longer need a copy in the backup). Xcopy is typically fine for your needs until you deal with sync between NTFS and Fat32 file systems – the later only has a 2 second resolution and problems with daily savings time so you occasionally run into issues: (a) on time change day you might not get a backup of a changed file – depends on change-regularity of course or you might get a backup of all files even though none have changed (b) because of time resolution some files may backup even though they haven’t changed.