Download with Wget only if new version

Good morning, I have a custom software that updates with a custom script.sh. Part of the file goes something like this:

if [[ $software == A ]]
  then
    echo "downloading package..."
    rm -rf test.zip >> SoftwareUpdate.log
    wget --user admin --password "test" https://update.example.com/software/test.zip >> SoftwareUpdate.log
    if test -f test.zip
     then
       echo "Performing Backup of Old software"
       zip -r backup/test-$now.zip /var/www/html/* >> SoftwareUpdate.log
       echo "Clearing out old software from folder html"
       rm -rf software/* >> SoftwareUpdate.log
       echo "Unziping new software"
       unzip test.zip -d software  >> SoftwareUpdate.log
       echo "Overwriting / Applying update ..."
       yes | cp -rf software/* /var/www/html/ >> SoftwareUpdate.log
       echo "Changing permissions"
       chown -R www-data /var/www/html/* >> SoftwareUpdate.log
      else
       echo "test.zip doesn't exist, please insure that update is available and try again"
     fi

What I would like to do is have versions in name file, For example: test_1239.zip or test_1531.zip The software should check if the version available to wget is newer than the last one he downloaded, and proceed if that is true.

So scenario If online version = test_1531.zip and last downloaded version = test_1239.zip 1531 is larger than 1239 then proceed with download and update. Thank you

Solution 1:

Save the "Last-Modified" header contents from the last test.zip you downloaded, and add a "If-Modified-Since" header to your next wget request using the date string you received.

The server will answer with a 304 if there's no test.zip more recent.

As an alternative, you could leave test.zip in the current directory, then using wget with the timestamping option (-N), will only download test.zip if the server has a newer version. Check the output of wget, if it contains "304 Not Modified" and "Omitting download", you know you may skip the version control.