In /usr/bin/xclip-copyfile line 8:
archive=`mktemp` || exit 1
        ^------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
archive=$(mktemp) || exit 1


In /usr/bin/xclip-copyfile line 15:
        filedir=`dirname "${file}"`
                ^-----------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
        filedir=$(dirname "${file}")


In /usr/bin/xclip-copyfile line 16:
        filename=`basename "${file}"`
                 ^------------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
        filename=$(basename "${file}")

For more information:
  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...