batch.sh

#!/bin/bash
FILENAME_IN="$1"
FILENAME_OUT="$1.new"
rm $FILENAME_OUT
while IFS='' read -r line || [[ -n "$line" ]]; do
LINE=$line
NEWLINE=''

if [[ $line == *"custom_viewport_width"* ]]
then
CUSTOM_VIEWPORT_WIDTH=$(echo "$line" | sed 's/custom_viewport_width = "\(.*\)"/\1/')
NEWLINE='custom_viewport_width = "'$((CUSTOM_VIEWPORT_WIDTH * 2/3))'"';
fi

if [[ $line == *"custom_viewport_height"* ]]
then
CUSTOM_VIEWPORT_HEIGHT=$(echo "$line" | sed 's/custom_viewport_height = "\(.*\)"/\1/')
NEWLINE='custom_viewport_height = "'$((CUSTOM_VIEWPORT_HEIGHT * 2/3))'"';
fi

if [[ $line == *"custom_viewport_x"* ]]
then
CUSTOM_VIEWPORT_X=$(echo "$line" | sed 's/custom_viewport_x = "\(.*\)"/\1/')
NEWLINE='custom_viewport_x = "'$((CUSTOM_VIEWPORT_X * 2/3))'"';
fi

if [[ $line == *"custom_viewport_y"* ]]
then
CUSTOM_VIEWPORT_Y=$(echo "$line" | sed 's/custom_viewport_y = "\(.*\)"/\1/')
NEWLINE='custom_viewport_y = "'$((CUSTOM_VIEWPORT_Y * 2/3))'"'
fi

if [[ $NEWLINE == "" ]]
then
NEWLINE=$LINE
fi
echo "$NEWLINE" >> $FILENAME_OUT
done < "$1"