Script to set screen resolution by providing X and Y co-ordinates in RedHat

The goal is to provide resolution X and Y as arguments to the script ./res_set.sh 1920 1080 and gtf, xrandr --newmode and --addmode will be executed according to the script. #!/usr/bin/env bash if [ "$1" == "-h" ]; then echo "Usage: basename $0 [X co-ordinate] [Y co-ordinate]" exit 0 fi echo "X Co-ordinate"; echo $1; echo "Y Co-ordinate"; echo $2; echo "Are you sure? [Y/N]"; read input; if [ $input == "y" ]; then gtf $1 $2 60 > kar1.txt #To get modeline sed -n '3 p' kar1.txt > kar2.txt #Select Line 2 grep -o -E '["_x.0-9 ]+' kar2.txt > kar3.txt #Filter result wo_filter=$(perl -p -e 's/(?:_60.00)//g' kar3.txt | grep "\S"); filter=$(grep "\S" kar3.txt); fil_resolution=$(grep -o -P '(?<=").*(?=")' <<< $wo_filter) resolution=$(grep -o -P '(?<=").*(?=")' kar3.txt) echo "Filter: $filter"; echo "Wo_filter: $wo_filter"; echo "Resolution: $resolution"; echo "Filted_Resolution: $fil_resolution"; var=$(xrandr --newmode $wo_filter) xrandr --addmode default $fil_resolution #rm -v kar* else exit; fi This creates xrandr --newmode but fails to add the mode --addmode in the resolution list while using this script. I get xrandr:Cannot find mode. But it works and adds to the mode list if xrandr --newmode and --addmode commands are executed individually. This is the output of xrandr | tail My thoughts are : Are *$variables* are in different datatype and spoiling my result? How will I be able to verify the data type of variables here or in bash (does it matter)?