xrandr.sh

!/bin/bash
#If no argument is specified, ask for it and exit
if [[ -z "$@" ]];
then
    echo "An argument is needed to run this script. For instance..."
    echo ">./xrandr.sh 3840 2160 60"
    echo "will set a resolution of 4k @ 60 Hz."
    exit
else
    arg="$@"
    #Basic check to make sure argument number is valid. If not, display error and exit
    if [[ $(($(echo $arg | grep -o "\s" | wc --chars) / 2 )) -ne 2 ]];
    then
        echo "Invalid Parameters. You need to specify parameters in the format \"width height refreshRate\""
        echo "For example setResolution \"1920 1080 60\""
        exit
    fi
    
    #Save stuff in variables and then use xrandr with those variables
    modename=$(echo $arg | sed 's/\s/_/g')
    display=$(xrandr | grep -Po '.+(?=\sconnected)')
    if [[ "$(xrandr|grep $modename)" = "" ]];
    then
        xrandr --newmode $modename $(gtf $(echo $arg) | grep -oP '(?<="\s\s).+') &&
        xrandr --addmode $display $modename     
    fi
    xrandr --output $display --mode $modename

    #If no error occurred, display success message
    if [[ $? -eq 0 ]];
    then
        echo "Display changed successfully to $arg"
    fi
fi

<<COMMENT
#Manual steps with explanation ahead by @debloper
# First we need to get the modeline string for xrandr
# Luckily, the tool "gtf" will help you calculate it.
# All you have to do is to pass the resolution & the-
# refresh-rate as the command parameters:
gtf 1920 1080 60

# In this case, the horizontal resolution is 1920px the
# vertical resolution is 1080px & refresh-rate is 60Hz.
# IMPORTANT: BE SURE THE MONITOR SUPPORTS THE RESOLUTION

# Typically, it outputs a line starting with "Modeline"
# e.g. "1920x1080_60.00"  172.80  1920 2040 2248 2576  1080 1081 1084 1118  -HSync +Vsync
# Copy this entire string (except for the starting "Modeline")

# Now, use "xrandr" to make the system recognize a new
# display mode. Pass the copied string as the parameter
# to the --newmode option:
xrandr --newmode "1920x1080_60.00"  172.80  1920 2040 2248 2576  1080 1081 1084 1118  -HSync +Vsync

# Well, the string within the quotes is the nick/alias
# of the display mode - you can as well pass something
# as "MyAwesomeHDResolution". But, careful! :-|

# Then all you have to do is to add the new mode to the
# display you want to apply, like this:
xrandr --addmode VGA1 "1920x1080_60.00"

# VGA1 is the display name, it might differ for you.
# Run "xrandr" without any parameters to be sure.
# The last parameter is the mode-alias/name which
# you've set in the previous command (--newmode)

# It should add the new mode to the display & apply it.
# Usually unlikely, but if it doesn't apply automatically
# then force it with this command:
xrandr --output VGA1 --mode "1920x1080_60.00"

# That's it... Enjoy the new awesome high-res display!
COMMENT