Configure Monitors with xrandr on Linux

You can use a simple shell script in your .xinitrc file (or a standalone script) to check if the HDMI monitor is connected using xrandr and then execute the appropriate commands based on the presence of the HDMI monitor. Here’s how you can do that:

1. Create the Display Configuration Script

#

You can write a small script to detect the connected displays and apply the correct settings. Here’s an example script:

#!/bin/sh

# Check if HDMI-1 is connected
if xrandr | grep "HDMI-1 connected"; then
    # If HDMI-1 is connected, set it to 1920x1080 and position it to the right of eDP-1
    xrandr --output HDMI-1 --mode 1920x1080 --right-of eDP-1 --primary
else
    # If HDMI-1 is not connected, set eDP-1 to 1366x768
    xrandr --output eDP-1 --mode 1366x768 --rate 60.00 --primary
fi

2. Using the Script in .xinitrc

#

You can place this script directly into your .xinitrc file before launching DWM. Here’s how the .xinitrc file would look:

#!/bin/sh

# Check display and configure
if xrandr | grep "HDMI-1 connected"; then
    xrandr --output HDMI-1 --mode 1920x1080 --right-of eDP-1 --primary
else
    xrandr --output eDP-1 --mode 1366x768 --rate 60.00 --primary
fi

# Start background programs (optional)
# For example, start nm-applet or picom:
# nm-applet &
# picom --config ~/.config/picom.conf &

# Start DWM
exec dwm

3. Making .xinitrc Executable

#

Once the script is set up in .xinitrc, make sure the .xinitrc file is executable:

chmod +x ~/.xinitrc

4. Explanation:

#

• Checking HDMI-1: The command xrandr | grep "HDMI-1 connected" checks whether HDMI-1 is connected to the system.
• Setting resolutions: If HDMI-1 is connected, it will set it to 1920x1080 and position it to the right of eDP-1 (your laptop screen). If HDMI-1 is not connected, it will set the laptop screen eDP-1 to 1366x768.
• exec dwm: This launches DWM after configuring the displays.

5. Optional: Putting the Display Script in a Separate File

#

If you prefer to keep the logic in a separate script (instead of directly in .xinitrc), you can create a script, for example, ~/.display.sh:

1. Create the script:

   nano ~/.display.sh

2. Paste the display setup script inside it:

   #!/bin/sh
   
   # Check if HDMI-1 is connected
   if xrandr | grep "HDMI-1 connected"; then
       xrandr --output HDMI-1 --mode 1920x1080 --right-of eDP-1 --primary
   else
       xrandr --output eDP-1 --mode 1366x768 --rate 60.00 --primary
   fi

3. Make the script executable:

   chmod +x ~/.display.sh

4. Modify your .xinitrc to call this script before launching DWM:

   #!/bin/sh
   
   # Run the display setup script
   ~/.display.sh
   
   # Start DWM
   exec dwm

6. Testing the Setup

#

After making these changes, you can test the configuration by logging out and running:

startx