Managing Multiple Monitors on Linux Mint with xrandr

Craig Wilson

2024-10-02

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Managing Multiple Monitors on Linux Mint with `xrandr`

When using a Linux laptop with an external docking station, managing multiple monitors effectively can be challenging. If you often connect and disconnect external monitors, you may want a quick way to toggle between using only your laptop display and activating external monitors.

In this post, I will show a custom script using xrandr to streamline the process. The script has been tested in Linux Mint 22, which is running X11.

Step 1: Understanding `xrandr` for Monitor Management

xrandr is a command-line utility for configuring and managing monitors in Linux. You can list connected displays, adjust resolutions, and enable or disable monitors. Here are a few quick commands to get started:

List all connected monitors:
```
xrandr
```

Enable or disable specific monitors:

xrandr --output HDMI-1 --off   # Turn off an external display (HDMI-1)
xrandr --output eDP-1 --auto   # Enable the internal laptop display (eDP-1)

Step 2: Setting Up the Script

To simplify switching between display modes, we can write a script that:

Detects connected monitors
Allows toggling between using only the internal display or activating external monitors
Logs actions for easy troubleshooting

Below is our script, toggle_displays.sh. You can copy it to your local machine and customize it as needed.

The `toggle_displays.sh` Script

#!/bin/bash

# toggle_displays.sh - A script to toggle between internal-only and external display setups using xrandr
# Version: 1.0
# Author: Craig
# Published: 2024-10-02
# Description: This script detects internal and external displays, enables only the internal display, or enables external displays when requested.
# Usage: ./toggle_displays.sh {internal|external} [--log]
# Example: ./toggle_displays.sh internal --log
# Versioning
# 
# 1.0 - Release
#

SCRIPT_VERSION="1.4"

# Default log file path
LOG_FILE="toggle_displays.log"
LOG_TO_FILE=false
MODE=""

# Parse command-line arguments
for arg in "$@"; do
    case $arg in
        --log)
            LOG_TO_FILE=true
            shift # Remove --log from processing
            ;;
        internal|external)
            MODE=$arg
            shift # Remove mode from processing
            ;;
        *)
            echo "Invalid option: $arg"
            echo "Usage: $0 {internal|external} [--log]"
            exit 1
            ;;
    esac
done

# Validate that MODE is set (either "internal" or "external")
if [ -z "$MODE" ]; then
    echo "Missing mode. Usage: $0 {internal|external} [--log]"
    exit 1
fi

# Log function to output to console and optionally to a log file
log() {
    if $LOG_TO_FILE; then
        echo "$(date +'%Y-%m-%d %H:%M:%S') - $1" | tee -a "$LOG_FILE"
    else
        echo "$(date +'%Y-%m-%d %H:%M:%S') - $1"
    fi
}

# Log the start of the script and version
log "Starting toggle_displays.sh - Version $SCRIPT_VERSION"

# Log the initial DISPLAY and XAUTHORITY exports
log "Initial DISPLAY value: $DISPLAY"
log "Initial XAUTHORITY value: $XAUTHORITY"

# Check if the script is being run over SSH and set DISPLAY and XAUTHORITY if necessary
if [ -n "$SSH_CONNECTION" ]; then
    export DISPLAY=:0
    export XAUTHORITY=/home/$USER/.Xauthority
    log "Detected SSH session. DISPLAY set to $DISPLAY"
    log "XAUTHORITY set to $XAUTHORITY"
fi

# Automatically detect the internal and external displays
INTERNAL_DISPLAY=$(xrandr | grep " connected primary" | awk '{ print $1 }')
EXTERNAL_DISPLAYS=$(xrandr | grep " connected" | grep -v "$INTERNAL_DISPLAY" | awk '{ print $1 }')

# Log detected displays
log "Detected internal display: $INTERNAL_DISPLAY"
log "Detected external displays: $EXTERNAL_DISPLAYS"

# Function to use only the internal display
use_internal_only() {
    log "Switching to internal display only..."
    for display in $EXTERNAL_DISPLAYS; do
        log "Disabling external display: $display"
        xrandr --output "$display" --off
    done
    xrandr --output "$INTERNAL_DISPLAY" --auto
    log "Switched to internal display only."
}

# Function to enable external displays
enable_external_displays() {
    log "Enabling external displays..."
    xrandr --output "$INTERNAL_DISPLAY" --auto
    for display in $EXTERNAL_DISPLAYS; do
        log "Enabling external display: $display"
        xrandr --output "$display" --auto --right-of "$INTERNAL_DISPLAY"
    done
    log "Enabled external displays."
}

# Execute the corresponding function based on MODE
if [ "$MODE" == "internal" ]; then
    use_internal_only
elif [ "$MODE" == "external" ]; then
    enable_external_displays
fi

# Log the end of the script execution
log "Completed toggle_displays.sh - Version $SCRIPT_VERSION"

How to Use the Script

Save the Script: Copy the script above into a file called toggle_displays.sh.
Make It Executable: Run the following command to make the script executable:
```
chmod +x toggle_displays.sh
```
Run the Script:
- To use only the internal display:
```
./toggle_displays.sh internal
```
- To enable external displays:
```
./toggle_displays.sh external
```
Enable Logging: Add the --log option to enable logging to a file. For example:
```
./toggle_displays.sh external --log
```

The script will create a log file (toggle_displays.log) in the same directory if logging is enabled. This log file will capture each action the script takes, including which displays are enabled or disabled.

Conclusion

With this script, you now have a way to switch between using only your laptop display and enabling external monitors.