Monitor Switch

A simple Linux CLI app for switching inputs on DDC/CI-supported monitors. It uses ddcutil and includes an interactive ncurses menu.

Requirements

• Linux
• ddcutil
• DDC/CI enabled in the monitor settings
• Access to /dev/i2c-*
• CMake 3.16+, a C++17 compiler, and ncurses development files to build

Install ddcutil with your package manager:

# Arch Linux
sudo pacman -S ddcutil

# Debian / Ubuntu
sudo apt install ddcutil

# Fedora
sudo dnf install ddcutil

Load the I2C module and grant your user device access if needed:

sudo modprobe i2c-dev
sudo usermod -aG i2c "$USER"

Log out and back in after changing groups.

Build

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build
ctest --test-dir build --output-on-failure
sudo cmake --install build

Usage

monitor-switch                 # interactive menu
monitor-switch dp-1            # DisplayPort 1
monitor-switch dp-2            # DisplayPort 2 (standard VCP value 0x10)
monitor-switch hdmi-1          # HDMI 1
monitor-switch hdmi-2          # HDMI 2
monitor-switch usb-c           # USB-C
monitor-switch auto            # automatic input selection
monitor-switch --current       # show current input
monitor-switch --detect        # list detected monitors
monitor-switch --doctor        # diagnose setup problems
monitor-switch --list          # list known input values

When one compatible monitor is detected, it is selected automatically. With multiple monitors, use the interactive menu or select one explicitly:

monitor-switch dp-1 --display 2
monitor-switch dp-1 --bus 4
monitor-switch dp-1 --serial ABC123
monitor-switch dp-1 --monitor "Display Model"

Input-source values vary between monitor models. Use monitor-switch --list for the built-in mappings or pass a raw VCP value such as 0x0f.

The interactive menu asks the selected monitor for its advertised VCP 0x60 values and shows only those inputs when possible. Monitor capability strings are not always accurate, so the menu falls back to the built-in mappings and raw values remain available.

Run ddcutil detect if a monitor does not appear.