Switch Your Samsung M8 Monitor HDMI Inputs from the Terminal (No Remote Needed)

If you run two machines — a work laptop and a personal desktop — connected to a Samsung M8, you already know the pain: reach for the remote, navigate the OSD menu, switch source, repeat twenty times a day. Here's how to collapse that into a single terminal command using the SmartThings CLI.

The best part: this approach works identically on both macOS and Linux since it's Node.js-based.

How This Works

The Samsung M8 is a SmartThings-connected display. Samsung exposes a first-party CLI — @smartthings/cli — that can send commands to any registered SmartThings device, including input source switching on the M8. No hacking, no reverse engineering, no X11 tools.

What You Need

• Samsung M8 monitor connected to your SmartThings account
• Node.js (we'll use asdf for version management)
• SmartThings CLI installed globally via npm
• Your M8's SmartThings device ID

Step 1: Install Node.js via asdf

asdf works the same on macOS and Linux, which is why it's the cleanest approach here.

macOS:

brew install asdf

Linux (Ubuntu/Debian):

sudo apt install curl git
git clone https://github.com/asdf-vm/asdf.git ~/.asdf --branch v0.14.0
echo '. "$HOME/.asdf/asdf.sh"' >> ~/.zshrc
source ~/.zshrc

Then install Node.js:

asdf plugin add nodejs
asdf install nodejs 24.13.0
asdf global nodejs 24.13.0

Verify:

node --version   # v24.13.0

Step 2: Install the SmartThings CLI

npm install -g @smartthings/cli

Verify:

smartthings --version

Step 3: Authenticate with SmartThings

smartthings devices

This will open a browser and ask you to log in with your Samsung account. After authentication, it lists all your SmartThings devices.

Step 4: Find Your M8 Device ID

After authentication, smartthings devices outputs a table. Find your Samsung M8 and copy its device ID — it looks like a UUID:

┌────┬─────────────────┬──────────────────────────────────────┐
│ #  │ Label           │ Device ID                            │
├────┼─────────────────┼──────────────────────────────────────┤
│  1 │ Samsung M8      │ xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx │
└────┴─────────────────┴──────────────────────────────────────┘

Export it in your ~/.zshrc.local (keep it out of your dotfiles repo since it's device-specific):

export SMARTTHINGS_MONITOR_ID='xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'

Step 5: The Toggle Script

Create ~/dotfiles/scripts/monitor_input.sh:

#!/usr/bin/env bash
# Control Samsung M8 monitor input via SmartThings CLI
# Requires: smartthings CLI + SMARTTHINGS_MONITOR_ID env var set in ~/.zshrc.local

_smartthings_cmd() {
  local st_bin="$HOME/.asdf/installs/nodejs/24.13.0/bin/smartthings"
  if [[ -x "$st_bin" ]]; then
    "$st_bin" "$@"
  else
    command smartthings "$@"
  fi
}

_monitor_check() {
  if ! _smartthings_cmd --version &>/dev/null; then
    echo "smartthings CLI not found." >&2
    echo "Run: npm install -g @smartthings/cli" >&2
    return 1
  fi
  if [[ -z "$SMARTTHINGS_MONITOR_ID" ]]; then
    echo "SMARTTHINGS_MONITOR_ID is not set." >&2
    echo "Run: smartthings devices   → find your M8 device ID" >&2
    echo "Then add to ~/.zshrc.local:  export SMARTTHINGS_MONITOR_ID='<id>'" >&2
    return 1
  fi
}

monitor_hdmi1() {
  _monitor_check || return 1
  echo "Switching to HDMI 1..."
  _smartthings_cmd devices:commands "$SMARTTHINGS_MONITOR_ID" \
    'main:mediaInputSource:setInputSource("HDMI1")'
}

monitor_hdmi2() {
  _monitor_check || return 1
  echo "Switching to HDMI 2..."
  _smartthings_cmd devices:commands "$SMARTTHINGS_MONITOR_ID" \
    'main:mediaInputSource:setInputSource("HDMI2")'
}

monitor_toggle() {
  _monitor_check || return 1
  local current
  current=$(_smartthings_cmd devices:status "$SMARTTHINGS_MONITOR_ID" 2>/dev/null \
    | jq -r '.components.main."samsungvd.mediaInputSource".inputSource.value // empty')

  if [[ -z "$current" ]]; then
    echo "Could not read current input source." >&2
    return 1
  fi

  echo "Current input: $current"
  if [[ "$current" == "HDMI1" ]]; then
    monitor_hdmi2
  else
    monitor_hdmi1
  fi
}

# Allow running directly: ./monitor_input.sh [hdmi1|hdmi2|toggle]
case "${1:-}" in
  hdmi1)  monitor_hdmi1 ;;
  hdmi2)  monitor_hdmi2 ;;
  toggle) monitor_toggle ;;
  *)
    echo "Usage: $0 [hdmi1|hdmi2|toggle]"
    echo "  or source this file and call monitor_hdmi1 / monitor_hdmi2 / monitor_toggle"
    ;;
esac

A couple of things worth noting in _smartthings_cmd: it tries the asdf-managed binary path first, then falls back to whatever smartthings is on $PATH. This means the script works whether you're using asdf or a global npm install.

Step 6: Wire Up the Aliases

Create ~/dotfiles/zsh/aliases/monitor.sh:

# ── Samsung M8 Monitor Input (SmartThings) ──────────────────────────────────

if command -v smartthings &>/dev/null; then
  source "$HOME/dotfiles/scripts/monitor_input.sh" 2>/dev/null

  alias hdmi1='monitor_hdmi1'
  alias hdmi2='monitor_hdmi2'
  alias hdmi-toggle='monitor_toggle'
  alias t='monitor_toggle'
fi

Source it from your .zshrc:

source "$HOME/dotfiles/zsh/aliases/monitor.sh"

The command -v smartthings guard means the aliases are silently skipped on any machine that doesn't have the CLI installed — no errors, no noise.

Usage

hdmi1         # switch to HDMI 1 (machine A)
hdmi2         # switch to HDMI 2 (machine B)
hdmi-toggle   # toggle between whichever is active
t             # same as hdmi-toggle, just shorter

Run it directly without sourcing:

~/dotfiles/scripts/monitor_input.sh toggle
~/dotfiles/scripts/monitor_input.sh hdmi1

Workflow in Practice

My setup: work MacBook on HDMI 1, personal Linux desktop on HDMI 2. A single t in the terminal and the monitor switches — no remote, no OSD, no context switch. Since it goes through SmartThings rather than DDC/CI, it works over the network too, so you don't even need to be in the same session as the machine you're switching away from.

Troubleshooting

smartthings CLI not found — Make sure the npm global bin is on your $PATH. Check with npm bin -g and add it to your shell profile if missing.

SMARTTHINGS_MONITOR_ID is not set — Add the export to ~/.zshrc.local (not your dotfiles repo) and re-source your shell.

Could not read current input source — Run smartthings devices:status $SMARTTHINGS_MONITOR_ID manually to inspect the raw JSON. The capability key may differ slightly on older M8 firmware; look for mediaInputSource in the output.

Commands time out — The M8 needs to be on and connected to your Wi-Fi network. Wake it from standby first, or disable deep sleep in the monitor's power settings.

That's it. SmartThings CLI, one script, four aliases, zero remote-reaching.

Full script and aliases live in my dotfiles: github.com/abhsss96/dotfiles — see scripts/monitor_input.sh and zsh/aliases/monitor.sh.