Automatically detect when HDMI is plugged in

Question

Sometimes I connect my laptop to my TV over HDMI to have a bigger screen. Unfortunately, it doesn't automatically switch the audio output, so I have to do that myself every single time I plug or unplug it, with either of those two, to have the sound come from where I want it to come from.

• pacmd set-card-profile 0 output:hdmi-stereo-extra1
• pacmd set-card-profile 0 output:analog-stereo+input:analog-stereo

Is there any way to detect if HDMI is plugged in, or at least if a change has occurred? Thanks!

Linux Mint 18.2 Xfce x64, Asus P756U

Answer 1

I am using two different ways to determine if HDMI is plugged in:

a) Using xrandr
A simple xrandr will report your hdmi monitor as connected To use this in a script you can do something like:

hdmi_active=$(xrandr |grep ' connected' |grep 'HDMI' |awk '{print $1}')

Above will return the connected hdmi port (i.e HDMI-1) or will return nothing if no HDMI is connected.

You can then use something like

[[ ! -z "$hdmi_active" ]] && do_your_stuff 

z becomes true if $hdmi_active is not set . ! z reverts this behavior and returns true if hdmi_active has a value = hdmi is connected

b) Using the HDMI status file:

$ cat /sys/class/drm/card0/*HDMI*/status

This returns connected / disconnected for your hdmi ports:

$ cat /sys/class/drm/card0/*HDMI*/status
disconnected
disconnected

You can then test against that result with something like:

hdmi_active="$(cat /sys/class/drm/card0/*HDMI*/status |grep '^connected')" #Using ^ we avoind matching disconnected from the regex match, since ^ in an anchor to the beginning of the line
[[ ! -z "$hdmi_active" ]] && do_your_stuff #hdmi is active