switch-audio-out.sh

#!/bin/bash
# Toggles between two audio outputs.
# Note: Only works with a maximum of two audio outputs.
# Note: `pacmd` does not report its exit code to Bash, and does not print errors to stderr. I don't know why not, but that's how it is. It's better to use `pactl` for one-off commands.

# What to do if there is an error.
switch_error(){
    echo "Error: $error"
    zenity --error \
        --title="$(basename "$0")" \
        --text="$error\n$(basename "$0") cancelled."
    exit 1
}

# The sink (output) that is not currently in use.
next_sink="$(pacmd list-sinks | fgrep -v '*' | grep 'index' | grep -Eo '[0-9]{1,10}')"

# Input to the sinks.
sink_inputs="$(pacmd list-sink-inputs | grep 'index' | grep -Eo '[0-9]{1,10}')"

# Preliminary checks.
# Exits if less than two audio outputs are detected.
if [[ -z "$next_sink" ]]; then
    error="Fewer than two audio outputs detected."
    switch_error
# Confirms there are not more than two audio sinks, by looking for a space in the sink listing.
elif echo "$next_sink" | grep -q ' '; then
    error="More than two audio outputs detected."
    switch_error
fi

# Moves any currently playing audio streams to the new sink.
for i in $sink_inputs; do
    move_sink_input="$(pactl move-sink-input "$i" "$next_sink")"
    if [[ -z "$move_sink_input" ]]; then
        echo 'Switched sink input '"$i"' onto sink '"$next_sink"
    else
        >&2 echo "Error: pactl: $move_sink_input"
        error="Could not move sink input."
        switch_error
    fi
done

# Changes the default sink.
set_default_sink="$(pactl set-default-sink "$next_sink")"
if [[ -z "$set_default_sink" ]]; then
    echo 'Switched default audio output to sink '"$next_sink"
else
    >&2 echo "Error: pactl: $set_default_sink"
    error="Could not switch default sink."
    switch_error
fi

# Finds info about the new sink.
sink_info="$(pacmd list-sinks | grep -A 1 '* index')"

# Reports the name of the new sink.
if [[ "$sink_info" == *"Logitech_Wireless_Headset"* ]]; then
    sink_name="Logitech wireless headset"
elif [[ "$sink_info" == *"pci-0000_00_1b.0.analog-stereo"* ]]; then
    sink_name="built-in audio"
else
    sink_name="$(echo "$sink_info" | grep 'name' | cut -d'<' -f2 | cut -d'>' -f1)"
fi

# Shows more info in terminal.
echo 'Audio output now '"$sink_name"

# Shows a notification.
if [[ -n "$sink_inputs" ]]; then
    notify_sink_inputs="\nMoved currently playing audio streams."
fi
killall notify-osd
notify-send "Audio output" 'Switched to '"$sink_name.$notify_sink_inputs"