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artu-hnrq
Asked: 2019-08-25 12:26:39 +0800 CST

How to set a shortcut that alternate it's function conditionally?

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I want to set a unique hotkey to be able to alternate the system sound between analog and HDMI outputs. How can I do this?

This behavior could be observed in play shortcut (from org.gnome.settings-daemon.plugins.media-keys) that play and pause the media alternatively.

I could find answered here that the command to set the sound-output is pactl set-card-profile 0 output:[card-profile]

sound gnome customization shortcut-keys hdmi

1 Answers

  1. Best Answer

    Well, reading the topics that DK Bose and vanadium suggested and having done some more research to learning about bash script and Linux PulseAudio sound server, I came up with one solution:

    We need to save the following script in a file (preferably in /usr/local/bin/, as explained here), mark it as executable (by run chmod +x over it) and then assigned it to a keyboard shortcut (optionally as explained here).

    #!/bin/bash
sound_output=$(pacmd list-cards | grep "active")

if [[ $sound_output = *"analog-stereo"* ]]; then
  sound_output=hdmi-stereo
else
  sound_output=analog-stereo
fi

pactl set-card-profile 0 output:"$sound_output"
echo -e "PulseAudio sound server output set to $sound_output"

    Explaning:

    • #!/bin/bash ensures that the interpreter for this script is bash, enabling extended syntax such as [[ ]].
    • As cited here, the syntax $( ) is "command substitution". This runs a command and use it's output to compose the line action. This way we save the return of pacmd list-cards | grep "active" in sound_output variable.
    • As explained here, the use of * in the condition turn it into a substring check.
    • As answered here, pactl set-card-profile 0 output: [card-profile] is the command to switch the sound server output, as wished.
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