How to set the record source from bash script?

[D.Dave]

When I want to record audio from line in, I have to open pavucontrol, go to Recording tab, click the dropdown menu and select Built-In Audio Analog Stereo (green underlined), because the default entry is **Monitor** of Built-In Audio Analog Stereo (red underlined)

First step:

Second step:

I would make a bash script to set Built-In Audio Analog Stereo, using pactl or pacmd; I thought that would be enough to execute pactl set-default-source alsa_input.pci-0000_00_1b.0.analog-stereo but doesn’t do nothing.
How can I achieve this need with a bash script?

[D.Dave]

I have found the solution which works as expected:

loopbackindex=$(pacmd list-source-outputs | tr '\n' '\r' | perl -pe 's/ *index: ([0-9]+).+?media\.name = "([^\r]+)"\r.+?(?=index:|$)/\2:\1\r/g' | tr '\r' '\n' | grep Loopback | cut -d ":" -f2)
pacmd move-source-output $loopbackindex alsa_input.pci-0000_00_1b.0.analog-stereo

[nikgnomic]

PulseAudio has an option to specify the source devices for module-loopback

If you are loading the loopback module with the BASH script

pactl load-module module-loopback source=alsa_input.pci-0000_00_1b.0.analog-stereo

If the module is loaded in a default.pa configuration file omit the pactl command

The pacmd commands can be a bit temperamental when used in BASH scripts and sometimes fail
some (but not all) pactl commands work better without the daemon

There is a workaround for using pacmd in scripts, if required

echo 'move-source-output $loopbackindex alsa_input.pci-0000_00_1b.0.analog-stereo' | pacmd