[Bash] Bash Detect Moniter

[abbatrombone]

I am trying to find a way to use a bash script to detect if a certain monitor is connected and then have it launch btop (a hardware monitoring program) onto that monitor. I am not sure what information i need to capture in order for the script to see it is open. Would anyone know how to do hardware detection?

[steve_v]

The first things that spring to mind for checking what is connected are 'xrandr --listmonitors', '/sys/class/drm/card0-[output]/status', and '/sys/class/drm/card0-[output]/edid' (possibly useful for matching a specific monitor rather than the output port).
It might also be possible to get this triggered from udev, but testing that is more scewing about than I'm up for right now TBH.
Alternatively, this little daemon might be of interest, though I haven't tried it myself.

[abbatrombone]

Hello,

Thanks I ran that first command and i found the monitor:

XWAYLAND2 1024/150x600/90+0+480 XWAYLAND2

the other commands did just said that directory didn't exist
Its easy to tell which one it is because its for raspberry pies.

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case "${SRANDRD_OUTPUT} ${SRANDRD_EVENT}" in
  "DVI-0 connected") xrandr --output DVI-0 --auto --right-of LVDS;;
  "VGA-0 connected") xrandr --output VGA-0 --auto --left-of LVDS;;
esac

This does seem promising I would just need to figure out if HDMI is just HDMI like VGA is VGA, as well as, if i need to mess with DVI

[steve_v]

XWAYLAND2 1024/150x600/90+0+480 XWAYLAND2

Ahh, that newfangled wayand thing I see. There's probably some wayland-specific way to get what you're after as well, but I don't use it so I don't know what it might be.

the other commands did just said that directory didn't exist

Yeah, those sysfs nodes are dependent on the GPU driver. They're probably a more efficient way to get the information since it's provided by the driver/kernel rather than querying X, but depending on the driver in use you may not have them or they may be under different directories/names.

In any case, if xrandr works, xrandr works.

[abbatrombone]

I've been tinkering with this for a little bit and i'm new to xrandr and I havent been able to get any of the statements to work. I figured by taking a case statement where if the output to the monitor exists then do this command would be what i need. However, whenever i try to test any of the out put logic by itself I just get not found; ignoring.

Here is an example basic test code that should work based on what im seeing online Xrandr Guide

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xrandr --output VGA1-0

Would you be able to help?

[abbatrombone]

Hello after months of googling i have made progress!

This code kept failing and for the life of me i couldnt figure out why it didnt find the connection.

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xrandr --output DVI-0 --auto --right-of LVDS;;

The reason is because my system doesn't use DVI or VGA it uses XWAYLAND.

Im at a new error now, which i am not sure how to figure out it cant find LVDS does anyone know what wayland uses for this?

[CwF]

LVDS is essentially the lower level interface every gpu and display has. If exposed in software then there is a physical connection inside a laptop or embedded system where this gpu and display connection is inches apart and connected directly. It is a display type without and external connector. DP, HDMI, and VGA are then little sections or daughter boards of circuitry that convert this LVDS signal into another type of signal suitable for longer connections to a display using a cable. Within the display there is then another little batch of circuits that convert this signal back into LVDS and wired to the display.

That's all hardware details, Wayland, or it's fuller featured and experienced grandfather X, are software ensembles called a 'display server'.

The outputs LVDS, DP, HDMI, VGA all perform the same function as far as wayland is concerned.

[abbatrombone]

I knew cables had daughter boards in them but never knew what it was for or did, that was very good information and glad you provided it.

I am unsure however of how to troubleshoot my issue then. It cant fight the output

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xrandr --output XWAYLAND8 --auto --left-of VGA

I tried VGA, DP, HDMI, and LVDS none were detected (both left and right). There has to be an output being i can see the display and interact with it. xrandr -q tells me its connected but does not tell me how. Do you know how to find the output at all?