I'm trying to adapt a Steam Deck screen-rotation script for Wayland. The original script used xrandr, so I rewrote it to use kscreen-doctor:
#!/bin/bash
screen="eDP-1"
default_screen_orientation=8
screen_info=$(kscreen-doctor -o | grep "$screen" | awk '/Rotation/ {print $3}')
if [[ "$screen_info" -eq "$default_screen_orientation" ]]; then
kscreen-doctor output.eDP-1.rotation.right
else
kscreen-doctor output.eDP-1.rotation.none
fi
When I run the kscreen-doctor, grep, and awk pipeline directly in a terminal, it returns 8 as expected. However, when the same command runs inside the script, screen_info is empty or null. I'm new to Bash and would appreciate help finding the problem. Is there also a way to step through a Bash script similarly to stepping through an Excel formula?
2 Answers
Start by checking each stage of the pipeline separately instead of assigning everything at once. For example:
output=$(kscreen-doctor -o)
printf '%sn' "$output"
filtered=$(printf '%sn' "$output" | grep "$screen")
printf '%sn' "$filtered"
rotation=$(printf '%sn' "$filtered" | awk '/Rotation/ {print $3}')
printf 'rotation=[%s]n' "$rotation"
That will show exactly where the expected text disappears. Also quote variables when passing their contents to other commands. Bash tracing can help too: run the script with `bash -x script.sh`, or add `set -x` near the top. One detail worth checking is the option spelling: use `-o` if that is what kscreen-doctor expects, rather than `--o`.
Verify the output format before assuming that field 3 is the rotation value. Run `kscreen-doctor -o` by itself, then try the command without `awk` and inspect the exact line that contains `Rotation`. Formatting or a slightly different output in the script can make the pattern fail. You can also make the script stop on errors and show commands as they execute by adding `set -euxo pipefail` near the beginning. If the command works interactively but not from the script, compare the shell, PATH, and environment used to launch the script.
I wasn’t sure whether `--o` and `-o` were equivalent, so I’ll check that first. I’ll also inspect the raw output and confirm which field contains the value instead of relying on the terminal result alone.
That makes sense. The problem is with the value assigned to screen_info, not the if statement. I’ll split up the pipeline and print each intermediate result. Since the Deck only has one display, I may be able to simplify the command as well.