Articles, notes and random thoughts on Software Development and Technology
Per discussion here, if you have a v1.1 version of the Raspberry Pi 7″ touchscreen, you can vary the brightness by setting a value of 1 to 255 into the file /sys/class/backlight/rpi-backlight/brightness
Use sudo to echo values to a file, do:
sudo sh -c "echo 80 > /sys/class/backlight/rpi_backlight/brightness"
From this article, if you’re using one of the Wifi dongles on a Pi 1 or 2 (Pi3 has built in wifi), you can prevent the random dropouts during periods of inactivity by:
sudo nano /etc/modprobe.d/8192cu.conf
and then paste in and save this:
options 8192cu rtw_power_mgnt=0 rtw_enusbss=1 rtw_ips_mode=1
and then reboot.
Replacing values in files is incredibly easy with sed. Here’s some examples:
sed 's/match/replace/g' file.txt
Find match, replace with replace, globally (all matches), in file.txt
sed 's/match/replace/g' file.txt > file2.txt
Same as before, but write results to new file, file2.txt
sed -n 's/match/replace/p' file.txt
-n suppresses output of the results, but /p prints out just the matching patterns that are replaced.
sed -i.old 's/match/replace/g' file.txt
Replace matches in the input file with inline replace (-i), renaming original file file.txt.old and writing inline replace results to file.txt
Install scrot (if not already installed): sudo apt-get install scrot
To pick a window, run ‘scrot -s’ and then click on the window that you want to capture. Screenshot is saved in your home dir by default.