Ubuntu search keyword via grep in specified file,the short cut to capture selection screen shot in Ubuntu 20.04 is Ctrl+Shift+Alt+R to start take screenshot functions

grep -i -n -r 'keyword'  specifilefile

Here is the definition:
grep is function name to search a pattern in files
-i means ignore case
-n means output line number
-r search recursively


Copy from https://www.ivankristianto.com/howto-find-keyword-in-files-with-grep-in-ubuntu/

grep -i -n -r '6000000000' log.txt

 

1.Alt+Shift+Ctrl+R will start the screen capture function in Ubuntu 20.04.

2.Paste the captured selection screen as below