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