SHELL

grep lines after match

$ grep -A1 text

-AX tells grep to display 'X' amount of lines after line of match. 
Use -BX to do the same but before.

grep line after match

Include -A flag to add lines after match and -B flag to add lines before
grep match -A 3	#display match line and 3 after lines
grep match -B 2 #display match line and 2 lines before

grep all lines until match

sed -n -e '/Word A/,/Word D/ p' file

grep lines before and after

# display 3 lines before and after matchline
rg -C 3 "keyword"