: "Optional items
Question mark in colou?r means u optional
It is placed after the character that is optional
Grouping for optional, is one of the main uses of parantheses
A='color colour colur colou semicolon'
B='4 4th 4th?'echo$A | grep 'colou?r' -o -E | tee result.txt
echo$B | grep '4(th)?' -o -E | tee result.txt -a