How to grep for the dollar symbol ($)?

Question

% cat temp
$$$ hello1
$$  hello2
    hello3
##  hello4
    hello5 $$$
% cat temp | grep \"$$$\"
Illegal variable name.
% cat temp | grep \"\\$\\$\\$\"
Variable name          


        

Answer 1

$ grep '\$\$\$' temp
$$$ hello1
hello5 $$$

There's a superflous 'cat' in your command.