Question

I use flex to work on a scanner to replace \" with "; and \\ with \.

so my code is like

%%
\\"    \";
\\\    \\;

but when I compile, I get an error message like missing quote.
I think it’s the right regular expression, did I get wrong or it’s something special with flex?

Answer 1

You should escape both the \ AND " character. In order to match \" you use \\\" not \\". To match \\ you use \\\\ not \\\.

Another thing is that flex matches a regexp and then execute the C code you placed in the associated action. Your example doesn’t look like correct flex statements.