Regular expression for a string literal in flex/le

Question

I'm experimenting to learn flex and would like to match string literals. My code currently looks like:

"\""([^\n\"\\]*(\\[.\n])*)*"\""        {/*matches string-literal*/;}

I've been struggling with variations for an hour or so and can't get it working the way it should. I'm essentially hoping to match a string literal that can't contain a new-line (unless it's escaped) and supports escaped characters.

I am probably just writing a poor regular expression or one incompatible with flex. Please advise!

Answer 1

An answer that arrives late but which can be useful for the next one who will need it:

\"(([^\"]|\\\")*[^\\])?\"

Answer 2

This is what we use in Zolang for single line string literals with embedded templates ${...}

\"(\$\{.*\}|\\.|[^\"\\])*\"

Answer 3

A string consists of a quote mark

"

followed by zero or more of either an escaped anything

\\.

or a non-quote character

[^"\\]

and finally a terminating quote

"

Put it all together, and you've got

\"(\\.|[^"\\])*\"

The delimiting quotes are escaped because they are Flex meta-characters.

Answer 4

How about using a start state...

int enter_dblquotes = 0;

%x DBLQUOTES
%%

\"  { BEGIN(DBLQUOTES); enter_dblquotes++; }

<DBLQUOTES>*\" 
{ 
   if (enter_dblquotes){
       handle_this_dblquotes(yytext); 
       BEGIN(INITIAL); /* revert back to normal */
       enter_dblquotes--; 
   } 
}
         ...more rules follow...

It was similar to that effect (flex uses %s or %x to indicate what state would be expected. When the flex input detects a quote, it switches to another state, then continues lexing until it reaches another quote, in which it reverts back to the normal state.

Answer 5

For a single line... you can use this:

\"([^\\\"]|\\.)*\"  {/*matches string-literal on a single line*/;}