How do I match empty lines with Flex?

Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid>
Fri, 4 Oct 2019 22:01:48 +0800

          From comp.compilers

Related articles
How do I match empty lines with Flex? johann@myrkraverk.invalid (Johann 'Myrkraverk' Oskarsson) (2019-10-04)
Re: How do I match empty lines with Flex? 847-115-0292@kylheku.com (Kaz Kylheku) (2019-10-04)
Re: How do I match empty lines with Flex? johann@myrkraverk.invalid (Johann 'Myrkraverk' Oskarsson) (2019-10-05)
| List of all articles for this month |

From: Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid>
Newsgroups: comp.compilers
Date: Fri, 4 Oct 2019 22:01:48 +0800
Organization: Easynews - www.easynews.com
Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="21086"; mail-complaints-to="abuse@iecc.com"
Keywords: lex, question, comment
Posted-Date: 04 Oct 2019 11:29:50 EDT
Content-Language: en-GB

Dear comp.compilers,


The following program matches lines in a text file, but ignores empty
lines. Is there any way I can alter it so it returns something on empty
lines?


Is there a reason .* doesn't match zero characters in this case?


%option noyywrap noinput nounput


%{
#include <stdio.h>


          char *yylval;


%}




%%


..* { yylval = yytext; return 1; }
\n { yylineno += 1; }
<<EOF>> { return 0; }


%%


int main( int argc, char *argv[] )
{
          if ( argc > 1 ) {
                  yyin = fopen( argv[ 1 ], "r" );


                  while ( yylex() ) {
                          printf( "%d: %s\n", yylineno, yylval );


                  }
          }


          return 0;
}


--
Johann | email: invalid -> com | www.myrkraverk.com/blog/
I'm not from the Internet, I just work there. | twitter: @myrkraverk
[Flex never matches an empty string.
I expect a pattern like ^\n would do what you want. -John]


Post a followup to this message

Return to the comp.compilers page.
Search the comp.compilers archives again.