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flex: How can I match text only at the end of a file?

 
 How can I match text only at the end of a file?
 ===============================================
 
 There is no way to write a rule which is "match this text, but only if
 it comes at the end of the file".  You can fake it, though, if you
 happen to have a character lying around that you don't allow in your
 input.  Then you redefine 'YY_INPUT' to call your own routine which, if
 it sees an 'EOF', returns the magic character first (and remembers to
 return a real 'EOF' next time it's called).  Then you could write:
 
      <COMMENT>(.|\n)*{EOF_CHAR}    /* saw comment at EOF */
 

Info Catalog flex: Can I build nested parsers that work with the same input file? flex: FAQ flex: How can I make REJECT cascade across start condition boundaries?