End-of-File Rules

The special rule `<<EOF>>' indicates actions which are to be taken when an end-of-file is encountered and yywrap returns non-zero (i.e., indicates no further files to process). The action must finish by doing one of four things:

• the special YY_NEW_FILE action, if `yyin' has been pointed at a new file to process;
• a return statement;
• the special yyterminate action;
• or switching to a new buffer using yy_switch_to_buffer as shown in the example above.

`<<EOF>>' rules may not be used with other patterns; they may only be qualified with a list of start conditions. If an unqualified `<<EOF>>' rule is given, it applies to all start conditions which do not already have `<<EOF>>' actions. To specify an `<<EOF>>' rule for only the initial start condition, use

<INITIAL><<EOF>>

These rules are useful for catching things like unclosed comments. An example:

%x quote
%%

... other rules for dealing with quotes ...

<quote><<EOF>>   {
         error( "unterminated quote" );
         yyterminate();
         }
<<EOF>>  {
         if ( *++filelist )
             {
             yyin = fopen( *filelist, "r" );
             YY_NEW_FILE;
             }
         else
            yyterminate();
         }