LEX Program to Selects only lines that end or begin with the letter 'a'. Deletes everything else.

%{
/* Selects only lines that end or
   begin with the letter 'a'.
   Deletes everything else.
*/
#include <stdio.h>
%}
ends_with_a     .*a\n
begins_with_a   a.*\n
%%
{ends_with_a} ECHO;
{begins_with_a} ECHO;
.*\n ;
%%
main() { yylex(); return 0; }