JPEG File Extraction from stdin

      cat > 056.l
 
        /* JPEG file carver */
    
     #define echo ECHO
     #define jmp BEGIN
     int fileno(FILE *);
    
    xa "\xFF\xD8"
    xb "\xFF\xD9" 
    
    %s xa 
    %option noyywrap nounput noinput
    %%
    
    {xa} echo;jmp xa;
    <xa>{xb} echo;jmp 0;
    <xa>.|\n|\r echo;
    .|\n
    
    %%
    int main(){ yylex();exit(0) ;}
    
    ^D

    flex 056.l
    cc -static -o yy056 lex.yy.c