unix tool wc written in lex

wc.l

%{
    int nchar, nword, nline;
%}

%%
\n          { nline++; nchar++ ;}
[^ \t\n]+   { nword++; nchar += yyleng; }
.           { nchar++; }
%%

int main(int argc, char *argv[]) {
    yyin = fopen(argv[1], "r");
    yylex();
    printf("%d\t%d\t%d\n", nchar, nword, nline);
    fclose(yyin);
}