How to make YY_INPUT point to a string rather than stdin in Lex & Yacc (Solaris)

Question

I want my yylex() to parse a string rather than a file or standard input. How can I do it with the Lex and Yacc provided with Solaris?

Answer 1

Here is something that should work with any implementation, although risky by using popen.

$ cat a.l
%%
"abc" {printf("got ABC\n");}
"def" {printf("got DEF\n");}
. {printf("got [%s]\n", yytext);}
%%
int main(int argc, char **argv)
{
    return(lex("abcdefxyz"));
}
lex(char *s)
{
    FILE *fp;
    char *cmd;
    cmd=malloc(strlen(s)+16);
    sprintf(cmd, "/bin/echo %s", s); // major vulnerability here ...
    fp=popen(cmd, "r");
    dup2(fileno(fp), 0);
    return(yylex());
}
yywrap()
{
    exit(0);
}
$ ./a
got ABC
got DEF
got [x]
got [y]
got [z]