<p><pre><code> # make config parser (yy018)
# source code for 018.l is below
flex -8iCrfa 018.l;
cc -Wall -std=c89 -static -o yy018 lex.yy.c;
# create a config (ua.txt)
# format is name: "value"
# no indent, must be left-justified
cat > ua.txt
httpVersion="1.0"
Host: ""
Connection: "close"
User-Agent: "CERN-LineMode/2.15 libwww/2.17b3"
^D
save as "018.l"
int setenv (const char *, const char *, int);
int fileno(FILE *);
#define jmp (yy_start) = 1 + 2 *
#define X(x) fputs(x,stdout)
#define Y(x,y) fprintf(stdout,x,y)
#define Y2(x,y) fprintf(stderr,x,y)
int xxyy()
{
setenv("value",yytext,1);
Y("\40\40\40if(0==setenv(\"%s\",",getenv("name"));
Y("%s,0))",getenv("value"));
Y("Y(\"%s: %%s\\r\\n\",",getenv("name"));
Y("getenv(\"%s\"));\n",getenv("name"));
return 0;
}
int lineno=1;
%option noinput nounput noyywrap
%s xa xc
%%
\n lineno++;
^[\40\11]+ {
Y2("yy018: error: remove %d ",yyleng);
Y2("leading spaces/tabs from line %d\n",lineno);
yyterminate();
}
^"Host"[: ] setenv("name","Host",1);jmp xc;
^[^\40\11\":\n]* setenv("name",yytext,1);jmp xa;
<xa>[\"][^\"]*[\"] {
if(yyleng>2)xxyy();
else if(yyleng==2&&yytext[0]=='\"'&&yytext[1]=='\"') {
setenv("value",yytext,1);
Y("\40\40\40if(getenv(\"%s\"))",getenv("name"));
Y("Y(\"%s: %%s\\r\\n\",",getenv("name"));
Y("getenv(\"%s\"));\n",getenv("name"));
};}
<xc>[\"][^\"]*[\"] xxyy();
\n|.
%%
int main(){yylex();return 0;}</code></pre>