Unable to edit hosts or pf.conf file using objective c

I am trying to edit hosts file. But it gives error "sudo: no tty present and no askpass program specified". I have tried but its not working. Please help if anyone know. Thank You.

NSMutableString* pfConf = [NSMutableString stringWithContentsOfFile: @"/private/etc/pf.conf" encoding: NSUTF8StringEncoding error: nil];
if ([pfConf rangeOfString: @"/private/etc/pf.anchors/org.eyebeam"].location == NSNotFound) {
    [pfConf appendString: @"n"
     "anchor "org.eyebeam"n"
     "load anchor "org.eyebeam" from "/private/etc/pf.anchors/org.eyebeam"n"];
}
[pfConf writeToFile: @"/private/etc/pf.conf" atomically: true encoding: NSUTF8StringEncoding error: nil];