system command pipes (sp)

src-3.0/GF/Command/Abstract.hs

@@ -20,6 +20,7 @@ data Option
 data Value
   = VId  Ident
   | VInt Integer
+  | VStr String
   deriving (Eq,Ord,Show)
 
 data Argument
@@ -38,6 +39,11 @@ valIntOpts flag def opts = fromInteger $ case valOpts flag (VInt def) opts of
   VInt v -> v
   _      -> def
 
+valStrOpts :: String -> String -> [Option] -> String
+valStrOpts flag def opts = case valOpts flag (VStr def) opts of
+  VStr v -> v
+  _      -> def
+
 valOpts :: String -> Value -> [Option] -> Value
 valOpts flag def opts = case lookup flag flags of
   Just v -> v