elementary shell behavior: can kick off a foreground process and

handle signals

src/lex.rs

@@ -206,13 +206,20 @@ fn process(document: &String) -> Result<Box<Seg>, String> {
 }
 
 /* Returns true if token
- *   - is all alphanumeric except dash and underscore
- *
+ *   - is all alphanumeric except dash, question, and underscore
+ *   - equals is also allowed but only for shell command compatibility
  * else returns false
  */
 fn tok_is_symbol(token: &str) -> Option<String> {
     for t in token.chars() {
-        if !t.is_alphanumeric() && t != '-' && t != '_' && t != '?' {
+        if !t.is_alphanumeric() &&
+            t != '-' &&
+            t != '_' &&
+            t != '?' &&
+            t != '=' &&
+            t != '.' &&
+            t != '/'
+        {
             return None;
         }
     }