fixed a lot of stuff

functions/findstr.fish

@@ -3,8 +3,14 @@ function findstr
         echo "Usage: findstr <search-string>"
         return 1
     end
+    if not command -q find
+        echo "findstr: 'find' is not installed."
+        return 1
+    end
+    if not command -q grep
+        echo "findstr: 'grep' is not installed."
+        return 1
+    end
 
-    set query $argv[1]
-
-    find . -type f -exec grep -Hn "$query" {} \;
+    find . -type f -exec grep -Hn "$argv[1]" {} \;
 end