Avoid a crash when run without a controlling tty, which may happen in some container environments.

2 files changed, 14 insertions, 1 deletions

diff --git a/CHANGELOG b/CHANGELOG
index f16e1b1..81d07f2 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,7 @@
 debug-me (1.20190926) UNRELEASED; urgency=medium
 
+  * Avoid a crash when run without a controlling tty, which may happen
+    in some container environments.
   * Update to lts-13.29, support ghc 8.6.5, and aeson 1.4.
 
  -- Joey Hess <id@joeyh.name>  Thu, 26 Sep 2019 19:44:58 -0400
diff --git a/ControlWindow.hs b/ControlWindow.hs
index bd79d0f..29c81c9 100644
--- a/ControlWindow.hs
+++ b/ControlWindow.hs
@@ -98,9 +98,20 @@ type Response = String
 type PromptChan = TChan Prompt
 type ResponseChan = TChan Response
 
+-- | Get a name for the debug-me user. When possible this will be the
+-- actual username, but failing that, anything reasonable will do,
+-- since it's only ever displayed to the person they are communicating
+-- with.
+getUserName :: IO String
+getUserName = do
+	loginname <- try getLoginName :: IO (Either SomeException String)
+	case loginname of
+		Right n -> return n
+		Left _ -> return "user"
+
 collectOutput :: TMChan ControlOutput -> PromptChan -> ResponseChan -> IO ()
 collectOutput ochan promptchan responsechan = do
-	myusername <- fromString <$> getLoginName
+	myusername <- fromString <$> getUserName
 	loop myusername
   where
 	loop myusername = do