ENH dynamically grab wifi interface in xmobar

bin/xmobar.hs

@@ -13,10 +13,16 @@ module Main (main) where
 
 import           Control.Monad                       (filterM)
 
+import           Data.Either
 import           Data.List
+import           Data.Maybe
 
 import           DBus
 
+import           System.Directory
+import           System.FilePath.Posix
+import           System.IO.Error
+
 import           Xmobar.Plugins.Bluetooth
 import           Xmobar.Plugins.Device
 import           Xmobar.Plugins.IntelBacklight
@@ -83,52 +89,66 @@ filterSpecs = filterM (maybe (return True) exists . csDepends)
   where
     exists DBusDepends { ddBus = b, ddPath = p, ddSys = s } = pathExists s b p
 
-myCommands :: BarRegions
-myCommands = BarRegions
-  { brLeft =
-    [ CmdSpec
-      { csAlias = "UnsafeStdinReader"
-      , csDepends = Nothing
-      , csRunnable = Run UnsafeStdinReader
-      }
-    ]
+sysfsNet :: FilePath
+sysfsNet = "/sys/class/net"
 
-  , brCenter = []
-
-  , brRight =
-    [ CmdSpec
-      { csAlias = "wlp0s20f3wi"
+wirelessCmd :: String -> CmdSpec
+wirelessCmd interface = CmdSpec
+  { csAlias = interface ++ "wi"
   , csDepends = Nothing
   , csRunnable = Run
-        $ Wireless "wlp0s20f3"
+    $ Wireless interface
     [ "-t", "<qualityipat><essid>"
     , "--"
     , "--quality-icon-pattern", "<icon=wifi_%%.xpm/>"
     ] 5
   }
 
-    , CmdSpec
+getWireless :: IO (Maybe CmdSpec)
+getWireless = do
+  r <- tryIOError (listDirectory sysfsNet)
+  ns <- filterM hasWireless $ fromRight [] r
+  return $ case ns of
+    [n] -> Just $ wirelessCmd n
+    _   -> Nothing
+  where
+    hasWireless p = doesPathExist $ sysfsNet </> p </> "wireless"
+
+myCommands :: IO BarRegions
+myCommands = do
+  wirelessSpec <- getWireless
+  let left =
+        [ CmdSpec
+          { csAlias = "UnsafeStdinReader"
+          , csDepends = Nothing
+          , csRunnable = Run UnsafeStdinReader
+          }
+        ]
+  let right =
+        [ wirelessSpec
+
+        , Just $ CmdSpec
           { csAlias = "enp7s0f1"
           , csDepends = Just $ sysDepends devBus devPath
           , csRunnable = Run
             $ Device ("enp7s0f1", "<fn=2>\xf0e8</fn>", T.fgColor, T.backdropFgColor) 5
           }
 
-    , CmdSpec
+        , Just $ CmdSpec
           { csAlias = vpnAlias
           , csDepends = Just $ sysDepends vpnBus vpnPath
           , csRunnable = Run
             $ VPN ("<fn=2>\xf023</fn>", T.fgColor, T.backdropFgColor) 5
           }
 
-    , CmdSpec
+        , Just $ CmdSpec
           { csAlias = btAlias
           , csDepends = Just $ sysDepends btBus btPath
           , csRunnable = Run
             $ Bluetooth ("<fn=2>\xf293</fn>", T.fgColor, T.backdropFgColor) 5
           }
 
-    , CmdSpec
+        , Just $ CmdSpec
           { csAlias = "alsa:default:Master"
           , csDepends = Nothing
           , csRunnable = Run
@@ -142,7 +162,7 @@ myCommands = BarRegions
             ]
           }
 
-    , CmdSpec
+        , Just $ CmdSpec
           { csAlias = "battery"
           , csDepends = Nothing
           , csRunnable = Run
@@ -161,20 +181,20 @@ myCommands = BarRegions
             ] 50
           }
 
-    , CmdSpec
+        , Just $ CmdSpec
           { csAlias = "intelbacklight"
           , csDepends = Just $ sesDepends xmonadBus blPath
           , csRunnable = Run $ IntelBacklight "<fn=1>\xf185</fn>"
           }
 
-    , CmdSpec
+        , Just $ CmdSpec
           { csAlias = ssAlias
           , csDepends = Just $ sesDepends xmonadBus ssPath
           , csRunnable = Run
             $ Screensaver ("<fn=1>\xf254</fn>", T.fgColor, T.backdropFgColor)
           }
 
-    , CmdSpec
+        , Just $ CmdSpec
           { csAlias = "locks"
           , csDepends = Nothing
           , csRunnable = Run
@@ -189,12 +209,16 @@ myCommands = BarRegions
             ]
           }
 
-    , CmdSpec
+        , Just $ CmdSpec
           { csAlias = "date"
           , csDepends = Nothing
           , csRunnable = Run $ Date "%Y-%m-%d %H:%M:%S " "date" 10
           }
         ]
+  return $ BarRegions
+    { brLeft = left
+    , brCenter = []
+    , brRight = catMaybes right
     }
 
 fmtSpecs :: [CmdSpec] -> String
@@ -264,6 +288,6 @@ config br confDir = defaultConfig
 
 main :: IO ()
 main = do
-  br <- mapRegionsM filterSpecs myCommands
+  br <- mapRegionsM filterSpecs =<< myCommands
   dir <- getXMonadDir
   xmobar $ config br dir

my-xmonad.cabal

@@ -65,6 +65,8 @@ executable xmobar
                  , my-xmonad
                  , xmobar
                  , xmonad >= 0.13
+                 , filepath >= 1.4.2.1
                  , xmonad-contrib >= 0.13
+                 , directory >= 1.3.3.0
     default-language: Haskell2010
     ghc-options: -Wall -Werror -fno-warn-missing-signatures -threaded