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-rw-r--r--src/Xmobar/Environment.hs49
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diff --git a/src/Xmobar/Environment.hs b/src/Xmobar/Environment.hs
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+-----------------------------------------------------------------------------
+-- |
+-- Module : XMobar.Environment
+-- Copyright : (c) William Song
+-- License : BSD-style (see LICENSE)
+--
+-- Maintainer : Will Song <incertia@incertia.net>
+-- Stability : stable
+-- Portability : portable
+--
+-- A function to expand environment variables in strings
+--
+-----------------------------------------------------------------------------
+module Xmobar.Environment(expandEnv) where
+
+import Control.Applicative ((<$>))
+import Data.Maybe (fromMaybe)
+import System.Environment (lookupEnv)
+
+expandEnv :: String -> IO String
+expandEnv "" = return ""
+expandEnv (c:s) = case c of
+ '$' -> do
+ envVar <- fromMaybe "" <$> lookupEnv e
+ remainder <- expandEnv s'
+ return $ envVar ++ remainder
+ where (e, s') = getVar s
+ getVar "" = ("", "")
+ getVar ('{':s'') = (takeUntil "}" s'', drop 1 . dropUntil "}" $ s'')
+ getVar s'' = (takeUntil filterstr s'', dropUntil filterstr s'')
+ filterstr = ",./? \t;:\"'~`!@#$%^&*()<>-+=\\|"
+ takeUntil f = takeWhile (not . flip elem f)
+ dropUntil f = dropWhile (not . flip elem f)
+
+ '\\' -> case s == "" of
+ True -> return "\\"
+ False -> do
+ remainder <- expandEnv $ drop 1 s
+ return $ escString s ++ remainder
+ where escString s' = let (cc:_) = s' in
+ case cc of
+ 't' -> "\t"
+ 'n' -> "\n"
+ '$' -> "$"
+ _ -> [cc]
+
+ _ -> do
+ remainder <- expandEnv s
+ return $ c : remainder