Adds support for a SHELLCHECK_OPTS environment variable.

ShellCheck/Regex.hs

@@ -71,3 +71,10 @@ subRegex re input replacement = f input
         (before, match, after) <- matchM re str :: Maybe (String, String, String)
         when (null match) $ error ("Internal error: substituted empty in " ++ str)
         return $ before ++ replacement ++ f after
+
+-- Split a string based on a regex.
+splitOn :: String -> Regex -> [String]
+splitOn input re =
+    case matchM re input :: Maybe (String, String, String) of
+        Just (before, match, after) -> before : after `splitOn` re
+        Nothing -> [input]

shellcheck.1.md

@@ -151,6 +151,13 @@ Valid keys are:
     used to tell shellcheck where to look for a file whose name is determined
     at runtime, or to skip a source by telling it to use `/dev/null`.
 
+# ENVIRONMENT VARIABLES
+The environment variable `SHELLCHECK_OPTS` can be set with default flags:
+
+    export SHELLCHECK_OPTS='--shell=bash --exclude=SC2016'
+
+Its value will be split on spaces and prepended to the command line on each
+invocation.
 
 # AUTHOR
 ShellCheck is written and maintained by Vidar Holen.

shellcheck.hs

@@ -20,6 +20,7 @@
 import ShellCheck.Data
 import ShellCheck.Checker
 import ShellCheck.Interface
+import ShellCheck.Regex
 
 import ShellCheck.Formatter.Format
 import qualified ShellCheck.Formatter.CheckStyle
@@ -123,8 +124,17 @@ getExclusions options =
 
 toStatus = liftM (either id id) . runExceptT
 
+getEnvArgs = do
+    opts <- getEnv "SHELLCHECK_OPTS" `catch` cantWaitForLookupEnv
+    return . filter (not . null) $ opts `splitOn` mkRegex " +"
+  where
+    cantWaitForLookupEnv :: IOException -> IO String
+    cantWaitForLookupEnv = const $ return ""
+
 main = do
-    args <- getArgs
+    params <- getArgs
+    envOpts  <- getEnvArgs
+    let args = envOpts ++ params
     status <- toStatus $ do
         (flags, files) <- parseArguments args
         process flags files