Stable version 0.3.1

This release is dedicated to the Flycheck team,
even though ShellCheck is written entirely in Vim.

README

@@ -27,6 +27,12 @@ On Ubuntu and similar, use:
 For older releases, you may have to use:
   apt-get install ghc6 libghc6-parsec3-dev libghc6-quickcheck2-dev libghc6-json-dev libghc-regex-compat-dev cabal-install
 
+On Mac OS X with homebrew (http://brew.sh/), use:
+  brew install cabal-install
+
+On Mac OS X with MacPorts (http://www.macports.org/), use:
+  port install hs-cabal-install
+
 Executables can be built with cabal. Tests currently still rely on a Makefile.
 
 Install:

ShellCheck.cabal

@@ -1,5 +1,6 @@
 Name:             ShellCheck
-Version:          0.3.0
+-- Must also be updated in ShellCheck/Data.hs :
+Version:          0.3.1
 Synopsis:         Shell script analysis tool
 License:          OtherLicense
 License-file:     LICENSE

ShellCheck/AST.hs

@@ -26,6 +26,8 @@ data Id = Id Int deriving (Show, Eq, Ord)
 data Quoted = Quoted | Unquoted deriving (Show, Eq)
 data Dashed = Dashed | Undashed deriving (Show, Eq)
 data AssignmentMode = Assign | Append deriving (Show, Eq)
+data FunctionKeyword = FunctionKeyword Bool deriving (Show, Eq)
+data FunctionParentheses = FunctionParentheses Bool deriving (Show, Eq)
 
 data Token =
     TA_Base Id String Token
@@ -80,7 +82,7 @@ data Token =
     | T_For Id
     | T_ForArithmetic Id Token Token Token [Token]
     | T_ForIn Id String [Token] [Token]
-    | T_Function Id String Token
+    | T_Function Id FunctionKeyword FunctionParentheses String Token
     | T_GREATAND Id
     | T_Glob Id String
     | T_Greater Id
@@ -218,7 +220,7 @@ analyze f g i t =
         return $ T_ForArithmetic id x y z list
 
     delve (T_Script id s l) = dl l $ T_Script id s
-    delve (T_Function id name body) = d1 body $ T_Function id name
+    delve (T_Function id a b name body) = d1 body $ T_Function id a b name
     delve (T_Condition id typ token) = d1 token $ T_Condition id typ
     delve (T_Extglob id str l) = dl l $ T_Extglob id str
     delve (T_DollarBraced id op) = d1 op $ T_DollarBraced id
@@ -308,7 +310,7 @@ getId t = case t of
         T_ForIn id _ _ _  -> id
         T_SelectIn id _ _ _  -> id
         T_CaseExpression id _ _ -> id
-        T_Function id _ _  -> id
+        T_Function id _ _ _ _  -> id
         T_Arithmetic id _  -> id
         T_Script id _ _  -> id
         T_Condition id _ _  -> id
@@ -342,3 +344,10 @@ doAnalysis f t = analyze f blank id t
 doStackAnalysis startToken endToken t = analyze startToken endToken id t
 doTransform i t = runIdentity $ analyze blank blank i t
 
+isLoop t = case t of
+        T_WhileExpression _ _ _  -> True
+        T_UntilExpression _ _ _  -> True
+        T_ForIn _ _ _ _  -> True
+        T_ForArithmetic _ _ _ _ _ -> True
+        T_SelectIn _ _ _ _  -> True
+        _ -> False

ShellCheck/Data.hs

@@ -1,8 +1,10 @@
 module ShellCheck.Data where
 
+shellcheckVersion = "0.3.1"  -- Must also be updated in ShellCheck.cabal
+
 internalVariables = [
     -- Generic
-    "", "_",
+    "", "_", "rest", "REST",
 
     -- Bash
     "BASH", "BASHOPTS", "BASHPID", "BASH_ALIASES", "BASH_ARGC",
@@ -41,13 +43,13 @@ internalVariables = [
   ]
 
 variablesWithoutSpaces = [
-    "$", "-", "?", "!", 
+    "$", "-", "?", "!",
     "BASHPID", "BASH_ARGC", "BASH_LINENO", "BASH_SUBSHELL", "EUID", "LINENO",
     "OPTIND", "PPID", "RANDOM", "SECONDS", "SHELLOPTS", "SHLVL", "UID",
     "COLUMNS", "HISTFILESIZE", "HISTSIZE", "LINES"
   ]
 
-commonCommands = [ 
+commonCommands = [
     "admin", "alias", "ar", "asa", "at", "awk", "basename", "batch",
     "bc", "bg", "break", "c99", "cal", "cat", "cd", "cflow", "chgrp",
     "chmod", "chown", "cksum", "cmp", "colon", "comm", "command",
@@ -70,5 +72,5 @@ commonCommands = [
     "unalias", "uname", "uncompress", "unexpand", "unget", "uniq",
     "unlink", "unset", "uucp", "uudecode", "uuencode", "uustat", "uux",
     "val", "vi", "wait", "wc", "what", "who", "write", "xargs", "yacc",
-    "zcat" 
+    "zcat"
   ]

ShellCheck/Parser.hs

@@ -17,7 +17,7 @@
 -}
 {-# LANGUAGE NoMonomorphismRestriction #-}
 
-module ShellCheck.Parser (Note(..), Severity(..), parseShell, ParseResult(..), ParseNote(..), notesFromMap, Metadata(..), sortNotes) where
+module ShellCheck.Parser (Note(..), Severity(..), parseShell, ParseResult(..), ParseNote(..), sortNotes, noteToParseNote) where
 
 import ShellCheck.AST
 import ShellCheck.Data
@@ -34,8 +34,6 @@ import System.IO
 import Text.Parsec.Error
 import GHC.Exts (sortWith)
 
-lastError = 1074
-
 backslash = char '\\'
 linefeed = (optional carriageReturn) >> char '\n'
 singleQuote = char '\'' <|> unicodeSingleQuote
@@ -100,20 +98,20 @@ nbsp = do
     return ' '
 
 --------- Message/position annotation on top of user state
-data Note = Note Severity Code String deriving (Show, Eq)
+data Note = Note Id Severity Code String deriving (Show, Eq)
 data ParseNote = ParseNote SourcePos Severity Code String deriving (Show, Eq)
-data Metadata = Metadata SourcePos [Note] deriving (Show)
 data Severity = ErrorC | WarningC | InfoC | StyleC deriving (Show, Eq, Ord)
 data Context = ContextName SourcePos String | ContextAnnotation [Annotation]
 type Code = Integer
 
-codeForNote (Note _ code _) = code
 codeForParseNote (ParseNote _ _ code _) = code
+noteToParseNote map (Note id severity code message) =
+        ParseNote pos severity code message
+    where
+        pos = fromJust $ Map.lookup id map
 
 initialState = (Id $ -1, Map.empty, [])
 
-getInitialMeta pos = Metadata pos []
-
 getLastId = do
     (id, _, _) <- getState
     return id
@@ -121,7 +119,7 @@ getLastId = do
 getNextIdAt sourcepos = do
     (id, map, notes) <- getState
     let newId = incId id
-    let newMap = Map.insert newId (getInitialMeta sourcepos) map
+    let newMap = Map.insert newId sourcepos map
     putState (newId, newMap, notes)
     return newId
   where incId (Id n) = (Id $ n+1)
@@ -189,11 +187,6 @@ parseProblemAt pos level code msg = do
         Ms.modify (\(list, current) -> ((ParseNote pos level code msg):list, current))
 
 -- Store non-parse problems inside
-addNoteFor id note = modifyMap $ Map.adjust (\(Metadata pos notes) -> Metadata pos (note:notes)) id
-
-addNote note = do
-    id <- getLastId
-    addNoteFor id note
 
 parseNote c l a = do
     pos <- getPosition
@@ -269,6 +262,7 @@ readConditionContents single = do
   where
     typ = if single then SingleBracket else DoubleBracket
     readCondBinaryOp = try $ do
+        optional guardArithmetic
         id <- getNextId
         op <- (choice $ (map tryOp ["==", "!=", "<=", ">=", "=~", ">", "<", "=", "\\<=", "\\>=", "\\<", "\\>"])) <|> otherOp
         hardCondSpacing
@@ -284,6 +278,13 @@ readConditionContents single = do
             when (s == "-a" || s == "-o") $ fail "Wrong operator"
             return $ TC_Binary id typ s
 
+    guardArithmetic = do
+        try . lookAhead $ disregard (oneOf "+*/%") <|> disregard (string "- ")
+        parseProblem ErrorC 1076 $
+            if single
+            then "Trying to do math? Use e.g. [ $((i/2+7)) -ge 18 ]."
+            else "Trying to do math? Use e.g. [[ $((i/2+7)) -ge 18 ]]."
+
     readCondUnaryExp = do
       op <- readCondUnaryOp
       pos <- getPosition
@@ -325,16 +326,13 @@ readConditionContents single = do
     readCondAndOp = do
         id <- getNextId
         x <- try (string "&&" <|> string "-a")
-        when (single && x == "&&") $ addNoteFor id $ Note ErrorC 1022 "You can't use && inside [..]. Use [[..]] instead."
-        when (not single && x == "-a") $ addNoteFor id $ Note ErrorC 1023 "In [[..]], use && instead of -a."
         softCondSpacing
         return $ TC_And id typ x
 
     readCondOrOp = do
+        optional guardArithmetic
         id <- getNextId
         x <- try (string "||" <|> string "-o")
-        when (single && x == "||") $ addNoteFor id $ Note ErrorC 1024 "You can't use || inside [..]. Use [[..]] instead."
-        when (not single && x == "-o") $ addNoteFor id $ Note ErrorC 1025 "In [[..]], use || instead of -o."
         softCondSpacing
         return $ TC_Or id typ x
 
@@ -444,6 +442,8 @@ prop_aA = isOk readArithmeticContents "! $?"
 prop_aB = isOk readArithmeticContents "10#08 * 16#f"
 prop_aC = isOk readArithmeticContents "\"$((3+2))\" + '37'"
 prop_aD = isOk readArithmeticContents "foo[9*y+x]++"
+prop_aE = isOk readArithmeticContents "1+`echo 2`"
+prop_aF = isOk readArithmeticContents "foo[`echo foo | sed s/foo/4/g` * 3] + 4"
 readArithmeticContents =
     readSequence
   where
@@ -477,7 +477,7 @@ readArithmeticContents =
 
     readExpansion = do
         id <- getNextId
-        x <- readNormalDollar
+        x <- readNormalDollar <|> readBackTicked
         spacing
         return $ TA_Expansion id x
 
@@ -1348,6 +1348,8 @@ readCmdWord = do
 prop_readIfClause = isOk readIfClause "if false; then foo; elif true; then stuff; more stuff; else cows; fi"
 prop_readIfClause2 = isWarning readIfClause "if false; then; echo oo; fi"
 prop_readIfClause3 = isWarning readIfClause "if false; then true; else; echo lol; fi"
+prop_readIfClause4 = isWarning readIfClause "if false; then true; else if true; then echo lol; fi"
+prop_readIfClause5 = isOk readIfClause "if false; then true; else\nif true; then echo lol; fi; fi"
 readIfClause = called "if expression" $ do
     id <- getNextId
     pos <- getPosition
@@ -1389,7 +1391,9 @@ readIfPart = do
 
 readElifPart = called "elif clause" $ do
     pos <- getPosition
-    g_Elif
+    correctElif <- elif
+    when (not correctElif) $
+        parseProblemAt pos ErrorC 1075 "Use 'elif' instead of 'else if'."
     allspacing
     condition <- readTerm
     g_Then
@@ -1398,8 +1402,12 @@ readElifPart = called "elif clause" $ do
     verifyNotEmptyIf "then"
     action <- readTerm
     return (condition, action)
+  where
+    elif = (g_Elif >> return True) <|>
+        (try $ g_Else >> g_If >> return False)
 
 readElsePart = called "else clause" $ do
+    pos <- getPosition
     g_Else
     acceptButWarn g_Semi ErrorC 1053 "No semicolons directly after 'else'."
     allspacing
@@ -1478,15 +1486,14 @@ prop_readForClause6 = isOk readForClause "for ((;;))\ndo echo $i\ndone"
 prop_readForClause7 = isOk readForClause "for ((;;)) do echo $i\ndone"
 prop_readForClause8 = isOk readForClause "for ((;;)) ; do echo $i\ndone"
 prop_readForClause9 = isOk readForClause "for i do true; done"
+prop_readForClause10= isOk readForClause "for ((;;)) { true; }"
 readForClause = called "for loop" $ do
     pos <- getPosition
     (T_For id) <- g_For
     spacing
-    typ <- (readRegular <|> readArithmetic)
-    group <- readDoGroup pos
-    typ id group
+    readRegular id pos <|> readArithmetic id pos
   where
-    readArithmetic = called "arithmetic for condition" $ do
+    readArithmetic id pos = called "arithmetic for condition" $ do
         try $ string "(("
         x <- readArithmeticContents
         char ';' >> spacing
@@ -1497,13 +1504,19 @@ readForClause = called "for loop" $ do
         string "))"
         spacing
         optional $ readSequentialSep >> spacing
-        return $ \id group -> (return $ T_ForArithmetic id x y z group)
+        group <- readBraced <|> readDoGroup pos
+        return $ T_ForArithmetic id x y z group
 
-    readRegular = do
+    readBraced = do
+        (T_BraceGroup _ list) <- readBraceGroup
+        return list
+
+    readRegular id pos = do
         name <- readVariableName
         spacing
         values <- readInClause <|> (optional readSequentialSep >> return [])
-        return $ \id group -> (return $ T_ForIn id name values group)
+        group <- readDoGroup pos
+        return $ T_ForIn id name values group
 
 prop_readSelectClause1 = isOk readSelectClause "select foo in *; do echo $foo; done"
 prop_readSelectClause2 = isOk readSelectClause "select foo; do echo $foo; done"
@@ -1569,61 +1582,52 @@ readCaseItem = called "case item" $ do
 
 prop_readFunctionDefinition = isOk readFunctionDefinition "foo() { command foo --lol \"$@\"; }"
 prop_readFunctionDefinition1 = isOk readFunctionDefinition "foo   (){ command foo --lol \"$@\"; }"
-prop_readFunctionDefinition2 = isWarning readFunctionDefinition "function foo() { command foo --lol \"$@\"; }"
-prop_readFunctionDefinition3 = isWarning readFunctionDefinition "function foo { lol; }"
 prop_readFunctionDefinition4 = isWarning readFunctionDefinition "foo(a, b) { true; }"
 prop_readFunctionDefinition5 = isOk readFunctionDefinition ":(){ :|:;}"
 prop_readFunctionDefinition6 = isOk readFunctionDefinition "?(){ foo; }"
 prop_readFunctionDefinition7 = isOk readFunctionDefinition "..(){ cd ..; }"
 prop_readFunctionDefinition8 = isOk readFunctionDefinition "foo() (ls)"
 readFunctionDefinition = called "function" $ do
-    id <- getNextId
-    name <- try readFunctionSignature
+    functionSignature <- try readFunctionSignature
     allspacing
     (disregard (lookAhead $ oneOf "{(") <|> parseProblem ErrorC 1064 "Expected a { to open the function definition.")
     group <- readBraceGroup <|> readSubshell
-    return $ T_Function id name group
-
-
-readFunctionSignature = do
-    readWithFunction <|> readWithoutFunction
+    return $ functionSignature group
   where
-    readWithFunction = do
-        pos <- getPosition
-        try $ do
-            string "function"
-            whitespace
-        parseProblemAt pos InfoC 1005 "Drop the keyword 'function'. It's optional in Bash but invalid in other shells."
-        spacing
-        name <- readFunctionName
-        optional spacing
-        pos <- getPosition
-        readParens <|> do
-            parseProblemAt pos InfoC 1006 "Include '()' after the function name (in addition to dropping 'function')."
-        return name
+    readFunctionSignature = do
+        readWithFunction <|> readWithoutFunction
+      where
+        readWithFunction = do
+            id <- getNextId
+            try $ do
+                string "function"
+                whitespace
+            spacing
+            name <- readFunctionName
+            optional spacing
+            hasParens <- wasIncluded readParens
+            return $ T_Function id (FunctionKeyword True) (FunctionParentheses hasParens) name
 
-    readWithoutFunction = try $ do
-        name <- readFunctionName
-        optional spacing
-        readParens
-        return name
-
-    readParens = do
-        g_Lparen
-        optional spacing
-        g_Rparen <|> do
-            parseProblem ErrorC 1065 "Trying to declare parameters? Don't. Use () and refer to params as $1, $2.."
-            many $ noneOf "\n){"
-            g_Rparen
-        return ()
-
-    readFunctionName = many1 functionChars
+        readWithoutFunction = try $ do
+            id <- getNextId
+            name <- readFunctionName
+            optional spacing
+            readParens
+            return $ T_Function id (FunctionKeyword False) (FunctionParentheses True) name
 
+        readParens = do
+            g_Lparen
+            optional spacing
+            g_Rparen <|> do
+                parseProblem ErrorC 1065 "Trying to declare parameters? Don't. Use () and refer to params as $1, $2.."
+                many $ noneOf "\n){"
+                g_Rparen
+            return ()
 
+        readFunctionName = many1 functionChars
 
 readPattern = (readNormalWord `thenSkip` spacing) `sepBy1` (char '|' `thenSkip` spacing)
 
-
 prop_readCompoundCommand = isOk readCompoundCommand "{ echo foo; }>/dev/null"
 readCompoundCommand = do
     id <- getNextId
@@ -1865,7 +1869,7 @@ isOk p s = (fst cs) && (null . snd $ cs) where cs = checkString p s
 
 checkString parser string =
     case rp (parser >> eof >> getState) "-" string of
-        (Right (tree, map, notes), (problems, _)) -> (True, (notesFromMap map) ++ notes ++ problems)
+        (Right (tree, map, notes), (problems, _)) -> (True, notes ++ problems)
         (Left _, (n, _)) -> (False, n)
 
 parseWithNotes parser = do
@@ -1874,16 +1878,11 @@ parseWithNotes parser = do
     parseNotes <- getParseNotes
     return (item, map, nub . sortNotes $ parseNotes)
 
-toParseNotes (Metadata pos list) = map (\(Note level code note) -> ParseNote pos level code note) list
-notesFromMap map = Map.fold (\x -> (++) (toParseNotes x)) [] map
-
-getAllNotes result = (concatMap (notesFromMap . snd) (maybeToList . parseResult $ result)) ++ (parseNotes result)
-
 compareNotes (ParseNote pos1 level1 _ s1) (ParseNote pos2 level2 _ s2) = compare (pos1, level1) (pos2, level2)
 sortNotes = sortBy compareNotes
 
 
-data ParseResult = ParseResult { parseResult :: Maybe (Token, Map.Map Id Metadata), parseNotes :: [ParseNote] } deriving (Show)
+data ParseResult = ParseResult { parseResult :: Maybe (Token, Map.Map Id SourcePos), parseNotes :: [ParseNote] } deriving (Show)
 
 makeErrorFor parsecError =
     ParseNote (errorPos parsecError) ErrorC 1072 $ getStringFromParsec $ errorMessages parsecError
@@ -1903,9 +1902,11 @@ getStringFromParsec errors =
 
 parseShell filename contents = do
     case rp (parseWithNotes readScript) filename contents of
-        (Right (script, map, notes), (parsenotes, _)) -> ParseResult (Just (script, map)) (nub $ sortNotes $ notes ++ parsenotes)
-        (Left err, (p, context)) -> ParseResult Nothing (nub $ sortNotes $ p ++ (notesForContext context) ++ ([makeErrorFor err]))
-
+        (Right (script, map, notes), (parsenotes, _)) ->
+            ParseResult (Just (script, map)) (nub $ sortNotes $ notes ++ parsenotes)
+        (Left err, (p, context)) ->
+            ParseResult Nothing
+                (nub $ sortNotes $ p ++ (notesForContext context) ++ ([makeErrorFor err]))
   where
     isName (ContextName _ _) = True
     isName _ = False

ShellCheck/Simple.hs

@@ -25,28 +25,28 @@ import Data.List
 
 
 prop_findsParseIssue =
-    let comments = shellCheck "echo \"$12\"" in
+    let comments = shellCheck "echo \"$12\"" [] in
         (length comments) == 1 && (scCode $ head comments) == 1037
 prop_commentDisablesParseIssue1 =
-    null $ shellCheck "#shellcheck disable=SC1037\necho \"$12\""
+    null $ shellCheck "#shellcheck disable=SC1037\necho \"$12\"" []
 prop_commentDisablesParseIssue2 =
-    null $ shellCheck "#shellcheck disable=SC1037\n#lol\necho \"$12\""
+    null $ shellCheck "#shellcheck disable=SC1037\n#lol\necho \"$12\"" []
 
 prop_findsAnalysisIssue =
-    let comments = shellCheck "echo $1" in
+    let comments = shellCheck "echo $1" [] in
         (length comments) == 1 && (scCode $ head comments) == 2086
 prop_commentDisablesAnalysisIssue1 =
-    null $ shellCheck "#shellcheck disable=SC2086\necho $1"
+    null $ shellCheck "#shellcheck disable=SC2086\necho $1" []
 prop_commentDisablesAnalysisIssue2 =
-    null $ shellCheck "#shellcheck disable=SC2086\n#lol\necho $1"
+    null $ shellCheck "#shellcheck disable=SC2086\n#lol\necho $1" []
 
-shellCheck :: String -> [ShellCheckComment]
-shellCheck script =
+shellCheck :: String -> [AnalysisOption] -> [ShellCheckComment]
+shellCheck script options =
     let (ParseResult result notes) = parseShell "-" script in
         let allNotes = notes ++ (concat $ maybeToList $ do
-            (tree, map) <- result
-            let newMap = runAllAnalytics tree map
-            return $ notesFromMap $ filterByAnnotation tree newMap
+            (tree, posMap) <- result
+            let list = runAnalytics options tree
+            return $ map (noteToParseNote posMap) $ filterByAnnotation tree list
             )
         in
             map formatNote $ nub $ sortNotes allNotes

shellcheck.1.md

@@ -30,8 +30,11 @@ corner cases can cause delayed failures.
     options are cumulative, but all the codes can be specified at once,
     comma-separated as a single argument.
 
-Also note that shellcheck supports multiple Bourne shell dialects, and
-examines the file's shebang to determine which one to use.
+**-s**\ *shell*,\ **--shell=***shell*
+
+:   Specify Bourne shell dialect. Valid values are *sh*, *bash*, *ksh* and
+    *zsh*. The default is to use the file's shebang, or *bash* if the target
+    shell can't be determined.
 
 # FORMATS
 

shellcheck.hs

@@ -18,10 +18,13 @@
 import Control.Exception
 import Control.Monad
 import Data.Char
+import Data.Maybe
 import GHC.Exts
 import GHC.IO.Device
 import Prelude hiding (catch)
+import ShellCheck.Data
 import ShellCheck.Simple
+import ShellCheck.Analytics
 import System.Console.GetOpt
 import System.Directory
 import System.Environment
@@ -37,7 +40,11 @@ options = [
     Option ['f'] ["format"]
         (ReqArg (Flag "format") "FORMAT") "output format",
     Option ['e'] ["exclude"]
-        (ReqArg (Flag "exclude") "CODE1,CODE2..") "exclude types of warnings"
+        (ReqArg (Flag "exclude") "CODE1,CODE2..") "exclude types of warnings",
+    Option ['s'] ["shell"]
+        (ReqArg (Flag "shell") "SHELLNAME") "Specify dialect (bash,sh,ksh,zsh)",
+    Option ['V'] ["version"]
+        (NoArg $ Flag "version" "true") "Print version information"
     ]
 
 printErr = hPutStrLn stderr
@@ -57,14 +64,9 @@ instance JSON ShellCheckComment where
 
 parseArguments argv =
     case getOpt Permute options argv of
-        (opts, files, []) ->
-            if not $ null files
-              then
-                return $ Just (opts, files)
-              else do
-                printErr "No files specified.\n"
-                printErr $ usageInfo header options
-                exitWith syntaxFailure
+        (opts, files, []) -> do
+            verifyOptions opts files
+            return $ Just (opts, files)
 
         (_, _, errors) -> do
             printErr $ (concat errors) ++ "\n" ++ usageInfo header options
@@ -200,7 +202,14 @@ commentsFor options file =
     liftM (getComments options) $ readContents file
 
 getComments options contents =
-    excludeCodes (getExclusions options) $ shellCheck contents
+    excludeCodes (getExclusions options) $ shellCheck contents analysisOptions
+  where
+    analysisOptions = catMaybes [ shellOption ]
+    shellOption = do
+        option <- getOption options "shell"
+        sh <- shellForExecutable option
+        return $ ForceShell sh
+
 
 readContents file = if file == "-" then getContents else readFile file
 
@@ -216,9 +225,9 @@ makeNonVirtual comments contents =
         real rest (r+1) (v + 8 - (v `mod` 8)) target
     real (_:rest) r v target = real rest (r+1) (v+1) target
 
-getOption [] _ def = def
-getOption ((Flag var val):_) name _ | name == var = val
-getOption (_:rest) flag def = getOption rest flag def
+getOption [] _ = Nothing
+getOption ((Flag var val):_) name | name == var = return val
+getOption (_:rest) flag = getOption rest flag
 
 getOptions options name =
     map (\(Flag _ val) -> val) . filter (\(Flag var _) -> var == name) $ options
@@ -256,8 +265,8 @@ main = do
     exitWith code
 
 process Nothing = return False
-process (Just (options, files)) =
-  let format = getOption options "format" "tty" in
+process (Just (options, files)) = do
+  let format = fromMaybe "tty" $ getOption options "format" in
     case Map.lookup format formats of
         Nothing -> do
             printErr $ "Unknown format " ++ format
@@ -268,3 +277,24 @@ process (Just (options, files)) =
         Just f -> do
             f options files
 
+verifyOptions opts files = do
+    when (isJust $ getOption opts "version") printVersionAndExit
+
+    let shell = getOption opts "shell" in
+        if isNothing shell
+        then return ()
+        else when (isNothing $ shell >>= shellForExecutable) $ do
+                printErr $ "Unknown shell: " ++ (fromJust shell)
+                exitWith supportFailure
+
+    when (null files) $ do
+        printErr "No files specified.\n"
+        printErr $ usageInfo header options
+        exitWith syntaxFailure
+
+printVersionAndExit = do
+    putStrLn $ "ShellCheck - shell script analysis tool"
+    putStrLn $ "version: " ++ shellcheckVersion
+    putStrLn $ "license: GNU Affero General Public License, version 3"
+    putStrLn $ "website: http://www.shellcheck.net"
+    exitWith ExitSuccess