From be8e4b2b8aac4177ef31092397f1ea2cad8e66ad Mon Sep 17 00:00:00 2001
From: Grische <github@grische.xyz>
Date: Sat, 25 Nov 2023 12:44:46 +0100
Subject: [PATCH 1/9] add basic busybox sh support

---
 CHANGELOG.md                  | 1 +
 src/ShellCheck/ASTLib.hs      | 7 ++++---
 src/ShellCheck/Analytics.hs   | 4 ++--
 src/ShellCheck/AnalyzerLib.hs | 4 ++--
 src/ShellCheck/Data.hs        | 2 ++
 src/ShellCheck/Interface.hs   | 5 ++---
 src/ShellCheck/Parser.hs      | 5 +++--
 7 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b9ce1fb20..897aa2742 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@
 - SC3015: Warn bashism `test _ =~ _` like in [ ]
 - SC3016: Warn bashism `test -v _` like in [ ]
 - SC3017: Warn bashism `test -a _` like in [ ]
+- Added support for busybox sh
 
 ### Fixed
 - source statements with here docs now work correctly
diff --git a/src/ShellCheck/ASTLib.hs b/src/ShellCheck/ASTLib.hs
index 64fa7625f..cf55498e2 100644
--- a/src/ShellCheck/ASTLib.hs
+++ b/src/ShellCheck/ASTLib.hs
@@ -758,8 +758,8 @@ prop_executableFromShebang6 = executableFromShebang "/usr/bin/env --split-string
 prop_executableFromShebang7 = executableFromShebang "/usr/bin/env --split-string bash -x" == "bash"
 prop_executableFromShebang8 = executableFromShebang "/usr/bin/env --split-string foo=bar bash -x" == "bash"
 prop_executableFromShebang9 = executableFromShebang "/usr/bin/env foo=bar dash" == "dash"
-prop_executableFromShebang10 = executableFromShebang "/bin/busybox sh" == "ash"
-prop_executableFromShebang11 = executableFromShebang "/bin/busybox ash" == "ash"
+prop_executableFromShebang10 = executableFromShebang "/bin/busybox sh" == "busybox sh"
+prop_executableFromShebang11 = executableFromShebang "/bin/busybox ash" == "busybox ash"
 
 -- Get the shell executable from a string like '/usr/bin/env bash'
 executableFromShebang :: String -> String
@@ -776,7 +776,8 @@ executableFromShebang = shellFor
             [x] -> basename x
             (first:second:args) | basename first == "busybox" ->
                 case basename second of
-                   "sh" -> "ash" -- busybox sh is ash
+                   "sh" -> "busybox sh"
+                   "ash" -> "busybox ash"
                    x -> x
             (first:args) | basename first == "env" ->
                 fromEnvArgs args
diff --git a/src/ShellCheck/Analytics.hs b/src/ShellCheck/Analytics.hs
index dadf51299..5df2f354e 100644
--- a/src/ShellCheck/Analytics.hs
+++ b/src/ShellCheck/Analytics.hs
@@ -646,10 +646,10 @@ prop_checkShebang9 = verifyNotTree checkShebang "# shellcheck shell=sh\ntrue"
 prop_checkShebang10 = verifyNotTree checkShebang "#!foo\n# shellcheck shell=sh ignore=SC2239\ntrue"
 prop_checkShebang11 = verifyTree checkShebang "#!/bin/sh/\ntrue"
 prop_checkShebang12 = verifyTree checkShebang "#!/bin/sh/ -xe\ntrue"
-prop_checkShebang13 = verifyTree checkShebang "#!/bin/busybox sh"
+prop_checkShebang13 = verifyNotTree checkShebang "#!/bin/busybox sh"
 prop_checkShebang14 = verifyNotTree checkShebang "#!/bin/busybox sh\n# shellcheck shell=sh\n"
 prop_checkShebang15 = verifyNotTree checkShebang "#!/bin/busybox sh\n# shellcheck shell=dash\n"
-prop_checkShebang16 = verifyTree checkShebang "#!/bin/busybox ash"
+prop_checkShebang16 = verifyNotTree checkShebang "#!/bin/busybox ash"
 prop_checkShebang17 = verifyNotTree checkShebang "#!/bin/busybox ash\n# shellcheck shell=dash\n"
 prop_checkShebang18 = verifyNotTree checkShebang "#!/bin/busybox ash\n# shellcheck shell=sh\n"
 checkShebang params (T_Annotation _ list t) =
diff --git a/src/ShellCheck/AnalyzerLib.hs b/src/ShellCheck/AnalyzerLib.hs
index ca928fd7a..d864e32af 100644
--- a/src/ShellCheck/AnalyzerLib.hs
+++ b/src/ShellCheck/AnalyzerLib.hs
@@ -284,8 +284,8 @@ prop_determineShell7 = determineShellTest "#! /bin/ash" == Dash
 prop_determineShell8 = determineShellTest' (Just Ksh) "#!/bin/sh" == Sh
 prop_determineShell9 = determineShellTest "#!/bin/env -S dash -x" == Dash
 prop_determineShell10 = determineShellTest "#!/bin/env --split-string= dash -x" == Dash
-prop_determineShell11 = determineShellTest "#!/bin/busybox sh" == Dash -- busybox sh is a specific shell, not posix sh
-prop_determineShell12 = determineShellTest "#!/bin/busybox ash" == Dash
+prop_determineShell11 = determineShellTest "#!/bin/busybox sh" == BusyboxSh -- busybox sh is a specific shell, not posix sh
+prop_determineShell12 = determineShellTest "#!/bin/busybox ash" == BusyboxSh
 
 determineShellTest = determineShellTest' Nothing
 determineShellTest' fallbackShell = determineShell fallbackShell . fromJust . prRoot . pScript
diff --git a/src/ShellCheck/Data.hs b/src/ShellCheck/Data.hs
index 550ff87a3..6a8712316 100644
--- a/src/ShellCheck/Data.hs
+++ b/src/ShellCheck/Data.hs
@@ -156,6 +156,8 @@ shellForExecutable name =
         "sh"    -> return Sh
         "bash"  -> return Bash
         "bats"  -> return Bash
+        "busybox sh"  -> return BusyboxSh
+        "busybox ash"  -> return BusyboxSh
         "dash"  -> return Dash
         "ash"   -> return Dash -- There's also a warning for this.
         "ksh"   -> return Ksh
diff --git a/src/ShellCheck/Interface.hs b/src/ShellCheck/Interface.hs
index 077212f13..c574cee14 100644
--- a/src/ShellCheck/Interface.hs
+++ b/src/ShellCheck/Interface.hs
@@ -28,7 +28,7 @@ module ShellCheck.Interface
     , AnalysisSpec(asScript, asShellType, asFallbackShell, asExecutionMode, asCheckSourced, asTokenPositions, asOptionalChecks)
     , AnalysisResult(arComments)
     , FormatterOptions(foColorOption, foWikiLinkCount)
-    , Shell(Ksh, Sh, Bash, Dash)
+    , Shell(Ksh, Sh, Bash, Dash, BusyboxSh)
     , ExecutionMode(Executed, Sourced)
     , ErrorMessage
     , Code
@@ -221,7 +221,7 @@ newCheckDescription = CheckDescription {
     }
 
 -- Supporting data types
-data Shell = Ksh | Sh | Bash | Dash deriving (Show, Eq)
+data Shell = Ksh | Sh | Bash | Dash | BusyboxSh deriving (Show, Eq)
 data ExecutionMode = Executed | Sourced deriving (Show, Eq)
 
 type ErrorMessage = String
@@ -335,4 +335,3 @@ mockedSystemInterface files = (newSystemInterface :: SystemInterface Identity) {
 mockRcFile rcfile mock = mock {
     siGetConfig = const . return $ Just (".shellcheckrc", rcfile)
 }
-
diff --git a/src/ShellCheck/Parser.hs b/src/ShellCheck/Parser.hs
index ffc58e211..abd4d9404 100644
--- a/src/ShellCheck/Parser.hs
+++ b/src/ShellCheck/Parser.hs
@@ -3349,8 +3349,8 @@ readScriptFile sourced = do
     verifyShebang pos s = do
         case isValidShell s of
             Just True -> return ()
-            Just False -> parseProblemAt pos ErrorC 1071 "ShellCheck only supports sh/bash/dash/ksh scripts. Sorry!"
-            Nothing -> parseProblemAt pos ErrorC 1008 "This shebang was unrecognized. ShellCheck only supports sh/bash/dash/ksh. Add a 'shell' directive to specify."
+            Just False -> parseProblemAt pos ErrorC 1071 "ShellCheck only supports sh/bash/dash/ksh/'busybox sh' scripts. Sorry!"
+            Nothing -> parseProblemAt pos ErrorC 1008 "This shebang was unrecognized. ShellCheck only supports sh/bash/dash/ksh/'busybox sh'. Add a 'shell' directive to specify."
 
     isValidShell s =
         let good = null s || any (`isPrefixOf` s) goodShells
@@ -3366,6 +3366,7 @@ readScriptFile sourced = do
         "sh",
         "ash",
         "dash",
+        "busybox sh",
         "bash",
         "bats",
         "ksh"

From 1e1045e73e0c66a947390785e95d924203e837fc Mon Sep 17 00:00:00 2001
From: Grische <github@grische.xyz>
Date: Sat, 25 Nov 2023 12:52:32 +0100
Subject: [PATCH 2/9] make busybox sh Dash-like

---
 src/ShellCheck/Analytics.hs           |  6 +++++-
 src/ShellCheck/AnalyzerLib.hs         |  4 ++++
 src/ShellCheck/Checks/Commands.hs     |  4 ++--
 src/ShellCheck/Checks/ShellSupport.hs | 12 +++++++-----
 4 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/ShellCheck/Analytics.hs b/src/ShellCheck/Analytics.hs
index 5df2f354e..108682a6f 100644
--- a/src/ShellCheck/Analytics.hs
+++ b/src/ShellCheck/Analytics.hs
@@ -1204,6 +1204,7 @@ checkNumberComparisons params (TC_Binary id typ op lhs rhs) = do
             case shellType params of
                 Sh -> return ()  -- These are unsupported and will be caught by bashism checks.
                 Dash -> err id 2073 $ "Escape \\" ++ op ++ " to prevent it redirecting."
+                BusyboxSh -> err id 2073 $ "Escape \\" ++ op ++ " to prevent it redirecting."
                 _ -> err id 2073 $ "Escape \\" ++ op ++ " to prevent it redirecting (or switch to [[ .. ]])."
 
     when (op `elem` arithmeticBinaryTestOps) $ do
@@ -2782,6 +2783,7 @@ checkFunctionDeclarations params
             when (hasKeyword && hasParens) $
                 err id 2111 "ksh does not allow 'function' keyword and '()' at the same time."
         Dash -> forSh
+        BusyboxSh -> forSh
         Sh   -> forSh
 
     where
@@ -4044,7 +4046,8 @@ prop_checkModifiedArithmeticInRedirection3 = verifyNot checkModifiedArithmeticIn
 prop_checkModifiedArithmeticInRedirection4 = verify checkModifiedArithmeticInRedirection "cat <<< $((i++))"
 prop_checkModifiedArithmeticInRedirection5 = verify checkModifiedArithmeticInRedirection "cat << foo\n$((i++))\nfoo\n"
 prop_checkModifiedArithmeticInRedirection6 = verifyNot checkModifiedArithmeticInRedirection "#!/bin/dash\nls > $((i=i+1))"
-checkModifiedArithmeticInRedirection params t = unless (shellType params == Dash) $
+prop_checkModifiedArithmeticInRedirection7 = verifyNot checkModifiedArithmeticInRedirection "#!/bin/busybox sh\ncat << foo\n$((i++))\nfoo\n"
+checkModifiedArithmeticInRedirection params t = unless (shellType params == Dash || shellType params == BusyboxSh) $
     case t of
         T_Redirecting _ redirs (T_SimpleCommand _ _ (_:_)) -> mapM_ checkRedirs redirs
         _ -> return ()
@@ -4356,6 +4359,7 @@ checkEqualsInCommand params originalToken =
             Bash -> errWithFix id 2277 "Use BASH_ARGV0 to assign to $0 in bash (or use [ ] to compare)." bashfix
             Ksh -> err id 2278 "$0 can't be assigned in Ksh (but it does reflect the current function)."
             Dash -> err id 2279 "$0 can't be assigned in Dash. This becomes a command name."
+            BusyboxSh -> err id 2279 "$0 can't be assigned in Busybox Ash. This becomes a command name."
             _ -> err id 2280 "$0 can't be assigned this way, and there is no portable alternative."
     leadingNumberMsg id =
         err id 2282 "Variable names can't start with numbers, so this is interpreted as a command."
diff --git a/src/ShellCheck/AnalyzerLib.hs b/src/ShellCheck/AnalyzerLib.hs
index d864e32af..499082216 100644
--- a/src/ShellCheck/AnalyzerLib.hs
+++ b/src/ShellCheck/AnalyzerLib.hs
@@ -206,18 +206,21 @@ makeParameters spec = params
             case shellType params of
                 Bash -> isOptionSet "lastpipe" root
                 Dash -> False
+                BusyboxSh -> False
                 Sh   -> False
                 Ksh  -> True,
         hasInheritErrexit =
             case shellType params of
                 Bash -> isOptionSet "inherit_errexit" root
                 Dash -> True
+                BusyboxSh -> True
                 Sh   -> True
                 Ksh  -> False,
         hasPipefail =
             case shellType params of
                 Bash -> isOptionSet "pipefail" root
                 Dash -> True
+                BusyboxSh -> isOptionSet "pipefail" root
                 Sh   -> True
                 Ksh  -> isOptionSet "pipefail" root,
         shellTypeSpecified = isJust (asShellType spec) || isJust (asFallbackShell spec),
@@ -899,6 +902,7 @@ isBashLike params =
         Bash -> True
         Ksh -> True
         Dash -> False
+        BusyboxSh -> False
         Sh -> False
 
 isTrueAssignmentSource c =
diff --git a/src/ShellCheck/Checks/Commands.hs b/src/ShellCheck/Checks/Commands.hs
index 691836f42..8be60a772 100644
--- a/src/ShellCheck/Checks/Commands.hs
+++ b/src/ShellCheck/Checks/Commands.hs
@@ -930,7 +930,7 @@ prop_checkTimedCommand2 = verify checkTimedCommand "#!/bin/dash\ntime ( foo; bar
 prop_checkTimedCommand3 = verifyNot checkTimedCommand "#!/bin/sh\ntime sleep 1"
 checkTimedCommand = CommandCheck (Exactly "time") f where
     f (T_SimpleCommand _ _ (c:args@(_:_))) =
-        whenShell [Sh, Dash] $ do
+        whenShell [Sh, Dash, BusyboxSh] $ do
             let cmd = last args -- "time" is parsed with a command as argument
             when (isPiped cmd) $
                 warn (getId c) 2176 "'time' is undefined for pipelines. time single stage or bash -c instead."
@@ -954,7 +954,7 @@ checkTimedCommand = CommandCheck (Exactly "time") f where
 prop_checkLocalScope1 = verify checkLocalScope "local foo=3"
 prop_checkLocalScope2 = verifyNot checkLocalScope "f() { local foo=3; }"
 checkLocalScope = CommandCheck (Exactly "local") $ \t ->
-    whenShell [Bash, Dash] $ do -- Ksh allows it, Sh doesn't support local
+    whenShell [Bash, Dash, BusyboxSh] $ do -- Ksh allows it, Sh doesn't support local
         path <- getPathM t
         unless (any isFunctionLike path) $
             err (getId $ getCommandTokenOrThis t) 2168 "'local' is only valid in functions."
diff --git a/src/ShellCheck/Checks/ShellSupport.hs b/src/ShellCheck/Checks/ShellSupport.hs
index 1f012d24c..7112b9284 100644
--- a/src/ShellCheck/Checks/ShellSupport.hs
+++ b/src/ShellCheck/Checks/ShellSupport.hs
@@ -76,7 +76,7 @@ verifyNot c s = producesComments (testChecker c) s == Just False
 prop_checkForDecimals1 = verify checkForDecimals "((3.14*c))"
 prop_checkForDecimals2 = verify checkForDecimals "foo[1.2]=bar"
 prop_checkForDecimals3 = verifyNot checkForDecimals "declare -A foo; foo[1.2]=bar"
-checkForDecimals = ForShell [Sh, Dash, Bash] f
+checkForDecimals = ForShell [Sh, Dash, BusyboxSh, Bash] f
   where
     f t@(TA_Expansion id _) = sequence_ $ do
         str <- getLiteralString t
@@ -196,14 +196,16 @@ prop_checkBashisms101 = verify checkBashisms "read"
 prop_checkBashisms102 = verifyNot checkBashisms "read -r foo"
 prop_checkBashisms103 = verifyNot checkBashisms "read foo"
 prop_checkBashisms104 = verifyNot checkBashisms "read ''"
-checkBashisms = ForShell [Sh, Dash] $ \t -> do
+prop_checkBashisms105 = verifyNot checkBashisms "#!/bin/busybox sh\nset -o pipefail"
+checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     params <- ask
     kludge params t
  where
   -- This code was copy-pasted from Analytics where params was a variable
   kludge params = bashism
    where
-    isDash = shellType params == Dash
+    isBusyboxSh = shellType params == BusyboxSh
+    isDash = shellType params == Dash || isBusyboxSh
     warnMsg id code s =
         if isDash
         then err  id code $ "In dash, " ++ s ++ " not supported."
@@ -590,7 +592,7 @@ checkPS1Assignments = ForShell [Bash] f
 
 prop_checkMultipleBangs1 = verify checkMultipleBangs "! ! true"
 prop_checkMultipleBangs2 = verifyNot checkMultipleBangs "! true"
-checkMultipleBangs = ForShell [Dash, Sh] f
+checkMultipleBangs = ForShell [Dash, BusyboxSh, Sh] f
   where
     f token = case token of
         T_Banged id (T_Banged _ _) ->
@@ -601,7 +603,7 @@ checkMultipleBangs = ForShell [Dash, Sh] f
 prop_checkBangAfterPipe1 = verify checkBangAfterPipe "true | ! true"
 prop_checkBangAfterPipe2 = verifyNot checkBangAfterPipe "true | ( ! true )"
 prop_checkBangAfterPipe3 = verifyNot checkBangAfterPipe "! ! true | true"
-checkBangAfterPipe = ForShell [Dash, Sh, Bash] f
+checkBangAfterPipe = ForShell [Dash, BusyboxSh, Sh, Bash] f
   where
     f token = case token of
         T_Pipeline _ _ cmds -> mapM_ check cmds

From 00ffd2db33724c31d8857d278379f8140a3f5fce Mon Sep 17 00:00:00 2001
From: Grische <github@grische.xyz>
Date: Sat, 25 Nov 2023 13:50:23 +0100
Subject: [PATCH 3/9] silence SC3010 for busybox sh

---
 src/ShellCheck/Checks/ShellSupport.hs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/ShellCheck/Checks/ShellSupport.hs b/src/ShellCheck/Checks/ShellSupport.hs
index 7112b9284..9ade1c10a 100644
--- a/src/ShellCheck/Checks/ShellSupport.hs
+++ b/src/ShellCheck/Checks/ShellSupport.hs
@@ -197,6 +197,7 @@ prop_checkBashisms102 = verifyNot checkBashisms "read -r foo"
 prop_checkBashisms103 = verifyNot checkBashisms "read foo"
 prop_checkBashisms104 = verifyNot checkBashisms "read ''"
 prop_checkBashisms105 = verifyNot checkBashisms "#!/bin/busybox sh\nset -o pipefail"
+prop_checkBashisms106 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[[ \"$x\" = \"$x\" ]]"
 checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     params <- ask
     kludge params t
@@ -221,7 +222,8 @@ checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     bashism (T_DollarBracket id _) = warnMsg id 3007 "$[..] in place of $((..)) is"
     bashism (T_SelectIn id _ _ _) = warnMsg id 3008 "select loops are"
     bashism (T_BraceExpansion id _) = warnMsg id 3009 "brace expansion is"
-    bashism (T_Condition id DoubleBracket _) = warnMsg id 3010 "[[ ]] is"
+    bashism (T_Condition id DoubleBracket _) =
+        unless isBusyboxSh $ warnMsg id 3010 "[[ ]] is"
     bashism (T_HereString id _) = warnMsg id 3011 "here-strings are"
     bashism (TC_Binary id SingleBracket op _ _)
         | op `elem` [ "<", ">", "\\<", "\\>", "<=", ">=", "\\<=", "\\>="] =

From 903421fb5dff31993c07b8b25eb0d46c388cfba0 Mon Sep 17 00:00:00 2001
From: Grische <github@grische.xyz>
Date: Sat, 25 Nov 2023 13:53:13 +0100
Subject: [PATCH 4/9] silence SC3014 for busybox sh

---
 src/ShellCheck/Checks/ShellSupport.hs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/ShellCheck/Checks/ShellSupport.hs b/src/ShellCheck/Checks/ShellSupport.hs
index 9ade1c10a..e1a09dd49 100644
--- a/src/ShellCheck/Checks/ShellSupport.hs
+++ b/src/ShellCheck/Checks/ShellSupport.hs
@@ -198,6 +198,7 @@ prop_checkBashisms103 = verifyNot checkBashisms "read foo"
 prop_checkBashisms104 = verifyNot checkBashisms "read ''"
 prop_checkBashisms105 = verifyNot checkBashisms "#!/bin/busybox sh\nset -o pipefail"
 prop_checkBashisms106 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[[ \"$x\" = \"$x\" ]]"
+prop_checkBashisms107 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[ \"$x\" == \"$x\" ]"
 checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     params <- ask
     kludge params t
@@ -238,9 +239,9 @@ checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
         | op `elem` [ "-ot", "-nt", "-ef" ] =
             unless isDash $ warnMsg id 3013 $ op ++ " is"
     bashism (TC_Binary id SingleBracket "==" _ _) =
-            warnMsg id 3014 "== in place of = is"
+        unless isBusyboxSh $ warnMsg id 3014 "== in place of = is"
     bashism (T_SimpleCommand id _ [asStr -> Just "test", lhs, asStr -> Just "==", rhs]) =
-            warnMsg id 3014 "== in place of = is"
+        unless isBusyboxSh $ warnMsg id 3014 "== in place of = is"
     bashism (TC_Binary id SingleBracket "=~" _ _) =
             warnMsg id 3015 "=~ regex matching is"
     bashism (T_SimpleCommand id _ [asStr -> Just "test", lhs, asStr -> Just "=~", rhs]) =

From ac63dc33c9b9b3576bc6e3f44049a9e6a53dfaea Mon Sep 17 00:00:00 2001
From: Grische <github@grische.xyz>
Date: Sat, 25 Nov 2023 13:55:07 +0100
Subject: [PATCH 5/9] silence SC3020 for busybox sh

---
 src/ShellCheck/Checks/ShellSupport.hs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/ShellCheck/Checks/ShellSupport.hs b/src/ShellCheck/Checks/ShellSupport.hs
index e1a09dd49..44097513e 100644
--- a/src/ShellCheck/Checks/ShellSupport.hs
+++ b/src/ShellCheck/Checks/ShellSupport.hs
@@ -199,6 +199,7 @@ prop_checkBashisms104 = verifyNot checkBashisms "read ''"
 prop_checkBashisms105 = verifyNot checkBashisms "#!/bin/busybox sh\nset -o pipefail"
 prop_checkBashisms106 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[[ \"$x\" = \"$x\" ]]"
 prop_checkBashisms107 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[ \"$x\" == \"$x\" ]"
+prop_checkBashisms108 = verifyNot checkBashisms "#!/bin/busybox sh\necho magic &> /dev/null"
 checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     params <- ask
     kludge params t
@@ -258,7 +259,8 @@ checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
         | op `elem` [ "|++", "|--", "++|", "--|"] =
             warnMsg id 3018 $ filter (/= '|') op ++ " is"
     bashism (TA_Binary id "**" _ _) = warnMsg id 3019 "exponentials are"
-    bashism (T_FdRedirect id "&" (T_IoFile _ (T_Greater _) _)) = warnMsg id 3020 "&> is"
+    bashism (T_FdRedirect id "&" (T_IoFile _ (T_Greater _) _)) =
+        unless isBusyboxSh $ warnMsg id 3020 "&> is"
     bashism (T_FdRedirect id "" (T_IoFile _ (T_GREATAND _) file)) =
         unless (all isDigit $ onlyLiteralString file) $ warnMsg id 3021 ">& filename (as opposed to >& fd) is"
     bashism (T_FdRedirect id ('{':_) _) = warnMsg id 3022 "named file descriptors are"

From a3b8be82fe2b5d41837463bf81b1a92bb84e3835 Mon Sep 17 00:00:00 2001
From: Grische <github@grische.xyz>
Date: Sat, 25 Nov 2023 13:58:49 +0100
Subject: [PATCH 6/9] silence SC3048 for busybox sh

---
 src/ShellCheck/Checks/ShellSupport.hs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/ShellCheck/Checks/ShellSupport.hs b/src/ShellCheck/Checks/ShellSupport.hs
index 44097513e..6ebdd7060 100644
--- a/src/ShellCheck/Checks/ShellSupport.hs
+++ b/src/ShellCheck/Checks/ShellSupport.hs
@@ -200,6 +200,7 @@ prop_checkBashisms105 = verifyNot checkBashisms "#!/bin/busybox sh\nset -o pipef
 prop_checkBashisms106 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[[ \"$x\" = \"$x\" ]]"
 prop_checkBashisms107 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[ \"$x\" == \"$x\" ]"
 prop_checkBashisms108 = verifyNot checkBashisms "#!/bin/busybox sh\necho magic &> /dev/null"
+prop_checkBashisms109 = verifyNot checkBashisms "#!/bin/busybox sh\ntrap stop EXIT SIGTERM"
 checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     params <- ask
     kludge params t
@@ -399,7 +400,7 @@ checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
                         return $ do
                             when (upper `elem` ["ERR", "DEBUG", "RETURN"]) $
                                 warnMsg (getId token) 3047 $ "trapping " ++ str ++ " is"
-                            when ("SIG" `isPrefixOf` upper) $
+                            when (not isBusyboxSh && "SIG" `isPrefixOf` upper) $
                                 warnMsg (getId token) 3048
                                     "prefixing signal names with 'SIG' is"
                             when (not isDash && upper /= str) $

From ca255fe3263e53c7cb21618eac7d5e52e5c0a665 Mon Sep 17 00:00:00 2001
From: Grische <github@grische.xyz>
Date: Sat, 25 Nov 2023 14:04:11 +0100
Subject: [PATCH 7/9] silence SC3046 and SC3051 for busybox sh

---
 src/ShellCheck/Checks/ShellSupport.hs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/ShellCheck/Checks/ShellSupport.hs b/src/ShellCheck/Checks/ShellSupport.hs
index 6ebdd7060..f4c93fc7e 100644
--- a/src/ShellCheck/Checks/ShellSupport.hs
+++ b/src/ShellCheck/Checks/ShellSupport.hs
@@ -201,6 +201,7 @@ prop_checkBashisms106 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[[ \"$x
 prop_checkBashisms107 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[ \"$x\" == \"$x\" ]"
 prop_checkBashisms108 = verifyNot checkBashisms "#!/bin/busybox sh\necho magic &> /dev/null"
 prop_checkBashisms109 = verifyNot checkBashisms "#!/bin/busybox sh\ntrap stop EXIT SIGTERM"
+prop_checkBashisms110 = verifyNot checkBashisms "#!/bin/busybox sh\nsource /dev/null"
 checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     params <- ask
     kludge params t
@@ -391,7 +392,8 @@ checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
                     (\x -> (not . null . snd $ x) && snd x `notElem` allowed) flags
                 return . warnMsg (getId word) 3045 $ name ++ " -" ++ flag ++ " is"
 
-            when (name == "source") $ warnMsg id 3046 "'source' in place of '.' is"
+            when (name == "source" && not isBusyboxSh) $
+                warnMsg id 3046 "'source' in place of '.' is"
             when (name == "trap") $
                 let
                     check token = sequence_ $ do
@@ -440,7 +442,9 @@ checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
             ("wait", Just [])
             ]
     bashism t@(T_SourceCommand id src _)
-        | getCommandName src == Just "source" = warnMsg id 3051 "'source' in place of '.' is"
+      | getCommandName src == Just "source" =
+          unless isBusyboxSh $
+            warnMsg id 3051 "'source' in place of '.' is"
     bashism (TA_Expansion _ (T_Literal id str : _))
         | str `matches` radix = warnMsg id 3052 "arithmetic base conversion is"
       where

From fdcce458c189848b76d3779e35581cd012af201d Mon Sep 17 00:00:00 2001
From: Grische <github@grische.xyz>
Date: Sat, 25 Nov 2023 15:10:44 +0100
Subject: [PATCH 8/9] silence some shell expansions for busybox sh

---
 src/ShellCheck/Checks/ShellSupport.hs | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/ShellCheck/Checks/ShellSupport.hs b/src/ShellCheck/Checks/ShellSupport.hs
index f4c93fc7e..e652cb57c 100644
--- a/src/ShellCheck/Checks/ShellSupport.hs
+++ b/src/ShellCheck/Checks/ShellSupport.hs
@@ -202,6 +202,15 @@ prop_checkBashisms107 = verifyNot checkBashisms "#!/bin/busybox sh\nx=x\n[ \"$x\
 prop_checkBashisms108 = verifyNot checkBashisms "#!/bin/busybox sh\necho magic &> /dev/null"
 prop_checkBashisms109 = verifyNot checkBashisms "#!/bin/busybox sh\ntrap stop EXIT SIGTERM"
 prop_checkBashisms110 = verifyNot checkBashisms "#!/bin/busybox sh\nsource /dev/null"
+prop_checkBashisms111 = verify checkBashisms "#!/bin/dash\nx='test'\n${x:0:3}" -- SC3057
+prop_checkBashisms112 = verifyNot checkBashisms "#!/bin/busybox sh\nx='test'\n${x:0:3}" -- SC3057
+prop_checkBashisms113 = verify checkBashisms "#!/bin/dash\nx='test'\n${x/st/xt}" -- SC3060
+prop_checkBashisms114 = verifyNot checkBashisms "#!/bin/busybox sh\nx='test'\n${x/st/xt}" -- SC3060
+prop_checkBashisms115 = verify checkBashisms "#!/bin/busybox sh\nx='test'\n${!x}" -- SC3053
+prop_checkBashisms116 = verify checkBashisms "#!/bin/busybox sh\nx='test'\n${x[1]}" -- SC3054
+prop_checkBashisms117 = verify checkBashisms "#!/bin/busybox sh\nx='test'\n${!x[@]}" -- SC3055
+prop_checkBashisms118 = verify checkBashisms "#!/bin/busybox sh\nxyz=1\n${!x*}" -- SC3056
+prop_checkBashisms119 = verify checkBashisms "#!/bin/busybox sh\nx='test'\n${x^^[t]}" -- SC3059
 checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     params <- ask
     kludge params t
@@ -282,7 +291,8 @@ checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
         warnMsg id 3028 $ str ++ " is"
 
     bashism t@(T_DollarBraced id _ token) = do
-        mapM_ check expansion
+        unless isBusyboxSh $ mapM_ check simpleExpansions
+        mapM_ check advancedExpansions
         when (isBashVariable var) $
             warnMsg id 3028 $ var ++ " is"
       where
@@ -452,14 +462,16 @@ checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     bashism _ = return ()
 
     varChars="_0-9a-zA-Z"
-    expansion = let re = mkRegex in [
+    advancedExpansions = let re = mkRegex in [
         (re $ "^![" ++ varChars ++ "]", 3053, "indirect expansion is"),
         (re $ "^[" ++ varChars ++ "]+\\[.*\\]$", 3054, "array references are"),
         (re $ "^![" ++ varChars ++ "]+\\[[*@]]$", 3055, "array key expansion is"),
         (re $ "^![" ++ varChars ++ "]+[*@]$", 3056, "name matching prefixes are"),
+        (re $ "^[" ++ varChars ++ "*@]+(\\[.*\\])?[,^]", 3059, "case modification is")
+        ]
+    simpleExpansions = let re = mkRegex in [
         (re $ "^[" ++ varChars ++ "*@]+:[^-=?+]", 3057, "string indexing is"),
         (re $ "^([*@][%#]|#[@*])", 3058, "string operations on $@/$* are"),
-        (re $ "^[" ++ varChars ++ "*@]+(\\[.*\\])?[,^]", 3059, "case modification is"),
         (re $ "^[" ++ varChars ++ "*@]+(\\[.*\\])?/", 3060, "string replacement is")
         ]
     bashVars = [

From 74282b0a9319bdcc0e3a4a17e2db1969e1c73be2 Mon Sep 17 00:00:00 2001
From: Vidar Holen <vidar@vidarholen.net>
Date: Sun, 10 Dec 2023 17:05:29 -0800
Subject: [PATCH 9/9] Recognize 'busybox' in --shell and directives. Add to doc
 texts.

---
 shellcheck.1.md                       | 3 ++-
 shellcheck.hs                         | 2 +-
 src/ShellCheck/Checks/ShellSupport.hs | 2 ++
 src/ShellCheck/Data.hs                | 1 +
 4 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/shellcheck.1.md b/shellcheck.1.md
index 9675e79ec..89f6d50b6 100644
--- a/shellcheck.1.md
+++ b/shellcheck.1.md
@@ -85,7 +85,8 @@ not warn at all, as `ksh` supports decimals in arithmetic contexts.
 
 **-s**\ *shell*,\ **--shell=***shell*
 
-:   Specify Bourne shell dialect. Valid values are *sh*, *bash*, *dash* and *ksh*.
+:   Specify Bourne shell dialect. Valid values are *sh*, *bash*, *dash*, *ksh*,
+    and *busybox*.
     The default is to deduce the shell from the file's `shell` directive,
     shebang, or `.bash/.bats/.dash/.ksh` extension, in that order. *sh* refers to
     POSIX `sh` (not the system's), and will warn of portability issues.
diff --git a/shellcheck.hs b/shellcheck.hs
index 6be9bb142..6f12238a4 100644
--- a/shellcheck.hs
+++ b/shellcheck.hs
@@ -115,7 +115,7 @@ options = [
         "Specify path when looking for sourced files (\"SCRIPTDIR\" for script's dir)",
     Option "s" ["shell"]
         (ReqArg (Flag "shell") "SHELLNAME")
-        "Specify dialect (sh, bash, dash, ksh)",
+        "Specify dialect (sh, bash, dash, ksh, busybox)",
     Option "S" ["severity"]
         (ReqArg (Flag "severity") "SEVERITY")
         "Minimum severity of errors to consider (error, warning, info, style)",
diff --git a/src/ShellCheck/Checks/ShellSupport.hs b/src/ShellCheck/Checks/ShellSupport.hs
index e652cb57c..d0704972a 100644
--- a/src/ShellCheck/Checks/ShellSupport.hs
+++ b/src/ShellCheck/Checks/ShellSupport.hs
@@ -211,6 +211,8 @@ prop_checkBashisms116 = verify checkBashisms "#!/bin/busybox sh\nx='test'\n${x[1
 prop_checkBashisms117 = verify checkBashisms "#!/bin/busybox sh\nx='test'\n${!x[@]}" -- SC3055
 prop_checkBashisms118 = verify checkBashisms "#!/bin/busybox sh\nxyz=1\n${!x*}" -- SC3056
 prop_checkBashisms119 = verify checkBashisms "#!/bin/busybox sh\nx='test'\n${x^^[t]}" -- SC3059
+prop_checkBashisms120 = verify checkBashisms "#!/bin/sh\n[ x == y ]"
+prop_checkBashisms121 = verifyNot checkBashisms "#!/bin/sh\n# shellcheck shell=busybox\n[ x == y ]"
 checkBashisms = ForShell [Sh, Dash, BusyboxSh] $ \t -> do
     params <- ask
     kludge params t
diff --git a/src/ShellCheck/Data.hs b/src/ShellCheck/Data.hs
index 6a8712316..917142ef0 100644
--- a/src/ShellCheck/Data.hs
+++ b/src/ShellCheck/Data.hs
@@ -156,6 +156,7 @@ shellForExecutable name =
         "sh"    -> return Sh
         "bash"  -> return Bash
         "bats"  -> return Bash
+        "busybox"  -> return BusyboxSh -- Used for directives and --shell=busybox
         "busybox sh"  -> return BusyboxSh
         "busybox ash"  -> return BusyboxSh
         "dash"  -> return Dash