ENH clean up docs in shell
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-- | Functions for formatting and spawning shell commands
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-- | Functions for formatting and spawning shell commands
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--
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-- TLDR: spawning a "command" in xmonad is complicated for weird reasons, and
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-- this solution is the most sane (for me) given the constraints of the xmonad
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-- codebase.
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--
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-- A few facts about xmonad (and window managers in general):
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-- 1) It is single-threaded (since X is single threaded)
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-- 2) Because of (1), it ignores SIGCHLD, which means any subprocess started
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-- by xmonad will instantly be reaped after spawning. This guarantees the
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-- main thread running the WM will never be blocked.
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--
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-- In general, this means that 'System.Process.waitForProcess' (and similar)
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-- will not work since these call wait() on the child process, which will fail
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-- because the child has already been cleared and thus there is nothing on which
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-- to wait. By extension this also means we don't have access to a child's exit
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-- code.
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--
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-- XMonad and contrib use their own method of spawning subprocesses using the
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-- extremely low-level 'System.Process.Posix' API. See the code for
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-- 'XMonad.Core.spawn' or 'XMonad.Util.Run.safeSpawn'. Specifically, the
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-- sequence is (in terms of the low level Linux API):
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-- 1) call fork()
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-- 2) uninstall signal handlers
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-- 3) call setsid()
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-- 4) start new thing with exec()
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--
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-- In practice, I'm guessing the main reason for 2 and 3 is so that child
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-- processes don't inherit the weird SIGCHLD behavior of xmonad itself. The
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-- setsid thing is one way to guarantee that killing the child thread will also
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-- kill its children (if any). Note that this obviously will not block since
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-- we are calling fork() without wait() (which would throw an error anyways).
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--
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-- What if I actually want the exit code?
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--
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-- The best solution (I can come up with), is to use bracket to uninstall
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-- handlers, run process (with wait), and then reinstall handlers. I can use
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-- this with a much higher-level interface which will make things easier. This
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-- obviously means that if the process is running in the main thread, it needs
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-- to be almost instantaneous (since it actually will be blocking). NOTE: I
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-- shouldn't use this to replace the existing functions in xmonad since
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-- 'spawning' a new process in a non-blocking manner with a higher-level API
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-- will produce lots of Haskell objects that need to be cleaned, and it will be
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-- hard (perhaps impossible) to keep track and deal with these after spawning.
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--
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-- This works, albeit with the cost of using almost every process API in Haskell.
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--
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-- Briefly:
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-- 1) 'System.Process.Posix' (where xmonad lives)
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-- 2) 'System.Process' (wraps 1)
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-- 2) 'System.Process.Typed' (wraps 2, which I prefer for getting exit codes)
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-- 3) 'RIO.Process' (wraps 3, which I prefer at the app level)
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{-# LANGUAGE OverloadedStrings #-}
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{-# LANGUAGE OverloadedStrings #-}
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@ -78,70 +27,108 @@ import qualified System.Process.Typed as P
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import qualified XMonad.Core as X
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import qualified XMonad.Core as X
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import qualified XMonad.Util.Run as XR
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import qualified XMonad.Util.Run as XR
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--------------------------------------------------------------------------------
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-- | Fork a new process and wait for its exit code.
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-- | Opening subshell
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--
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-- https://github.com/xmonad/xmonad/issues/113
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-- This function will work despite xmonad ignoring SIGCHLD.
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--
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-- A few facts about xmonad (and window managers in general):
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-- 1) It is single-threaded (since X is single threaded)
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-- 2) Because of (1), it ignores SIGCHLD, which means any subprocess started
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-- by xmonad will instantly be reaped after spawning. This guarantees the
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-- main thread running the WM will never be blocked.
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--
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-- In general, this means I can't wait for exit codes (since wait() doesn't
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-- work) See https://github.com/xmonad/xmonad/issues/113.
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--
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-- If I want an exit code, The best solution (I can come up with), is to use
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-- bracket to uninstall handlers, run process (with wait), and then reinstall
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-- handlers. I can use this with a much higher-level interface which will make
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-- things easier. This obviously means that if the process is running in the
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-- main thread, it needs to be almost instantaneous. Note if using a high-level
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-- API for this, the process needs to spawn, finish, and be reaped by the
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-- xmonad process all while the signal handlers are 'disabled' (which limits
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-- the functions I can use to those that call waitForProcess).
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--
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-- XMonad and contrib use their own method of spawning subprocesses using the
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-- extremely low-level 'System.Process.Posix' API. See the code for
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-- 'XMonad.Core.spawn' or 'XMonad.Util.Run.safeSpawn'. Specifically, the
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-- sequence is (in terms of the low level Linux API):
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-- 1) call fork()
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-- 2) uninstall signal handlers (to allow wait() to work in subprocesses)
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-- 3) call setsid() (so killing the child will kill its children, if any)
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-- 4) start new thing with exec()
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--
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-- In contrast with high-level APIs like 'System.Process', this will leave no
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-- trailing data structures to clean up, at the cost of being gross to look at
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-- and possibly more error-prone.
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runProcess :: P.ProcessConfig a b c -> IO ExitCode
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runProcess = withDefaultSignalHandlers . P.runProcess
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-- | Run an action without xmonad's signal handlers.
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withDefaultSignalHandlers :: IO a -> IO a
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withDefaultSignalHandlers :: IO a -> IO a
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withDefaultSignalHandlers =
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withDefaultSignalHandlers =
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bracket_ X.uninstallSignalHandlers X.installSignalHandlers
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bracket_ X.uninstallSignalHandlers X.installSignalHandlers
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-- | Set a child process to create a new group and session
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addGroupSession :: P.ProcessConfig x y z -> P.ProcessConfig x y z
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addGroupSession :: P.ProcessConfig x y z -> P.ProcessConfig x y z
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addGroupSession = P.setCreateGroup True . P.setNewSession True
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addGroupSession = P.setCreateGroup True . P.setNewSession True
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runProcess :: P.ProcessConfig a b c -> IO ExitCode
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-- | Create a 'ProcessConfig' for a shell command
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runProcess = withDefaultSignalHandlers . P.runProcess
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shell :: T.Text -> P.ProcessConfig () () ()
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shell :: T.Text -> P.ProcessConfig () () ()
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shell = addGroupSession . P.shell . T.unpack
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shell = addGroupSession . P.shell . T.unpack
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-- | Create a 'ProcessConfig' for a command with arguments
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proc :: FilePath -> [T.Text] -> P.ProcessConfig () () ()
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proc :: FilePath -> [T.Text] -> P.ProcessConfig () () ()
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proc cmd args = addGroupSession $ P.proc cmd (T.unpack <$> args)
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proc cmd args = addGroupSession $ P.proc cmd (T.unpack <$> args)
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-- | Run 'XMonad.Core.spawn' with 'Text' input.
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spawn :: MonadIO m => T.Text -> m ()
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spawn :: MonadIO m => T.Text -> m ()
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spawn = X.spawn . T.unpack
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spawn = X.spawn . T.unpack
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-- spawnAt :: MonadIO m => FilePath -> T.Text -> m ()
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-- | Run 'XMonad.Run.Utils.spawnPipe' with 'Text' input.
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-- spawnAt fp = liftIO . void . startProcess . P.setWorkingDir fp . shell
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spawnPipe :: MonadIO m => T.Text -> m Handle
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spawnPipe :: MonadIO m => T.Text -> m Handle
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spawnPipe = XR.spawnPipe . T.unpack
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spawnPipe = XR.spawnPipe . T.unpack
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-- | Run 'XMonad.Core.spawn' with a command and arguments
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spawnCmd :: MonadIO m => FilePath -> [T.Text] -> m ()
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spawnCmd :: MonadIO m => FilePath -> [T.Text] -> m ()
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spawnCmd cmd = spawn . fmtCmd cmd
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spawnCmd cmd = spawn . fmtCmd cmd
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--------------------------------------------------------------------------------
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-- | Format a command and list of arguments as 'Text'
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-- | Formatting commands
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fmtCmd :: FilePath -> [T.Text] -> T.Text
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fmtCmd :: FilePath -> [T.Text] -> T.Text
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fmtCmd cmd args = T.unwords $ T.pack cmd : args
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fmtCmd cmd args = T.unwords $ T.pack cmd : args
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op :: T.Text -> T.Text -> T.Text -> T.Text
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op :: T.Text -> T.Text -> T.Text -> T.Text
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op a x b = T.unwords [a, x, b]
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op a x b = T.unwords [a, x, b]
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-- | Format two shell expressions separated by "&&"
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(#!&&) :: T.Text -> T.Text -> T.Text
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(#!&&) :: T.Text -> T.Text -> T.Text
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cmdA #!&& cmdB = op cmdA "&&" cmdB
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cmdA #!&& cmdB = op cmdA "&&" cmdB
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infixr 0 #!&&
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infixr 0 #!&&
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-- | Format two shell expressions separated by "|"
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(#!|) :: T.Text -> T.Text -> T.Text
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(#!|) :: T.Text -> T.Text -> T.Text
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cmdA #!| cmdB = op cmdA "|" cmdB
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cmdA #!| cmdB = op cmdA "|" cmdB
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infixr 0 #!|
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infixr 0 #!|
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-- | Format two shell expressions separated by "||"
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(#!||) :: T.Text -> T.Text -> T.Text
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(#!||) :: T.Text -> T.Text -> T.Text
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cmdA #!|| cmdB = op cmdA "||" cmdB
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cmdA #!|| cmdB = op cmdA "||" cmdB
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infixr 0 #!||
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infixr 0 #!||
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-- | Format two shell expressions separated by ";"
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(#!>>) :: T.Text -> T.Text -> T.Text
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(#!>>) :: T.Text -> T.Text -> T.Text
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cmdA #!>> cmdB = op cmdA ";" cmdB
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cmdA #!>> cmdB = op cmdA ";" cmdB
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infixr 0 #!>>
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infixr 0 #!>>
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-- | Wrap input in double quotes
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doubleQuote :: T.Text -> T.Text
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doubleQuote :: T.Text -> T.Text
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doubleQuote s = T.concat ["\"", s, "\""]
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doubleQuote s = T.concat ["\"", s, "\""]
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-- | Wrap input in single quotes
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singleQuote :: T.Text -> T.Text
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singleQuote :: T.Text -> T.Text
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singleQuote s = T.concat ["'", s, "'"]
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singleQuote s = T.concat ["'", s, "'"]
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