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documentation:
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------------------------------------------------------------------------------
--- Library to support operations related to the program execution path,
--- i.e., environment variable `PATH`.
---
--- @author Michael Hanus
--- @version November 2018
------------------------------------------------------------------------------
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sourcecode:
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module System.Path
( dirsInPath, fileInPath, getFileInPath )
where
import System.Directory ( doesFileExist, getAbsolutePath )
import System.FilePath ( (</>), searchPathSeparator )
import System.Environment ( getEnv )
import Data.List ( split )
--- Returns the list of the directories of the environment variable `PATH`.
dirsInPath :: IO [String]
dirsInPath = do
path <- getEnv "PATH"
return $ split (== searchPathSeparator) path
--- Checks whether a file exists in one of the directories
--- of the environment variable `PATH`.
fileInPath :: String -> IO Bool
fileInPath file = do
dirs <- dirsInPath
or <$> mapM (doesFileExist . (</> file)) dirs
--- Checks whether a file exists in one of the directories
--- of the environment variable `PATH` and returns its absolute path,
--- otherwise returns `Nothing`.
getFileInPath :: String -> IO (Maybe String)
getFileInPath file = dirsInPath >>= checkPath
where
checkPath [] = return Nothing
checkPath (dir:dirs) = do
let dirfile = dir </> file
direx <- doesFileExist dirfile
if direx then getAbsolutePath dirfile >>= return . Just
else checkPath dirs
------------------------------------------------------------------------------
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