Distribution.Simple.Utils

:: String	a description of the action we were attempting
-> IO ()	the action itself
-> IO ()
Perform an IO action, catching any IO exceptions and printing an error if one occurs.

breaks :: (a -> Bool) -> [a] -> [[a]]

running programs

rawSystemExit :: Verbosity -> FilePath -> [String] -> IO ()

rawSystemStdout :: Verbosity -> FilePath -> [String] -> IO String

Run a command and return its output.

The output is assumed to be encoded as UTF8.

rawSystemStdout' :: Verbosity -> FilePath -> [String] -> IO (String, ExitCode)

maybeExit :: IO ExitCode -> IO ()

xargs :: Int -> ([String] -> IO ()) -> [String] -> [String] -> IO ()

Like the unix xargs program. Useful for when we've got very long command lines that might overflow an OS limit on command line length and so you need to invoke a command multiple times to get all the args in.

Use it with either of the rawSystem variants above. For example:

 xargs (32*1024) (rawSystemExit verbosity) prog fixedArgs bigArgs

inDir :: Maybe FilePath -> IO () -> IO ()

Executes the action in the specified directory.

copying files

smartCopySources

:: Verbosity	verbosity
-> [FilePath]	build prefix (location of objects)
-> FilePath	Target directory
-> [String]	Modules
-> [String]	search suffixes
-> IO ()
Copy the source files into the right directory. Looks in the build prefix for files that look like the input modules, based on the input search suffixes. It copies the files into the target directory.

createDirectoryIfMissingVerbose :: Verbosity -> Bool -> FilePath -> IO ()

copyFileVerbose :: Verbosity -> FilePath -> FilePath -> IO ()

copyDirectoryRecursiveVerbose :: Verbosity -> FilePath -> FilePath -> IO ()

copyFiles :: Verbosity -> FilePath -> [(FilePath, FilePath)] -> IO ()

Copies a bunch of files to a target directory, preserving the directory structure in the target location. The target directories are created if they do not exist.

The files are identified by a pair of base directory and a path relative to that base. It is only the relative part that is preserved in the destination.

For example:

 copyFiles normal "dist/src"
    [("", "src/Foo.hs"), ("dist/build/", "src/Bar.hs")]

This would copy "src/Foo.hs" to "dist/src/src/Foo.hs" and copy "dist/build/src/Bar.hs" to "dist/src/src/Bar.hs".

This operation is not atomic. Any IO failure during the copy (including any missing source files) leaves the target in an unknown state so it is best to use it with a freshly created directory so that it can be simply deleted if anything goes wrong.

file names

currentDir :: FilePath

The path name that represents the current directory. In Unix, it's ".", but this is system-specific. (E.g. AmigaOS uses the empty string "" for the current directory.)

dotToSep :: String -> String

finding files

findFile

:: [FilePath]	search locations
-> FilePath	File Name
-> IO FilePath

findFileWithExtension :: [String] -> [FilePath] -> FilePath -> IO (Maybe FilePath)

findFileWithExtension' :: [String] -> [FilePath] -> FilePath -> IO (Maybe (FilePath, FilePath))

temp files and dirs

withTempFile

:: FilePath	Temp dir to create the file in
-> String	File name template. See `openTempFile`.
-> (FilePath -> Handle -> IO a)
-> IO a
Use a temporary filename that doesn't already exist.

withTempDirectory :: Verbosity -> FilePath -> IO a -> IO a

Use a temporary directory.

Use this exact given dir which must not already exist.

.cabal and .buildinfo files

defaultPackageDesc :: Verbosity -> IO FilePath

Package description file (pkgname.cabal)

findPackageDesc

:: FilePath	Where to look
-> IO FilePath	pkgname.cabal
Find a package description file in the given directory. Looks for `.cabal` files.

defaultHookedPackageDesc :: IO (Maybe FilePath)

Optional auxiliary package information file (pkgname.buildinfo)

findHookedPackageDesc

:: FilePath	Directory to search
-> IO (Maybe FilePath)	dir`/`pkgname`.buildinfo`, if present
Find auxiliary package information in the given directory. Looks for `.buildinfo` files.

reading and writing files safely

withFileContents :: FilePath -> (String -> IO a) -> IO a

Gets the contents of a file, but guarantee that it gets closed.

The file is read lazily but if it is not fully consumed by the action then the remaining input is truncated and the file is closed.

writeFileAtomic :: FilePath -> String -> IO ()

Writes a file atomically.

The file is either written sucessfully or an IO exception is raised and the original file is left unchanged.

Warning: On Windows this operation is very nearly but not quite atomic. See below.

On Posix it works by writing a temporary file and atomically renaming over the top any pre-existing target file with the temporary one.

On Windows it is not possible to rename over an existing file so the target file has to be deleted before the temporary file is renamed to the target. Therefore there is a race condition between the existing file being removed and the temporary file being renamed. Another thread could write to the target or change the permission on the target directory between the deleting and renaming steps. An exception would be raised but the target file would either no longer exist or have the content as written by the other thread.

On windows it is not possible to delete a file that is open by a process. This case will give an IO exception but the atomic property is not affected.

Unicode

fromUTF8 :: String -> String

toUTF8 :: String -> String

readUTF8File :: FilePath -> IO String

Reads a UTF8 encoded text file as a Unicode String

Reads lazily using ordinary readFile.

withUTF8FileContents :: FilePath -> (String -> IO a) -> IO a

Reads a UTF8 encoded text file as a Unicode String

Same behaviour as withFileContents.

writeUTF8File :: FilePath -> String -> IO ()

Writes a Unicode String as a UTF8 encoded text file.

Uses writeFileAtomic, so provides the same guarantees.

generic utils

equating :: Eq a => (b -> a) -> b -> b -> Bool

comparing :: Ord a => (b -> a) -> b -> b -> Ordering

isInfixOf :: String -> String -> Bool

intercalate :: [a] -> [[a]] -> [a]

lowercase :: String -> String

wrapText :: String -> String

Wraps text to the default line width. Existing newlines are preserved.

wrapLine :: Int -> [String] -> [[String]]

Wraps a list of words to a list of lines of words of a particular width.

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