| Copyright | (c) Habib Alamin 2017 |
|---|---|
| License | BSD-style (see the file libraries/base/LICENSE) |
| Maintainer | libraries@haskell.org |
| Stability | provisional |
| Portability | portable |
| Safe Haskell | Safe |
| Language | Haskell2010 |
System.Environment.Blank
Description
A setEnv implementation that allows blank environment variables. Mimics
the Env module from the unix package, but with support
for Windows too.
The matrix of platforms that:
- support
putenv(FOO)to unset environment variables, - support
putenv("FOO=")to unset environment variables or set them to blank values, - support
unsetenvto unset environment variables, - support
setenvto set environment variables, - etc.
is very complicated. Some platforms don't support unsetting of environment variables at all.
Synopsis
- getExecutablePath :: IO FilePath
- getArgs :: IO [String]
- getProgName :: IO String
- withArgs :: [String] -> IO a -> IO a
- withProgName :: String -> IO a -> IO a
- getEnvironment :: IO [(String, String)]
- getEnv :: String -> IO (Maybe String)
- getEnvDefault :: String -> String -> IO String
- setEnv :: String -> String -> Bool -> IO ()
- unsetEnv :: String -> IO ()
Documentation
getExecutablePath :: IO FilePath Source #
Returns the absolute pathname of the current executable.
Note that for scripts and interactive sessions, this is the path to the interpreter (e.g. ghci.)
Since base 4.11.0.0, getExecutablePath resolves symlinks on Windows.
If an executable is launched through a symlink, getExecutablePath
returns the absolute path of the original executable.
Since: base-4.6.0.0
getArgs :: IO [String] Source #
Computation getArgs returns a list of the program's command
line arguments (not including the program name).
getProgName :: IO String Source #
Computation getProgName returns the name of the program as it was
invoked.
However, this is hard-to-impossible to implement on some non-Unix
OSes, so instead, for maximum portability, we just return the leafname
of the program as invoked. Even then there are some differences
between platforms: on Windows, for example, a program invoked as foo
is probably really FOO.EXE, and that is what getProgName will return.
withProgName :: String -> IO a -> IO a Source #
withProgName name act - while executing action act,
have getProgName return name.
getEnvironment :: IO [(String, String)] Source #
getEnvironment retrieves the entire environment as a
list of (key,value) pairs.
If an environment entry does not contain an '=' character,
the key is the whole entry and the value is the empty string.
Arguments
| :: String | variable name |
| -> String | fallback value |
| -> IO String | variable value or fallback value |
Get an environment value or a default value.