System.Environment

haskell2010-1.1.2.0: Compatibility with Haskell 2010

Safe Haskell | Safe
Language | Haskell2010

System.Environment

Synopsis

- getArgs :: IO [String]
- getProgName :: IO String
- getEnv :: String -> IO String

# Documentation

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.

getEnv :: String -> IO String Source

Computation `getEnv` `var` returns the value of the environment variable `var`. For the inverse, POSIX users can use `putEnv`.

This computation may fail with:

- `isDoesNotExistError` if the environment variable does not exist.