Haskell Hierarchical Libraries (unix package) Contents Index

System.Posix.Env Portability non-portable (requires POSIX) Stability provisional Maintainer libraries@haskell.org

Description

POSIX environment support

Synopsis

getEnv :: String -> IO (Maybe String) getEnvDefault :: String -> String -> IO String getEnvironmentPrim :: IO [String] getEnvironment :: IO [(String, String)] putEnv :: String -> IO () setEnv :: String -> String -> Bool -> IO () unsetEnv :: String -> IO ()

Documentation

getEnv :: String -> IO (Maybe String)

getEnv looks up a variable in the environment.

getEnvDefault :: String -> String -> IO String

getEnvDefault is a wrapper around getEnvVar where the programmer can specify a fallback if the variable is not found in the environment.

getEnvironmentPrim :: IO [String]

getEnvironment :: IO [(String, String)]

getEnvironment retrieves the entire environment as a list of (key,value) pairs.

putEnv :: String -> IO ()

putEnv function takes an argument of the form name=value and is equivalent to setEnv(key,value,True{-overwrite-}).

setEnv :: String -> String -> Bool -> IO ()

The setenv function inserts or resets the environment variable name in the current environment list. If the variable name does not exist in the list, it is inserted with the given value. If the variable does exist, the argument overwrite is tested; if overwrite is False, the variable is not reset, otherwise it is reset to the given value.

unsetEnv :: String -> IO ()

The unsetenv function deletes all instances of the variable name from the environment.

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