unix-2.8.0.0: POSIX functionality

System.Posix.Env.PosixString

Description

POSIX environment support

Synopsis

# Environment Variables

Arguments

 :: PosixString variable name -> IO (Maybe PosixString) variable value

getEnv looks up a variable in the environment.

Arguments

 :: PosixString variable name -> PosixString fallback value -> IO PosixString variable value or fallback value

getEnvDefault is a wrapper around getEnv where the programmer can specify a fallback as the second argument, which will be used if the variable is not found in the environment.

Arguments

 :: IO [(PosixString, PosixString)] [(key,value)]

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

Arguments

 :: [(PosixString, PosixString)] [(key,value)] -> IO ()

setEnvironment resets the entire environment to the given list of (key,value) pairs.

Arguments

 :: PosixString "key=value" -> IO ()

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

Arguments

 :: PosixString variable name -> PosixString variable value -> Bool overwrite -> 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.

Arguments

 :: PosixString variable name -> IO ()

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

The clearEnv function clears the environment of all name-value pairs.

# Program arguments

Computation getArgs returns a list of the program's command line arguments (not including the program name), as PosixStrings.

Unlike getArgs, this function does no Unicode decoding of the arguments; you get the exact bytes that were passed to the program by the OS. To interpret the arguments as text, some Unicode decoding should be applied.