unix-2.7.2.0: POSIX functionality

System.Posix.Env.ByteString

Description

POSIX environment support

Synopsis

# Environment Variables

getEnv looks up a variable in the environment.

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

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

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

setEnv :: ByteString -> ByteString -> Bool -> IO () Source #

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.

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

# Program arguments

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

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.