Copyright | (c) The University of Glasgow 2002 |
---|---|
License | BSD-style (see the file libraries/base/LICENSE) |
Maintainer | libraries@haskell.org |
Stability | provisional |
Portability | non-portable (requires POSIX) |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
POSIX environment support
Synopsis
- getEnv :: ByteString -> IO (Maybe ByteString)
- getEnvDefault :: ByteString -> ByteString -> IO ByteString
- getEnvironmentPrim :: IO [ByteString]
- getEnvironment :: IO [(ByteString, ByteString)]
- setEnvironment :: [(ByteString, ByteString)] -> IO ()
- putEnv :: ByteString -> IO ()
- setEnv :: ByteString -> ByteString -> Bool -> IO ()
- unsetEnv :: ByteString -> IO ()
- clearEnv :: IO ()
- getArgs :: IO [ByteString]
Environment Variables
:: ByteString | variable name |
-> IO (Maybe ByteString) | variable value |
getEnv
looks up a variable in the environment.
:: ByteString | variable name |
-> ByteString | fallback value |
-> IO ByteString | 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.
:: IO [(ByteString, ByteString)] | [(key,value)] |
getEnvironment
retrieves the entire environment as a
list of (key,value)
pairs.
:: [(ByteString, ByteString)] | [(key,value)] |
-> IO () |
setEnvironment
resets the entire environment to the given list of
(key,value)
pairs.
Since: unix-2.7.3
:: ByteString | "key=value" |
-> IO () |
putEnv
function takes an argument of the form name=value
and is equivalent to setEnv(key,value,True{-overwrite-})
.
:: ByteString | variable name |
-> ByteString | 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.
:: ByteString | variable name |
-> IO () |
The unsetEnv
function deletes all instances of the variable name
from the environment.
Program arguments
getArgs :: IO [ByteString] Source #
Computation getArgs
returns a list of the program's command
line arguments (not including the program name), as ByteString
s.
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.