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GHC 10.0.0.20260917 · lts/ghc-10.0.x · 04404a6 · 2026-10-19

Moduleunix-2.8.8.0Haskell2010

System.Posix.Env

POSIX environment support

Synopsis

value getEnv
value getEnvDefault
value getEnvironmentPrim
value getEnvironment
value setEnvironment
value putEnv
value setEnv
value unsetEnv
value clearEnv

Packageunix-2.8.8.0
Exports9
LanguageHaskell2010
LicenceBSD-3-Clause
SourceEnv.hsc

valuegetEnv

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

getEnv looks up a variable in the environment.

valuegetEnvDefault

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

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

valuegetEnvironmentPrim :: IO [String]

valuegetEnvironment

:: IO [(String, String)]
```
[(key,value)]
```

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

valuesetEnvironment

:: [(String, String)]
```
[(key,value)]
```
-> IO ()

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

valueputEnv

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

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

valuesetEnv

:: String
variable name
-> String
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.

valueunsetEnv

:: String
variable name
-> IO ()

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

valueclearEnv :: IO ()

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