getenv
getenv — retrieves the value of an environment variable.
getenv (envar)
envarA string.
A string containing the value of the given environment variable, or nil if the environment
variable is not defined.
This function retrieves the value of an environment variable from the
current process's environment. The environment variable must have been set
or defined previously by a call to setenv.
Gamma>setenv("high", "40");tGamma>getenv("high");"40"Gamma>low = 20;20Gamma>getenv("low");nilGamma>