How environmental variables are handled in Ch?
The environmenal variables in Ch are similar to the environmental variables in Unix shell such as bash and csh, and MS-DOS shell. There are four functions in Ch that can be used to handle environental varaibles. Function putenv() can add an environmental varialble to the system. Given an environmental variable, function getenv() can get its corresponding value. Function remenv() can remove an environmental variable. Function isenv() can test if a symbol is an environmental variable. The interactive command execution below demonstrates their application.
