subenv - substitute environment names in string
char *subenv (s)
char *s;
The function subenv scans the source string s for environment
names in the form of $NAME or ${NAME} and returns a pointer to a
string in which the values of the environment names have been
substituted for the names. If the value of an environment name is
not defined, an empty string is substituted for the name. The
source string s is not changed.
getenv
If the result string is more than 200 characters, it is silently
truncated.
The return value points to static data whose contents are
overwritten by each call.