char *getenv(name) char *name; void setenv(name, value) char *name, *value; void unsetenv(name) char *name;
Setenv searches the environment list as getenv does; if the string name is not found, a string of the form name=value is added to the environment. If it is found, its value is changed to value.
Unsetenv removes all occurrences of the string name from the environment. There is no library provision for completely removing the current environment. It is suggested that the following code be used to do so.
static char *envinit[1];
extern char **environ;
environ = envinit;