findenv
if ((p = findenv(my_environ, string, 0, &value)) != NULL) {
if ((p = findenv(my_environ, name, 1, &value)) != NULL) {
if (findenv(_environ, name, 1, &value) != NULL)
while (findenv(name, &offset)) /*%< if set multiple times */
static char *findenv(const char *name, int *offset);
if ((c = findenv(name, &offset))) { /*%< find if already exists */