const size_t len = strlen (name);
unsetenv (const char *name){  const size_t len = strlen (name);  char **ep;  ep = __environ;  while (*ep != NULL)    if (!strncmp (*ep, name, len) && (*ep)[len] == '=')      {	/* Found it.  Remove this pointer by moving later ones back.  */	char **dp = ep;	do	  dp[0] = dp[1];	while (*dp++);	/* Continue the loop in case NAME appears again.  */      }    else      ++ep;  return 0;}