#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "libc.h"

char *__strchrnul(const char *, int);

static void dummy(char *p, char *r) {}
weak_alias(dummy, __env_change);

int unsetenv(const char *name)
{
	size_t l = __strchrnul(name, '=') - name;
	if (!l || name[l]) {
		errno = EINVAL;
		return -1;
	}
	if (!__environ) return 0;
	for (char **e = __environ; *e; e++)
		while (*e && !strncmp(name, *e, l) && l[*e] == '=') {
			char **ee = e, *tmp = *e;
			do *ee = *(ee+1);
			while (*++ee);
			__env_change(tmp, 0);
		}
	return 0;
}