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/*
 * Copyright (c) 2010 Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <config.h>

#include <sys/types.h>

#include <stdio.h>
#ifdef STDC_HEADERS
# include <stdlib.h>
# include <stddef.h>
#else
# ifdef HAVE_STDLIB_H
#  include <stdlib.h>
# endif
#endif /* STDC_HEADERS */
#ifdef HAVE_STRING_H
# include <string.h>
#endif /* HAVE_STRING_H */
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif /* HAVE_STRINGS_H */
#include <errno.h>

#include "missing.h"

extern char **environ;	/* global environment */

#ifdef UNSETENV_VOID
void
#else
int
#endif
unsetenv(const char *var)
{
    char **ep = environ;
    size_t len;

    if (var == NULL || *var == '\0' || strchr(var, '=') != NULL) {
	errno = EINVAL;
#ifdef UNSETENV_VOID
	return;
#else
	return -1;
#endif
    }

    len = strlen(var);
    while (*ep != NULL) {
	if (strncmp(var, *ep, len) == 0 && (*ep)[len] == '=') {
	    /* Found it; shift remainder + NULL over by one. */
	    char **cur = ep;
	    while ((*cur = *(cur + 1)) != NULL)
		cur++;
	    /* Keep going, could be multiple instances of the var. */
	} else {
	    ep++;
	}
    }
#ifndef UNSETENV_VOID
    return 0;
#endif
}