scc

 1#include <errno.h>
 2#include <stdlib.h>
 3#include <string.h>
 4
 5extern char **_environ;
 6
 7int
 8putenv(char *name)
 9{
10	char **p, *s;
11	size_t siz, len, cnt;
12	static char **lastenv;
13
14	if ((s = strchr(name, '=')) == NULL) {
15		errno = EINVAL;
16		return -1;
17	}
18	len = s - name;
19
20	for (p = _environ; *p; ++p) {
21		if (!strncmp(name, *p, len) && (*p)[len] == '=') {
22			*p = name;
23			return 0;
24		}
25	}
26
27	cnt = p - _environ;
28	siz = (cnt + 2) * sizeof(char **);
29
30	if ((p = realloc(lastenv, siz)) == NULL)
31		return -1;
32	if (!lastenv)
33		memcpy(p, _environ, cnt * sizeof(char **));
34	lastenv = _environ = p;
35
36	p[cnt] = name;
37	p[cnt+1] = NULL;
38
39	return 0;
40}