1#include <sys.h>23#include <stdlib.h>4#include <string.h>56#undef getenv78char *9getenv(const char *name)10{11 char **p, *s;12 size_t len = strlen(name);1314 for (p = _environ; s = *p; ++p) {15 if (!strncmp(name, s, len) && s[len] == '=')16 return s + len + 1;17 }18 return NULL;19}