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

int putenv(const char *string) {
  size_t len;
  int envc;
  int remove=0;
  char *tmp;
  const char **ep;
  char **newenv;
  static char **origenv;
  if (!origenv) origenv=environ;
  if (!(tmp=strchr(string,'='))) {
    len=strlen(string);
    remove=1;
  } else
    len=tmp-string;
  for (envc=0, ep=(const char**)environ; (ep && *ep); ++ep) {
    if (*string == **ep &&
	!memcmp(string,*ep,len) &&
	(*ep)[len]=='=') {
      if (remove) {
	for (; ep[1]; ++ep) ep[0]=ep[1];
	ep[0]=0;
	return 0;
      }
      *ep=string;
      return 0;
    }
    ++envc;
  }
  if (tmp) {
    newenv = (char**) realloc(environ==origenv?0:environ,
			      (envc+2)*sizeof(char*));
    if (!newenv) return -1;
    if (envc && (environ==origenv)) {
      memcpy(newenv,origenv,envc*sizeof(char*));
    }
    newenv[envc]=(char*)string;
    newenv[envc+1]=0;
    environ=newenv;
  }
  return 0;
}