static int Paug_load(lua_State *L)
{
    augeas *a = Paug_checkarg(L, 1);
    return pushresult(L, aug_load(a), a, NULL);
}

static int f_flush (lua_State *L) {
  return pushresult(L, fflush(tofile(L)) == 0, NULL);
}

static void io_rename (void)
{
  pushresult(rename(luaL_check_string(1),
                    luaL_check_string(2)) == 0);
}

/*
** function to close 'popen' files
*/
static int io_pclose (lua_State *L) {
  FILE **p = tofilep(L);
  int ok = lua_pclose(L, *p);
  *p = NULL;
  return pushresult(L, ok, NULL);
}

static int io_tmpfile (lua_State *L) {
  FILE **pf = newfile(L);
  *pf = tmpfile();
  return (*pf == NULL) ? pushresult(L, 0, NULL) : 1;
}

static int io_remove (lua_State *L) {
  const char *filename = luaL_checkstring(L, 1);
  SAFE_CHECK_FILE_DATA(L, 1);
  return pushresult(L, remove(filename) == 0, filename);
}

static int io_rename (lua_State *L) {
  return pushresult(L, rename(luaL_check_string(L, 1),
                    luaL_check_string(L, 2)) == 0);
}

static int Pwait(lua_State *L)			/** wait([pid]) */
{
	pid_t pid = luaL_optint(L, 1, -1);
	return pushresult(L, waitpid(pid, NULL, 0), NULL);
}

static int Psetgid(lua_State *L)		/** setgid(name or id) */
{
	return pushresult(L, setgid(mygetgid(L, 1)), NULL);
}

/*
** function to close 'popen' files
*/
static int pipe_close (lua_State *L) {
  FILE **p = tofilep(L);
  int ok = fclose(*p);
  *p = NULL;
  return pushresult(L, ok, NULL);
}

static int Psymlink(lua_State *L)		/** symlink(oldpath,newpath) */
{
	const char *oldpath = luaL_checkstring(L, 1);
	const char *newpath = luaL_checkstring(L, 2);
	return pushresult(L, symlink(oldpath, newpath), NULL);
}

/***
Fork this program.
@function fork
@treturn[1] int `0` in the resulting child process
@treturn[2] int process id of child, in the calling process
@return[3] nil
@treturn[3] string error message
@treturn[3] int errnum
@see fork(2)
@see fork.lua
@see fork2.lua
@usage
  local unistd = require "posix.unistd"

  local pid, errmsg = unistd.fork ()
  if pid == nil then
    error (errmsg)
  elseif pid == 0 then
    print ("in child:", unistd.getpid "pid")
  else
    print (require "posix.sys.wait".wait (pid))
  end
  os.exit ()
*/
static int
Pfork(lua_State *L)
{
	checknargs(L, 0);
	return pushresult(L, fork(), NULL);
}

/***
Get id of foreground process group of terminal *fd*.
@function tcgetpgrp
@int fd the file descriptor of the controlling terminal of the current process
@treturn[1] int id of foreground process group
@return[2] nil
@treturn[2] string error message
@treturn[2] int errnum
@see tcgetpgrp(2)
*/
static int
Ptcgetpgrp(lua_State *L)
{
	int fd = checkint(L, 1);
	return pushresult(L, tcgetpgrp(fd), NULL);
}

/***
Get a message queue identifier
@function msgget
@int key message queue id, or `IPC_PRIVATE` for a new queue
@int[opt=0] flags bitwise OR of zero or more from `IPC_CREAT` and `IPC_EXCL`,
  and access permissions `S_IRUSR`, `S_IWUSR`, `S_IRGRP`, `S_IWGRP`, `S_IROTH`
  and `S_IWOTH` (from @{posix.sys.stat})
@treturn[1] int message queue identifier, if successful
@return[2] nil
@treturn[2] string error message
@treturn[2] int errnum
@see msgget(2)
*/
static int
Pmsgget(lua_State *L)
{
	checknargs (L, 2);
	return pushresult(L, msgget(checkint(L, 1), optint(L, 2, 0)), "msgget");
}

static int io_flush (lua_State *L) {
  SAFE_CHECK_FILE_MOD(L);
  return pushresult(L, fflush(getiofile(L, IO_OUTPUT)) == 0, NULL);
}

static int io_remove (lua_State *L) {
  const char *filename = luaL_checkstring(L, 1);
//  return pushresult(L, remove(filename) == 0, filename);
  return pushresult(L, 0, filename);
}

static int f_flush (lua_State *L) {
  SAFE_CHECK_FILE_MOD(L);
  return pushresult(L, fflush(tofile(L, 1)) == 0, NULL);
}

static int io_rename (lua_State *L) {
  const char *fromname = luaL_checkstring(L, 1);
  const char *toname = luaL_checkstring(L, 2);
//  return pushresult(L, rename(fromname, toname) == 0, fromname);
  return pushresult(L, 0, fromname);
}

static int io_close (lua_State *L) {
  IOCtrl *ctrl = (IOCtrl *)lua_touserdata(L, -1);
  lua_pop(L, 1);  /* remove upvalue */
  return pushresult(L, closefile(L, ctrl, getnonullfile(L, ctrl, 1)));
}

static int Prmdir(lua_State *L)			/** rmdir(path) */
{
	const char *path = luaL_checkstring(L, 1);
	return pushresult(L, rmdir(path), path);
}