Cannot write with sysfile_write or sysfile_writetextfile

Hi, I'm trying to write a file using the routine in the documentation, and the external builds ok, but when it is sent the filename, though it creates a file with that name, the file is always containing zero bytes. It cannot write the data/text in the created file. (Btw, when I use sysfile_write, it crashes Max. I even tried to resort to general methods with stdio.h: FILE *fp and fopen/fwrite/fclose, but they are ineffective.)

I did these:

/////among prototypes:

void fthing_write(t_fthing *x, t_symbol *s);
void fthing_dowrite(t_fthing *x, t_symbol *s);

/////inside ext_main:

class_addmethod(c, (method)fthing_write, "write", A_DEFSYM, 0);

/////

void fthing_write(t_fthing *x, t_symbol *s)
{
defer(x, (method)fthing_dowrite, s, 0, NULL);
}

void fthing_dowrite(t_fthing *x, t_symbol *s)
{
char filename[MAX_FILENAME_CHARS];
short path = path_getdefault();
char *buf = "write me into a file";
long err;
t_filehandle fh;

strcpy(filename, s->s_name);

err = path_createsysfile(filename, path, 'TEXT', &fh);
if (err)
{
post("could not create file");
return;
}

err = sysfile_writetextfile(fh, &buf, TEXT_LB_NATIVE);
post("%ld", err); //err shows 0.
sysfile_close(fh);
}

Any help to find out what's missing here?