vcmp
v = bsearch(&key, var, sizeof(var)/sizeof(VAR) - 1, sizeof(VAR), vcmp);
static int vcmp(const void *, const void *);
else if (vcmp(_TTYS_WINDOW))
else if (vcmp(_TTYS_GROUP))
return (vcmp(s1, s2));
int vcmp(struct bwstring *s1, struct bwstring *s2);