ls sort alphabetically
char - ascii is 45
char 9 ascii is 57
so file - sort before 9
but why file 999-a sort after 9999a
$ ls -1
-
9
9999a
999-a
ls sort alphabetically
char - ascii is 45
char 9 ascii is 57
so file - sort before 9
but why file 999-a sort after 9999a
$ ls -1
-
9
9999a
999-a