I'm running a command from a script like

```
tar -c -f ar.tar a b c d

```

where b, c, and d may not exist, and may be directories. The solutions that I've come up with are piping the output of `ls -d` to `grep`, then splicing it into the `tar` command, or turning on extended globs for `@(a|b|c|d)`.

Is there a neater way of doing this? I'm on Debian Wheezy, which doesn't seem to have an `--include` parameter.