Question: I need to know the UNIX command for "what is the option to output the version information of `ls`?" I think I could use

```
ls -1

```

but that would list everything.

Answer: 
```
ls --version

```

In most cases for GNU commands, `--version` is used after commands
You can print the footer line of a manual page with

```
PAGER='tail -n1' man command

```

*Most* commands include their version number at the start of this line. In your specific example of `ls`, things can be a bit strange.

For example, on my NetBSD system I see `NetBSD 7.1` in that position, so it simply tells which version of the system it is from. GNU `ls` instead places the coreutils version in that position. The GNU variant also includes a `--version` flag, but it also provides only the overall coreutils version.

---

A commentary on `--version`:

Most if not all GNU software supports being passed a `--version` flag. This does not hold for non-GNU software, which includes the default implementations of most commands on several UNIX-like systems.

Further, because of this tradition the GNU implementation of `echo` does not comply with the POSIX standard, which states (excerpt from the manual):

> 
> Implementations shall not support any options.
> 
> 
>