unique-filename
===============

Generate a unique filename for use in temporary directories or caches.

```js
const uniqueFilename = require('unique-filename')

// returns something like: '/tmp/c5b28f47'
const randomTmpfile = uniqueFilename(os.tmpdir())

// returns something like: '/tmp/my-test-51a7b48d'
const randomPrefixedTmpfile = uniqueFilename(os.tmpdir(), 'my-test')

// returns something like: '/my-tmp-dir/testing-7ddd44c0'
const uniqueTmpfile = uniqueFilename('/my-tmp-dir', 'testing', '/my/thing/to/uniq/on')
```

### uniqueFilename(*dir*, *fileprefix*, *uniqstr*) → String

Returns the full path of a unique filename that looks like:
`dir/prefix-7ddd44c0`
or `dir/7ddd44c0`

*dir* – The path you want the filename in. `os.tmpdir()` is a good choice for this.

*fileprefix* – A string to append prior to the unique part of the filename.
The parameter is required if *uniqstr* is also passed in but is otherwise
optional and can be `undefined`/`null`/`''`. If present and not empty
then this string plus a hyphen are prepended to the unique part.

*uniqstr* – Optional, if not passed the unique part of the resulting
filename will be random.  If passed in it will be generated from this string
in a reproducible way.