FileUtil.GetUniqueTempPathInProject  

static function GetUniqueTempPathInProject () : String

Description

Returns a unique path in the Temp folder within your current project.

The returned path is relative to the project folder.

The returned path is of a form Temp/UnityTempFile-uniqueID, where uniqueID is guaranteed to be unique over space and time.

You can use it to create temporary files/folders and be sure that you are not overriding somebody else's files, plus you don't have to keep track of the unique IDs yourself.

@MenuItem ("Example/Get Unique Path")
static function GetUniqueProjectPath () {
    // Prints the unique path
    Debug.Log (FileUtil.GetUniqueTempPathInProject ());
}