Implied by /help without being specifically stated is that the random filename evades filenames which already exist. From testing a high number of repetitions, I was unable to find it returning an existing filename.
However, it does not evade strings which were used to create subfolders below $mircdir, as shown by this snippet. This alias is slow, and will create 9 subfolders below $mircdir, but should repeat more than enough times to report several foldername collisions:
//var %digit 1 , %reps 999999 | while (%digit isnum 1-9) { mkdir $+(mirc,%digit,00001.tm_) | inc %digit } | while (%reps) { var %a $tempfn | if (*00001* iswm %a) { echo 4 -a %a $isdir(%a) } | dec %reps }
If my guess is correct, this means the normal usage of temp filenames risks collision with $mircdir\foldernames of this pattern, which might eventually cause rename+delete used by /write to fail. To prevent that potential glitch, users running the above command should also remove those 9 foldernames with:
//var %digit 1 | while (%digit isnum 1-9) { rmdir $+(mirc,%digit,00001.tm_) | inc %digit }
A potential enhancement for this identifier could be having an optional $tempfn(pathname), which defaults as $mircdir, allowing scripts to create not-already-taken filenames within other folders than $mircdir itself.
