CosmOS
> dir
one.txt                 13
two.txt                 14
2 files
> rename one.txt first.txt
renamed
> dir
first.txt               13
two.txt                 14
2 files
> delete first.txt
gone
> dir
two.txt                 14
1 file
> delete first.txt
no such file
> rename two.txt
rename what to what?
> rename two.txt two.txt
there is no such file, or that name is taken
> exit
halted
Execution halted.
[exit 0]