Function Reference
— Built-in Function: tmpnam (dir, prefix)

Return a unique temporary file name as a string.

If prefix is omitted, a value of "oct-" is used. If dir is also omitted, the default directory for temporary files is used. If dir is provided, it must exist, otherwise the default directory for temporary files is used. Since the named file is not opened, by tmpnam, it is possible (though relatively unlikely) that it will not be available by the time your program attempts to open it.