Many functions that perform file operations accept either open or closed streams as arguments; see Section 21.1.3 (Stream Arguments to Standardized Functions).
Of these, the functions in the next figure treat open and closed streams differently.
delete-file file-author probe-file directory file-write-date truename
Figure 20-2. File Functions that Treat Open and Closed Streams Differently
Since treatment of open streams by the file system may vary considerably between implementations, however, a closed stream might be the most reliable kind of argument for some of these functions---in particular, those in the next figure. For example, in some file systems, open files are written under temporary names and not renamed until closed and/or are held invisible until closed. In general, any code that is intended to be portable should use such functions carefully.
directory probe-file truename
Figure 20-3. File Functions where Closed Streams Might Work Best