File Operations on Open and Closed Streams (ANSI and GNU Common Lisp Document)

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#### 20.1.2 File Operations on Open and Closed Streams

Many functions that perform file operations accept either open or closed streams as arguments; see Stream Arguments to Standardized Functions.

Of these, the functions in Figure 20–2 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 Figure 20–3. 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