25.6.3 Truenames

The truename of a file is the name that you get by following symbolic links at all levels until none remain, then simplifying away ‘.’ and ‘..’ appearing as name components. This results in a sort of canonical name for the file. A file does not always have a unique truename; the number of distinct truenames a file has is equal to the number of hard links to the file. However, truenames are useful because they eliminate symbolic links as a cause of name variation.

Function: file-truename filename

The function file-truename returns the truename of the file filename. The argument must be an absolute file name.

This function does not expand environment variables. Only substitute-in-file-name does that. Voir Definition of substitute-in-file-name.

If you may need to follow symbolic links preceding ‘..’ appearing as a name component, you should make sure to call file-truename without prior direct or indirect calls to expand-file-name, as otherwise the file name component immediately preceding ‘..’ will be “simplified away” before file-truename is called. To eliminate the need for a call to expand-file-name, file-truename handles ‘~’ in the same way that expand-file-name does. Voir la section Functions that Expand Filenames.

Function: file-chase-links filename &optional limit

This function follows symbolic links, starting with filename, until it finds a file name which is not the name of a symbolic link. Then it returns that file name. This function does not follow symbolic links at the level of parent directories.

If you specify a number for limit, then after chasing through that many links, the function just returns what it has even if that is still a symbolic link.

To illustrate the difference between file-chase-links and file-truename, suppose that ‘/usr/foo’ is a symbolic link to the directory ‘/home/foo’, and ‘/home/foo/hello’ is an ordinary file (or at least, not a symbolic link) or nonexistent. Then we would have:

(file-chase-links "/usr/foo/hello")
     ;; This does not follow the links in the parent directories.
     ⇒ "/usr/foo/hello"
(file-truename "/usr/foo/hello")
     ;; Assuming that ‘/home’ is not a symbolic link.
     ⇒ "/home/foo/hello"

Voir la section Buffer File Name, for related information.

Ce document a été généré par Eric Reinbold le 13 Octobre 2007 en utilisant texi2html 1.78.