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#### 24.6.3 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

  This function returns the truename of the file filename. If the argument is not an absolute file name, this function first expands it against `default-directory`.

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

  If you may need to follow symbolic links preceding ‘`..`’ appearing as a name component, call `file-truename` without prior direct or indirect calls to `expand-file-name`. 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. See 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"

Function: file-equal-p file1 file2

  This function returns `t` if the files file1 and file2 name the same file. This is similar to comparing their truenames, except that remote file names are also handled in an appropriate manner. If file1 or file2 does not exist, the return value is unspecified.

Function: file-in-directory-p file dir

  This function returns `t` if file is a file in directory dir, or in a subdirectory of dir. It also returns `t` if file and dir are the same directory. It compares the truenames of the two directories. If dir does not name an existing directory, the return value is `nil`.

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