GNU Info

(librep.info)File Names

---

Next: File Objects Up: Files

---

Enter node , (file) or (file)node

File Names
----------

   A "file name" is a string identifying an individual file (or
directory) in the filing system (i.e. the disk). The exact syntax of
file names depends on the operating system. There are several functions
for manipulating file names.

 - Function: file-name-absolute-p file-name
     Returns true when FILE-NAME is not specified relative to the
     current directory.

 - Function: file-name-directory file-name
     This function returns the directory part of the file name string
     FILE-NAME. This is the substring of FILE-NAME defining the
     directory containing the file.

          (file-name-directory "/tmp/foo")
              => "/tmp/"
          
          (file-name-directory "foo")
              => ""
          
          (file-name-directory "foo/bar/")
              => "foo/bar/"

 - Function: file-name-nondirectory file-name
     Returns the substring of the file name FILE-NAME which is _not_
     the directory part.

          (file-name-nondirectory "/tmp/foo")
              => "foo"
          
          (file-name-nondirectory "foo")
              => "foo"
          
          (file-name-nondirectory "foo/bar/")
              => ""

 - Function: file-name-as-directory file-name
     Returns a string through which the item in the file system named by
     FILE-NAME can be referred to as a directory.

          (file-name-as-directory "./foo")
              => "./foo/"
          
          (file-name-as-directory "./foo/")
              => "./foo/"

 - Function: directory-file-name directory-name
     Returns a string through which the directory named by
     DIRECTORY-NAME can be referred to as a file.

          (directory-file-name "./foo/")
              => "./foo"
          
          (directory-file-name "./foo")
              => "./foo"

 - Function: expand-file-name file-name #!optional base-dir
     Expands FILE-NAME assuming that it specifies a file relative to
     BASE-DIR. If BASE-DIR is undefined it is taken as the current
     value of the `default-directory' variable. While expanding the
     file name, any obvious simplifications will be performed (e.g. on
     Unix the removal of "." and ".." where possible).

     Note that the returned file name will only be absolute if one of
     the following conditions is met:

       1. BASE-DIR (or `default-directory') is absolute,

       2. FILE-NAME is already absolute.

          (expand-file-name "foo" "./bar")
              => "bar/foo"

     Note for file handler implementors: when a handler is called for
     the `expand-file-name' operation, it will only ever receive one
     argument, the already expanded file name. The only action that may
     be need to be taken is to simplify the file name (e.g. removing `.'
     and `..' entries or whatever).

 - Function: canonical-file-name file-name
     This function returns the canonical name of the file referred to
     by the string FILE-NAME. The canonical name of a file is defined
     such that two files can be compared simply by comparing their
     canonical names; if the names match, they refer to the same file.

     (Note that the opposite isn't always true, if two canonical names
     don't match the files could still be the same, for example via
     hard links. On most operating systems, symbolic links will be
     expanded where possible.

          (canonical-file-name "foo")
              => "/home/john/src/librep/man/foo"

 - Function: local-file-name file-name
     `librep' supports extensible file handling (Note: File
     Handlers), so file names may refer to files not residing in the
     system's local file structure, and thus which are unavailable to
     other programs.

     This function returns either the absolute name of the file
     FILE-NAME, if it is found in the local system, or false, if the
     file does not.

          (local-file-name "foo")
              => "/home/john/src/librep/man/foo"
          
          (local-file-name "/john@tango:foo")
              => ()

 - Function: make-temp-name
     This function returns the name of a file which, when created, may
     be used for temporary storage. Each time this function is called a
     unique name is computed.

          (make-temp-name)
              => "/tmp/00088aaa"
          
          (make-temp-name)
              => "/tmp/00088baa"

 - Variable: default-directory
     This variable names the current working directory. All relative
     file names are interpreted starting from this location in the file
     system.