@menu
* File Name Components:: The directory part of a file name, and the rest.
+* Relative File Names:: Some file names are relative to a current directory.
* Directory Names:: A directory's name as a directory
is different from its name as a file.
-* Relative File Names:: Some file names are relative to a current directory.
* File Name Expansion:: Converting relative file names to absolute ones.
* Unique File Names:: Generating names for temporary files.
* File Name Completion:: Finding the completions for a given file name.
found mostly in directory lists.
@defun file-name-directory filename
-This function returns the directory part of @var{filename} (or
-@code{nil} if @var{filename} does not include a directory part). On
-most systems, the function returns a string ending in a slash. On VMS,
-it returns a string ending in one of the three characters @samp{:},
+This function returns the directory part of @var{filename}, as a
+directory name (@pxref{Directory Names}), or @code{nil} if
+@var{filename} does not include a directory part.
+
+On GNU and Unix systems, a string returned by this function always
+ends in a slash. On MSDOS it can also end in a colon. On VMS, it
+returns a string ending in one of the three characters @samp{:},
@samp{]}, or @samp{>}.
@example
@result{} "foo"
@end group
@group
+(file-name-nondirectory "lewis/")
+ @result{} ""
+@end group
+@group
;; @r{The following example is accurate only on VMS.}
(file-name-nondirectory "[X]FOO.TMP")
@result{} "FOO.TMP"
@end example
@end defun
+@defun file-name-extension filename &optional period
+This function returns @var{filename}'s final ``extension,'' if any,
+after applying @code{file-name-sans-versions} to remove any
+version/backup part. It returns @code{nil} for extensionless file
+names such as @file{foo}. If @var{period} is non-nil, then the
+returned value includes the period that delimits the extension, and if
+@var{filename} has no extension, the value is @code{""}. If the last
+component of a file name begins with a @samp{.}, that @samp{.} doesn't
+count as the beginning of an extension, so, for example,
+@file{.emacs}'s ``extension'' is @code{nil}, not @samp{.emacs}.
+@end defun
+
@defun file-name-sans-versions filename &optional keep-backup-version
This function returns @var{filename} with any file version numbers,
backup version numbers, or trailing tildes discarded.
@end defvar
@end ignore
-@defun file-name-extension filename &optional period
-This function returns @var{filename}'s final ``extension,'' if any,
-after applying @code{file-name-sans-versions} to remove any
-version/backup part. It returns @code{nil} for extensionless file
-names such as @file{foo}. If @var{period} is non-nil, then the
-returned value includes the period that delimits the extension, and if
-@var{filename} has no extension, the value is @code{""}. If the last
-component of a file name begins with a @samp{.}, that @samp{.} doesn't
-count as the beginning of an extension, so, for example,
-@file{.emacs}'s ``extension'' is @code{nil}, not @samp{.emacs}.
+@node Relative File Names
+@subsection Absolute and Relative File Names
+@cindex absolute file name
+@cindex relative file name
+
+ All the directories in the file system form a tree starting at the
+root directory. A file name can specify all the directory names
+starting from the root of the tree; then it is called an @dfn{absolute}
+file name. Or it can specify the position of the file in the tree
+relative to a default directory; then it is called a @dfn{relative} file
+name. On Unix and GNU/Linux, an absolute file name starts with a slash
+or a tilde (@samp{~}), and a relative one does not. On MS-DOS and
+MS-Windows, an absolute file name starts with a slash or a backslash, or
+with a drive specification @samp{@var{x}:/}, where @var{x} is the
+@dfn{drive letter}. The rules on VMS are complicated.
+
+@defun file-name-absolute-p filename
+This function returns @code{t} if file @var{filename} is an absolute
+file name, @code{nil} otherwise. On VMS, this function understands both
+Unix syntax and VMS syntax.
+
+@example
+@group
+(file-name-absolute-p "~rms/foo")
+ @result{} t
+@end group
+@group
+(file-name-absolute-p "rms/foo")
+ @result{} nil
+@end group
+@group
+(file-name-absolute-p "/user/rms/foo")
+ @result{} t
+@end group
+@end example
@end defun
@node Directory Names
@cindex directory name
@cindex file name of directory
- A @dfn{directory name} is the name of a directory. A directory is a
-kind of file, and it has a file name, which is related to the directory
-name but not identical to it. (This is not quite the same as the usual
-Unix terminology.) These two different names for the same entity are
-related by a syntactic transformation. On most systems, this is simple:
-a directory name ends in a slash (or backslash), whereas the directory's
-name as a file lacks that slash. On VMS, the relationship is more
-complicated.
+ A @dfn{directory name} is the name of a directory. A directory is
+actually a kind of file, so it has a file name, which is related to
+the directory name but not identical to it. (This is not quite the
+same as the usual Unix terminology.) These two different names for
+the same entity are related by a syntactic transformation. On GNU and
+Unix systems, this is simple: a directory name ends in a slash (or
+backslash), whereas the directory's name as a file lacks that slash.
+On MSDOS and VMS, the relationship is more complicated.
The difference between a directory name and its name as a file is
subtle but crucial. When an Emacs variable or function argument is
described as being a directory name, a file name of a directory is not
-acceptable.
+acceptable. When @code{file-name-directory} returns a string, that is
+always a directory name.
The following two functions convert between directory names and file
names. They do nothing special with environment variable substitutions
@end example
@end defun
+ Given a directory name, you can combine it with a relative file name
+using @code{concat}:
+
+@example
+(concat @var{dirname} @var{relfile})
+@end example
+
+@noindent
+Be sure to verify that the file name is relative before doing that.
+If you use an absolute file name, the results could be syntactically
+invalid or refer to the wrong file.
+
+ If you want to use a directory file name in making such a
+combination, you must first convert it to a directory name using
+@code{file-name-as-directory}:
+
+@example
+(concat (file-name-as-directory @var{dirfile}) @var{relfile})
+@end example
+
+@noindent
+Don't try concatenating a slash by hand, as in
+
+@example
+;;; @r{Wrong!}
+(concat @var{dirfile} "/" @var{relfile})
+@end example
+
+@noindent
+because this is not portable. Always use
+@code{file-name-as-directory}.
+
@cindex directory name abbreviation
Directory name abbreviations are useful for directories that are
normally accessed through symbolic links. Sometimes the users recognize
To convert a directory name to its abbreviation, use this
function:
-@defun abbreviate-file-name dirname
+@defun abbreviate-file-name filename
This function applies abbreviations from @code{directory-abbrev-alist}
to its argument, and substitutes @samp{~} for the user's home
-directory.
-@end defun
-
-@node Relative File Names
-@subsection Absolute and Relative File Names
-@cindex absolute file name
-@cindex relative file name
-
- All the directories in the file system form a tree starting at the
-root directory. A file name can specify all the directory names
-starting from the root of the tree; then it is called an @dfn{absolute}
-file name. Or it can specify the position of the file in the tree
-relative to a default directory; then it is called a @dfn{relative} file
-name. On Unix and GNU/Linux, an absolute file name starts with a slash
-or a tilde (@samp{~}), and a relative one does not. On MS-DOS and
-MS-Windows, an absolute file name starts with a slash or a backslash, or
-with a drive specification @samp{@var{x}:/}, where @var{x} is the
-@dfn{drive letter}. The rules on VMS are complicated.
-
-@defun file-name-absolute-p filename
-This function returns @code{t} if file @var{filename} is an absolute
-file name, @code{nil} otherwise. On VMS, this function understands both
-Unix syntax and VMS syntax.
-
-@example
-@group
-(file-name-absolute-p "~rms/foo")
- @result{} t
-@end group
-@group
-(file-name-absolute-p "rms/foo")
- @result{} nil
-@end group
-@group
-(file-name-absolute-p "/user/rms/foo")
- @result{} t
-@end group
-@end example
+directory. You can use it for directory names and for file names,
+because it recognizes abbreviations even as part of the name.
@end defun
@node File Name Expansion
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