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(elisp)Buffer File Name

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Enter node , (file) or (file)node

Buffer File Name
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   The "buffer file name" is the name of the file that is visited in
that buffer.  When a buffer is not visiting a file, its buffer file name
is `nil'.  Most of the time, the buffer name is the same as the
nondirectory part of the buffer file name, but the buffer file name and
the buffer name are distinct and can be set independently.  Note:
Visiting Files.

 - Function: buffer-file-name &optional buffer
     This function returns the absolute file name of the file that
     BUFFER is visiting.  If BUFFER is not visiting any file,
     `buffer-file-name' returns `nil'.  If BUFFER is not supplied, it
     defaults to the current buffer.

          (buffer-file-name (other-buffer))
               => "/usr/user/lewis/manual/files.texi"

 - Variable: buffer-file-name
     This buffer-local variable contains the name of the file being
     visited in the current buffer, or `nil' if it is not visiting a
     file.  It is a permanent local variable, unaffected by
     `kill-all-local-variables'.

          buffer-file-name
               => "/usr/user/lewis/manual/buffers.texi"

     It is risky to change this variable's value without doing various
     other things.  Normally it is better to use
     `set-visited-file-name' (see below); some of the things done
     there, such as changing the buffer name, are not strictly
     necessary, but others are essential to avoid confusing Emacs.

 - Variable: buffer-file-truename
     This buffer-local variable holds the truename of the file visited
     in the current buffer, or `nil' if no file is visited.  It is a
     permanent local, unaffected by `kill-all-local-variables'.  Note:
     Truenames.

 - Variable: buffer-file-number
     This buffer-local variable holds the file number and directory
     device number of the file visited in the current buffer, or `nil'
     if no file or a nonexistent file is visited.  It is a permanent
     local, unaffected by `kill-all-local-variables'.

     The value is normally a list of the form `(FILENUM DEVNUM)'.  This
     pair of numbers uniquely identifies the file among all files
     accessible on the system.  See the function `file-attributes', in
     Note: File Attributes, for more information about them.

 - Function: get-file-buffer filename
     This function returns the buffer visiting file FILENAME.  If there
     is no such buffer, it returns `nil'.  The argument FILENAME, which
     must be a string, is expanded (Note: File Name Expansion), then
     compared against the visited file names of all live buffers.

          (get-file-buffer "buffers.texi")
              => #<buffer buffers.texi>

     In unusual circumstances, there can be more than one buffer
     visiting the same file name.  In such cases, this function returns
     the first such buffer in the buffer list.

 - Command: set-visited-file-name filename &optional no-query
          along-with-file
     If FILENAME is a non-empty string, this function changes the name
     of the file visited in the current buffer to FILENAME.  (If the
     buffer had no visited file, this gives it one.)  The _next time_
     the buffer is saved it will go in the newly-specified file.  This
     command marks the buffer as modified, since it does not (as far as
     Emacs knows) match the contents of FILENAME, even if it matched the
     former visited file.

     If FILENAME is `nil' or the empty string, that stands for "no
     visited file".  In this case, `set-visited-file-name' marks the
     buffer as having no visited file.

     Normally, this function asks the user for confirmation if the
     specified file already exists.  If NO-QUERY is non-`nil', that
     prevents asking this question.

     If ALONG-WITH-FILE is non-`nil', that means to assume that the
     former visited file has been renamed to FILENAME.

     When the function `set-visited-file-name' is called interactively,
     it prompts for FILENAME in the minibuffer.

 - Variable: list-buffers-directory
     This buffer-local variable specifies a string to display in a
     buffer listing where the visited file name would go, for buffers
     that don't have a visited file name.  Dired buffers use this
     variable.