GNU Info

(elisp)File Attributes

---

Prev: Truenames Up: Information about Files

---

Enter node , (file) or (file)node

Other Information about Files
-----------------------------

   This section describes the functions for getting detailed information
about a file, other than its contents.  This information includes the
mode bits that control access permission, the owner and group numbers,
the number of names, the inode number, the size, and the times of access
and modification.

 - Function: file-modes filename
     This function returns the mode bits of FILENAME, as an integer.
     The mode bits are also called the file permissions, and they
     specify access control in the usual Unix fashion.  If the
     low-order bit is 1, then the file is executable by all users, if
     the second-lowest-order bit is 1, then the file is writable by all
     users, etc.

     The highest value returnable is 4095 (7777 octal), meaning that
     everyone has read, write, and execute permission, that the SUID bit
     is set for both others and group, and that the sticky bit is set.

          (file-modes "~/junk/diffs")
               => 492               ; Decimal integer.
          (format "%o" 492)
               => "754"             ; Convert to octal.
          
          (set-file-modes "~/junk/diffs" 438)
               => nil
          
          (format "%o" 438)
               => "666"             ; Convert to octal.
          
          % ls -l diffs
            -rw-rw-rw-  1 lewis 0 3063 Oct 30 16:00 diffs

 - Function: file-nlinks filename
     This functions returns the number of names (i.e., hard links) that
     file FILENAME has.  If the file does not exist, then this function
     returns `nil'.  Note that symbolic links have no effect on this
     function, because they are not considered to be names of the files
     they link to.

          % ls -l foo*
          -rw-rw-rw-  2 rms       4 Aug 19 01:27 foo
          -rw-rw-rw-  2 rms       4 Aug 19 01:27 foo1
          
          (file-nlinks "foo")
               => 2
          (file-nlinks "doesnt-exist")
               => nil

 - Function: file-attributes filename
     This function returns a list of attributes of file FILENAME.  If
     the specified file cannot be opened, it returns `nil'.

     The elements of the list, in order, are:

       0. `t' for a directory, a string for a symbolic link (the name
          linked to), or `nil' for a text file.

       1. The number of names the file has.  Alternate names, also
          known as hard links, can be created by using the
          `add-name-to-file' function (Note: Changing Files).

       2. The file's UID.

       3. The file's GID.

       4. The time of last access, as a list of two integers.  The
          first integer has the high-order 16 bits of time, the second
          has the low 16 bits.  (This is similar to the value of
          `current-time'; see Note: Time of Day.)

       5. The time of last modification as a list of two integers (as
          above).

       6. The time of last status change as a list of two integers (as
          above).

       7. The size of the file in bytes.  If the size is too large to
          fit in a Lisp integer, this is a floating point number.

       8. The file's modes, as a string of ten letters or dashes, as in
          `ls -l'.

       9. `t' if the file's GID would change if file were deleted and
          recreated; `nil' otherwise.

      10. The file's inode number.  If possible, this is an integer.
          If the inode number is too large to be represented as an
          integer in Emacs Lisp, then the value has the form `(HIGH .
          LOW)', where LOW holds the low 16 bits.

      11. The file system number of the file system that the file is in.
          Depending on the magnitude of the value, this can be either
          an integer or a cons cell, in the same manner as the inode
          number.  This element and the file's inode number together
          give enough information to distinguish any two files on the
          system--no two files can have the same values for both of
          these numbers.

     For example, here are the file attributes for `files.texi':

          (file-attributes "files.texi")
               =>  (nil 1 2235 75
                    (8489 20284)
                    (8489 20284)
                    (8489 20285)
                    14906 "-rw-rw-rw-"
                    nil 129500 -32252)

     and here is how the result is interpreted:

    `nil'
          is neither a directory nor a symbolic link.

    `1'
          has only one name (the name `files.texi' in the current
          default directory).

    `2235'
          is owned by the user with UID 2235.

    `75'
          is in the group with GID 75.

    `(8489 20284)'
          was last accessed on Aug 19 00:09.

    `(8489 20284)'
          was last modified on Aug 19 00:09.

    `(8489 20285)'
          last had its inode changed on Aug 19 00:09.

    `14906'
          is 14906 bytes long.  (It may not contain 14906 characters,
          though, if some of the bytes belong to multibyte sequences.)

    `"-rw-rw-rw-"'
          has a mode of read and write access for the owner, group, and
          world.

    `nil'
          would retain the same GID if it were recreated.

    `129500'
          has an inode number of 129500.

    `-32252'
          is on file system number -32252.