25.6.4 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:
-
t
for a directory, a string for a symbolic link (the name
linked to), or nil
for a text file.
-
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
(see section 25.7 Changing File Names and Attributes).
-
The file's UID.
-
The file's GID.
-
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 40.5 Time of Day.)
-
The time of last modification as a list of two integers (as above).
-
The time of last status change as a list of two integers (as above).
-
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.
-
The file's modes, as a string of ten letters or dashes,
as in `ls -l'.
-
t
if the file's GID would change if file were
deleted and recreated; nil
otherwise.
-
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.
-
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.
This document was generated
on May 2, 2002
using texi2html