This section describes the functions for getting detailed information about a file, including the owner and group numbers, the number of names, the inode number, the size, and the times of access and modification.
This function returns t if the file filename1 is
newer than file filename2. If filename1 does not
exist, it returns nil. If filename1 does exist, but
filename2 does not, it returns t.
In the following example, assume that the file aug-19 was written on the 19th, aug-20 was written on the 20th, and the file no-file doesn’t exist at all.
(file-newer-than-file-p "aug-19" "aug-20")
⇒ nil
(file-newer-than-file-p "aug-20" "aug-19")
⇒ t
(file-newer-than-file-p "aug-19" "no-file")
⇒ t
(file-newer-than-file-p "no-file" "aug-19")
⇒ nil
This function returns non-nil if the time stamp of
filename has changed since the last call. When called for the
first time for some filename, it records the last modification
time and size of the file, and returns non-nil when
filename exists. Thereafter, when called for the same
filename, it compares the current time stamp and size with the
recorded ones, and returns non-nil only if either the time
stamp or the size (or both) are different. This is useful when a Lisp
program wants to re-read a file whenever it changes. With an optional
argument tag, which must be a symbol, the size and modification
time comparisons are limited to calls with the same tag.
This function returns a list of attributes of file filename. If
the specified file does not exist, it returns nil.
This function does not follow symbolic links.
The optional parameter id-format specifies the preferred format
of attributes UID and GID (see below)—the
valid values are 'string and 'integer. The latter is
the default, but we plan to change that, so you should specify a
non-nil value for id-format if you use the returned
UID or GID.
On GNU platforms when operating on a local file, this function is
atomic: if the filesystem is simultaneously being changed by some
other process, this function returns the file’s attributes either
before or after the change. Otherwise this function is not atomic,
and might return nil if it detects the race condition, or might
return a hodgepodge of the previous and current file attributes.
Accessor functions are provided to access the elements in this list. The accessors are mentioned along with the descriptions of the elements below.
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
(file-attribute-type).
file-attribute-link-number).
Alternate names, also known as hard links, can be created by using the
add-name-to-file function (see Changing File Names and Attributes).
file-attribute-user-id). However, if it does not correspond
to a named user, the value is an integer.
file-attribute-group-id).
file-attribute-access-time). The timestamp is in the
style of current-time (see Time of Day) and is truncated
to that of the filesystem’s timestamp resolution; for example, on some
FAT-based filesystems, only the date of last access is recorded, so
this time will always hold the midnight of the day of the last access.
file-attribute-modification-time). This is the last time when
the file’s contents were modified.
file-attribute-status-change-time). This is the time of the
last change to the file’s access mode bits, its owner and group, and
other information recorded in the filesystem for the file, beyond the
file’s contents.
file-attribute-size).
file-attribute-modes).
file-attribute-inode-number),
a nonnegative integer.
file-attribute-device-number), an integer or a cons cell of
two integers. The latter is sometimes used by remote files, in order
to distinguish remote filesystems from local ones.
The file’s inode and device together give enough information
to distinguish any two files on the system—no two files can have the
same values for both of these attributes. This tuple that uniquely
identifies the file is returned by file-attribute-file-identifier.
For example, here are the file attributes for files.texi:
(file-attributes "files.texi" 'string)
⇒ (nil 1 "lh" "users"
(20614 64019 50040 152000)
(20000 23 0 0)
(20614 64555 902289 872000)
122295 "-rw-rw-rw-"
t 6473924464520138
1014478468)
and here is how the result is interpreted:
nilis neither a directory nor a symbolic link.
1has only one name (the name files.texi in the current default directory).
"lh"is owned by the user with name ‘lh’.
"users"is in the group with name ‘users’.
(20614 64019 50040 152000)was last accessed on October 23, 2012, at 20:12:03.050040152 UTC.
(This timestamp is (1351023123050040152 . 1000000000)
if current-time-list is nil.)
(20000 23 0 0)was last modified on July 15, 2001, at 08:53:43.000000000 UTC.
(This timestamp is (1310720023000000000 . 1000000000)
if current-time-list is nil.)
(20614 64555 902289 872000)last had its status changed on October 23, 2012, at 20:20:59.902289872 UTC.
(This timestamp is (1351023659902289872 . 1000000000)
if current-time-list is nil.)
122295is 122295 bytes long. (It may not contain 122295 characters, though, if some of the bytes belong to multibyte sequences, and also if the end-of-line format is CR-LF.)
"-rw-rw-rw-"has a mode of read and write access for the owner, group, and world.
tis merely a placeholder; it carries no information.
6473924464520138has an inode number of 6473924464520138.
1014478468is on the file-system device whose number is 1014478468.
This function returns the number of names (i.e., hard links) that
file filename has. If the file does not exist, 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. This function does not follow symbolic links.
$ ls -l foo* -rw-rw-rw- 2 rms rms 4 Aug 19 01:27 foo -rw-rw-rw- 2 rms rms 4 Aug 19 01:27 foo1
(file-nlinks "foo")
⇒ 2
(file-nlinks "doesnt-exist")
⇒ nil