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The functions in this section rename, copy, delete, link, and set the modes (permissions) of files.
In the functions that have an argument newname, if a file by the name of newname already exists, the actions taken depend on the value of the argument ok-if-already-exists:
file-already-exists error if
ok-if-already-exists is nil.
The next four commands all recursively follow symbolic links at all
levels of parent directories for their first argument, but, if that
argument is itself a symbolic link, then only copy-file
replaces it with its (recursive) target.
This function gives the file named oldname the additional name newname. This means that newname becomes a new “hard link” to oldname.
In the first part of the following example, we list two files, foo and foo3.
$ ls -li fo* 81908 -rw-rw-rw- 1 rms rms 29 Aug 18 20:32 foo 84302 -rw-rw-rw- 1 rms rms 24 Aug 18 20:31 foo3
Now we create a hard link, by calling add-name-to-file, then list
the files again. This shows two names for one file, foo and
foo2.
(add-name-to-file "foo" "foo2")
⇒ nil
$ ls -li fo* 81908 -rw-rw-rw- 2 rms rms 29 Aug 18 20:32 foo 81908 -rw-rw-rw- 2 rms rms 29 Aug 18 20:32 foo2 84302 -rw-rw-rw- 1 rms rms 24 Aug 18 20:31 foo3
Finally, we evaluate the following:
(add-name-to-file "foo" "foo3" t)
and list the files again. Now there are three names for one file: foo, foo2, and foo3. The old contents of foo3 are lost.
(add-name-to-file "foo1" "foo3")
⇒ nil
$ ls -li fo* 81908 -rw-rw-rw- 3 rms rms 29 Aug 18 20:32 foo 81908 -rw-rw-rw- 3 rms rms 29 Aug 18 20:32 foo2 81908 -rw-rw-rw- 3 rms rms 29 Aug 18 20:32 foo3
This function is meaningless on operating systems where multiple names for one file are not allowed. Some systems implement multiple names by copying the file instead.
See also file-nlinks in File Attributes.
This command renames the file filename as newname.
If filename has additional names aside from filename, it
continues to have those names. In fact, adding the name newname
with add-name-to-file and then deleting filename has the
same effect as renaming, aside from momentary intermediate states.
This command copies the file oldname to newname. An error is signaled if oldname does not exist. If newname names a directory, it copies oldname into that directory, preserving its final name component.
If time is non-nil, then this function gives the new file
the same last-modified time that the old one has. (This works on only
some operating systems.) If setting the time gets an error,
copy-file signals a file-date-error error. In an
interactive call, a prefix argument specifies a non-nil value
for time.
If argument preserve-uid-gid is nil, we let the operating
system decide the user and group ownership of the new file (this is
usually set to the user running Emacs). If preserve-uid-gid is
non-nil, we attempt to copy the user and group ownership of the
file. This works only on some operating systems, and only if you have
the correct permissions to do so.
If the optional argument preserve-permissions is non-nil,
this function copies the file modes (or “permissions”) of
oldname to newname, as well as the Access Control List and
SELinux context (if any). See Information about Files.
Otherwise, the file modes of newname are left unchanged if it is
an existing file, and set to those of oldname, masked by the
default file permissions (see set-default-file-modes below), if
newname is to be newly created. The Access Control List or
SELinux context are not copied over in either case.
This command makes a symbolic link to filename, named newname. This is like the shell command ‘ln -s filename newname’.
This function is not available on systems that don’t support symbolic links.
This command deletes the file filename. If the file has
multiple names, it continues to exist under the other names. If
filename is a symbolic link, delete-file deletes only the
symbolic link and not its target (though it does follow symbolic links
at all levels of parent directories).
A suitable kind of file-error error is signaled if the file
does not exist, or is not deletable. (On Unix and GNU/Linux, a file
is deletable if its directory is writable.)
If the optional argument trash is non-nil and the
variable delete-by-moving-to-trash is non-nil, this
command moves the file into the system Trash instead of deleting it.
See Miscellaneous File Operations in The GNU
Emacs Manual. When called interactively, trash is t if
no prefix argument is given, and nil otherwise.
See also delete-directory in Create/Delete Dirs.
This function sets the file mode (or permissions) of filename to mode. It recursively follows symbolic links at all levels for filename.
If called non-interactively, mode must be an integer. Only the lowest 12 bits of the integer are used; on most systems, only the lowest 9 bits are meaningful. You can use the Lisp construct for octal numbers to enter mode. For example,
(set-file-modes #o644)
specifies that the file should be readable and writable for its owner,
readable for group members, and readable for all other users.
See File permissions in The GNU Coreutils
Manual, for a description of mode bit specifications.
Interactively, mode is read from the minibuffer using
read-file-modes (see below), which lets the user type in either
an integer or a string representing the permissions symbolically.
See File Attributes, for the function file-modes, which
returns the permissions of a file.
This function sets the default permissions for new files created by
Emacs and its subprocesses. Every file created with Emacs initially
has these permissions, or a subset of them (write-region will
not grant execute permissions even if the default file permissions
allow execution). On Unix and GNU/Linux, the default permissions are
given by the bitwise complement of the “umask” value.
The argument mode should be an integer which specifies the
permissions, similar to set-file-modes above. Only the lowest
9 bits are meaningful.
The default file permissions have no effect when you save a modified version of an existing file; saving a file preserves its existing permissions.
This function returns the default file permissions, as an integer.
This function reads a set of file mode bits from the minibuffer. The first optional argument prompt specifies a non-default prompt. Second second optional argument base-file is the name of a file on whose permissions to base the mode bits that this function returns, if what the user types specifies mode bits relative to permissions of an existing file.
If user input represents an octal number, this function returns that
number. If it is a complete symbolic specification of mode bits, as
in "u=rwx", the function converts it to the equivalent numeric
value using file-modes-symbolic-to-number and returns the
result. If the specification is relative, as in "o+g", then
the permissions on which the specification is based are taken from the
mode bits of base-file. If base-file is omitted or
nil, the function uses 0 as the base mode bits. The
complete and relative specifications can be combined, as in
"u+r,g+rx,o+r,g-w". See File permissions in The
GNU Coreutils Manual, for a description of file mode
specifications.
This function converts a symbolic file mode specification in
modes into the equivalent integer. If the symbolic
specification is based on an existing file, that file’s mode bits are
taken from the optional argument base-modes; if that argument is
omitted or nil, it defaults to 0, i.e., no access rights at
all.
This function sets the access and modification times of filename
to time. The return value is t if the times are successfully
set, otherwise it is nil. time defaults to the current
time and must be in the format returned by current-time
(see Time of Day).
This function sets the Emacs-recognized extended file attributes for
filename. The second argument attribute-alist should be
an alist of the same form returned by file-extended-attributes.
See Extended Attributes.
This function sets the SELinux security context for filename to
context. The context argument should be a list
(user role type range), where each
element is a string. See Extended Attributes.
The function returns t if it succeeds in setting the SELinux
context of filename. It returns nil if the context was
not set (e.g., if SELinux is disabled, or if Emacs was compiled
without SELinux support).
This function sets the Access Control List for filename to
acl. The acl argument should have the same form returned
by the function file-acl. See Extended Attributes.
The function returns t if it successfully sets the ACL of
filename, nil otherwise.
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