— Command: add-name-to-file oldname newname &optional ok-if-already-exists

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       29 Aug 18 20:32 foo
          84302 -rw-rw-rw-  1 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       29 Aug 18 20:32 foo
          81908 -rw-rw-rw-  2 rms       29 Aug 18 20:32 foo2
          84302 -rw-rw-rw-  1 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       29 Aug 18 20:32 foo
          81908 -rw-rw-rw-  3 rms       29 Aug 18 20:32 foo2
          81908 -rw-rw-rw-  3 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.

— Command: rename-file filename newname &optional ok-if-already-exists

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.

— Command: copy-file oldname newname &optional ok-if-exists time preserve-uid-gid

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.

This function copies the file modes, too.

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.

— Command: make-symbolic-link filename newname &optional ok-if-exists

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.

— Command: delete-file filename

This command deletes the file filename, like the shell command ‘rm filename’. If the file has multiple names, it continues to exist under the other names.

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 filename is a symbolic link, delete-file does not replace it with its target, but it does follow symbolic links at all levels of parent directories.

See also delete-directory in Create/Delete Dirs.

— Command: set-file-modes filename mode

This function sets mode bits of filename to mode (which must be an integer when the function is called non-interactively). Only the low 12 bits of mode are used.

Interactively, mode is read from the minibuffer using read-file-modes, which accepts mode bits either as a number or as a character string representing the mode bits symbolically. See the description of read-file-modes below for the supported forms of symbolic notation for mode bits.

This function recursively follows symbolic links at all levels for filename.

— Function: set-default-file-modes mode

This function sets the default file protection for new files created by Emacs and its subprocesses. Every file created with Emacs initially has this protection, or a subset of it (write-region will not give a file execute permission even if the default file protection allows execute permission). On Unix and GNU/Linux, the default protection is the bitwise complement of the “umask” value.

The argument mode must be an integer. On most systems, only the low 9 bits of mode are meaningful. You can use the Lisp construct for octal character codes to enter mode; for example,

          (set-default-file-modes ?\644)

Saving a modified version of an existing file does not count as creating the file; it preserves the existing file's mode, whatever that is. So the default file protection has no effect.

— Function: default-file-modes

This function returns the current default protection value.

— Function: read-file-modes &optional prompt base-file

This function reads file mode bits from the minibuffer. The optional argument prompt specifies a non-default prompt. 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, for detailed description of symbolic mode bits specifications.

— Function: file-modes-symbolic-to-number modes &optional base-modes

This subroutine converts a symbolic specification of file mode bits in modes into the equivalent numeric value. 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 zero, i.e. no access rights at all.

— Function: set-file-times filename &optional time

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).