M-x copyright is a skeleton inserting command, that adds a copyright notice at the point. The “by” part is taken from your environment variable $ORGANIZATION or if that isn't set you are prompted for it. If the buffer has a comment syntax (see Comments), this is inserted as a comment.
M-x copyright-update looks for a copyright notice in the first
copyright-limit characters of the buffer and updates it when necessary.
The current year (variable
copyright-current-year) is added to the
existing ones, in the same format as the preceding year, i.e., 1994, '94 or 94.
If a dash-separated year list up to last year is found, that is extended to
current year, else the year is added separated by a comma. Or it replaces
them when this is called with a prefix argument. If a header referring to a
wrong version of the GNU General Public License (see Copying) is found,
that is updated too.
An interesting application for this function is to have it be called
automatically every time a file is saved. This is accomplished by
(add-hook 'before-save-hook 'copyright-update) into
your ~/.emacs file (see Init File). Alternative,
you can do M-x customize-variable <RET> before-save-hook
copyright-update is conveniently listed as an
option in the customization buffer.
copyright-query controls whether to update the
copyright or whether to ask about it. When this is
nil updating is
only done with M-x copyright-update. When this is
you are queried whenever
copyright-update is called as a function,
such as in the
before-save-hook feature mentioned above. Otherwise
you are always queried.