Bookmarks are somewhat like registers in that they record positions you can jump to. Unlike registers, they have long names, and they persist automatically from one Emacs session to the next. The prototypical use of bookmarks is to record where you were reading in various files.
The prototypical use for bookmarks is to record one current position in each of several files. So the command C-x r m, which sets a bookmark, uses the visited file name as the default for the bookmark name. If you name each bookmark after the file it points to, then you can conveniently revisit any of those files with C-x r b, and move to the position of the bookmark at the same time.
The command C-x r M (
like C-x r m, but it signals an error if the specified bookmark
already exists, instead of overwriting it.
To display a list of all your bookmarks in a separate buffer, type
C-x r l (
list-bookmarks). If you switch to that buffer,
you can use it to edit your bookmark definitions or annotate the
bookmarks. Type C-h m in the bookmark buffer for more
information about its special editing commands.
When you kill Emacs, Emacs saves your bookmarks, if you have changed any bookmark values. You can also save the bookmarks at any time with the M-x bookmark-save command. Bookmarks are saved to the file ~/.emacs.d/bookmarks (for compatibility with older versions of Emacs, if you have a file named ~/.emacs.bmk, that is used instead). The bookmark commands load your default bookmark file automatically. This saving and loading is how bookmarks persist from one Emacs session to the next.
If you set the variable
bookmark-save-flag to 1, each command
that sets a bookmark will also save your bookmarks; this way, you
don't lose any bookmark values even if Emacs crashes. The value, if
a number, says how many bookmark modifications should go by between
saving. If you set this variable to
nil, Emacs only
saves bookmarks if you explicitly use M-x bookmark-save.
bookmark-default-file specifies the file in
which to save bookmarks by default.
Bookmark position values are saved with surrounding context, so that
bookmark-jump can find the proper position even if the file is
modified slightly. The variable
bookmark-search-size says how
many characters of context to record on each side of the bookmark's
Here are some additional commands for working with bookmarks:
bookmark-write, to work with other files of bookmark values in addition to your default bookmark file.