8.4 Minibuffer History

Every argument that you enter with the minibuffer is saved in a minibuffer history list so you can easily use it again later. You can use the following arguments to quickly fetch an earlier argument into the minibuffer:

M-p

<Up>

Move to the previous item in the minibuffer history, an earlier argument (previous-history-element).

M-n

<Down>

Move to the next item in the minibuffer history (next-history-element).

M-r regexp <RET>

Move to an earlier item in the minibuffer history that matches regexp (previous-matching-history-element).

M-s regexp <RET>

Move to a later item in the minibuffer history that matches regexp (next-matching-history-element).

While in the minibuffer, typing M-p or <Up> (previous-history-element) moves up through the minibuffer history list, one item at a time. Each M-p fetches an earlier item from the history list into the minibuffer, replacing its existing contents. Similarly, typing M-n or <Down> (next-history-element) moves back down the history list, fetching later entries into the minibuffer. You can think of these commands as “backwards” and “forwards” through the history list.

If you type M-n in the minibuffer when there are no later entries in the minibuffer history (⁖, if you haven't previously typed M-p), Emacs tries fetching from a list of default argument: values that you are likely to enter. You can think of this as moving through the “future list” instead of the “history list”.

The input that M-p or M-n fetches into the minibuffer entirely replaces the existing contents of the minibuffer, so you can simply type <RET> to use it as an argument. You can also edit the text before you reuse it; this does not change the history element that you “moved” to, but your new argument does go at the end of the history list in its own right.

There are also commands to search forward or backward through the history; they search for history elements that match a regular expression. M-r (previous-matching-history-element) searches older elements in the history, while M-s (next-matching-history-element) searches newer elements. These commands are unusual: they use the minibuffer to read the regular expression even though they are invoked from the minibuffer. As with incremental searching, an upper-case letter in the regular expression makes the search case-sensitive (see Search Case). You can also search through the history using an incremental search (see Isearch Minibuffer).

All uses of the minibuffer record your input on a history list, but there are separate history lists for different kinds of arguments. For example, there is a list for file names, used by all the commands that read file names. (As a special feature, this history list records the absolute file name, even if the name you entered was not absolute.)

There are several other specific history lists, including one for buffer names, one for arguments of commands like query-replace, one used by M-x for command names, and one used by compile for compilation commands. Finally, there is one “miscellaneous” history list that most minibuffer arguments use.

The variable history-length specifies the maximum length of a minibuffer history list; adding a new element deletes the oldest element if the list gets too long. If the value of history-length is t, there is no maximum length.

The variable history-delete-duplicates specifies whether to delete duplicates in history. If it is non-nil, adding a new element deletes from the list all other elements that are equal to it. The default is nil.