Search and replacement

Incremental search

C-s or M-x isearch-forward opens I-search: in the minibuffer. C-r or M-x isearch-backward opens I-search backward:. Type a literal query to find the first occurrence at or after point, or the last occurrence ending at or before point for backward search. Search does not wrap at either buffer edge.

Queries without uppercase characters use Unicode case-insensitive comparison. Any uppercase query character makes the entire query case-sensitive. Editing the query recalculates that choice immediately. Case-insensitive search uses Unicode 17.0.0 full default case folding, without locale-specific Turkic mappings or normalization. For example, strasse matches Straße, while STRASSE requires those exact capitals. Matches consume complete scalar expansions: ss can match ß, while s cannot match half of that expansion. Composed and decomposed accents stay distinct.

• Query edits update the result immediately. Prompt cursor movement, Home/End, Backspace/Delete and their Emacs equivalents edit only the query. Tab inserts a literal tab; bracketed paste can supply multiline Unicode or CRLF text.
• C-s continues after the current match; C-r continues before it. Switching direction finds the adjacent result in the newly chosen direction. Further query edits search from that continuation anchor. With no current match, a direction change uses the retained point. An empty query returns to the original starting point while retaining the chosen direction.
• A forward match moves point to its end; a backward match moves point to its start. Normal scrolling reveals that point in the selected pane. Underline identifies the match independently of the region's reverse video. Source matches may include part of a grapheme; cursor and highlighting cover whole graphemes, including CRLF pairs. Status, other panes and echo remain unstyled.
• No match appears beside the retained query when no result exists. Point stays at its last valid position, and removing query text can recover a match.
• Return accepts the current position and closes search. A fresh C-g cancels from any query, direction or failure state and restores the starting point, scrolling, intended column and recenter cycle in its original pane. Normal reveal then accommodates current terminal geometry. Neither action inserts query text, and a held Return cannot insert a second newline after acceptance.

Queries are limited to 4096 Unicode scalars. A rejected insertion preserves the existing query. Matching scans borrowed rope chunks and carries literal prefix state between them. Unicode folding expands each scalar to at most three scalars; matching keeps a bounded query/fallback table and a query-sized ring of original source positions. Backward search reverses its bounded query and traverses borrowed source characters backward across chunks. Neither direction creates a whole-buffer or folded-file copy on each query key.

Each result retains the original buffer identity, revision and half-open scalar range. If the live source changes, the stale result cannot be highlighted or restored; search closes with Search source changed. Search itself changes view and transient input state, leaving text, modification state and undo/redo transactions intact.

Query replace

M-% or M-x query-replace asks for Query replace: and then Replace with:. Return accepts each argument. The query must be nonempty; an empty replacement deletes accepted text. Both arguments support grapheme editing, literal Tab and bracketed multiline Unicode paste, bounded at 4096 scalars each. A replacement containing NUL is rejected. Query input and replacement drafts do not edit text.

Matching uses the same literal smart-case policy as incremental search, from the starting point to the active buffer's end, without wrapping. The selected pane reveals and underlines the current original source range. Replacement text is inserted exactly, with no case adjustment, backreferences or expression interpretation. A raw match may touch part of a grapheme; only its exact scalar range is replaced, while cursor and underline projection retain whole graphemes.

At Replace occurrence? [y/n/q], a fresh y replaces the displayed occurrence, n skips it and q stops. C-g stops at either argument or a decision. Return and other keys have no affirmative default. Paste and held/released answers cannot grant consent. Accepted replacements remain when the operation stops; undo reverses each accepted occurrence independently, leaving skipped text intact.

Continuation starts after the inserted text or skipped source range, so inserted query-looking text is not processed again. Empty replacements continue at the deletion boundary. Completion reports the accepted count; no matches reports zero without changing text, point or history. Read-only buffers refuse entry.

The operation retains its selected view, buffer, revision and current source range. A later source change invalidates its outstanding arguments/decision with Query replace source changed; a stale answer cannot edit another occurrence. Each accepted change uses the normal checked transaction, mapping shared views and marks and preserving literal LF/CRLF bytes. Normal editing remains available after completion, failure or cancellation, with no deferred replacement.