How to make C-s (isearch-forward) and C-r (isearch-backward) search only for words that start with the argument passed to them, instead of searching for the argument even if it's in the middle of a word?
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1For 2) see section "Position of the Cursor after Searching" here emacswiki.org/emacs/IncrementalSearch– andrejCommented Nov 29, 2018 at 10:38
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Please post two separate questions for your two separate question. As it stands now, the question is too broad and may be deleted.– DrewCommented Nov 29, 2018 at 18:06
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3 Answers
You can either toggle word-search-mode by doing M-s w after starting isearch, or you can use start in word search mode directly using isearch-forward-word, also bound to M-s w.
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I tried it first, but unfortunately, it doesn't seem to have an equivalent
isearch-backward-word. And it only shows the first matched word, with no way (apparently) to go to the next match. Commented Nov 29, 2018 at 16:08 -
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isearch-backward-worddoesn't exist, but you can doC-r M-s w, or write it and choose your own binding. Once you're in word mode you can just useC-sorC-rto go to the next match.– rpluimCommented Nov 29, 2018 at 16:28
word-search-mode is the usual way to constrain your searches to words rather than letters, as @rpluim shows.
An alternative, more general approach is to use regular expression searches, isearch-forward-regexp, or C-M-s, and also the reverse isearch-backward-regexp and C-M-r. You can then use a regular expression to limit your search: \bin will match in when it occurs at the start of a word.
This is not as convenient as word-search-mode, but it is more flexible. For instance, you could find words ending with er with er\b.
Here's what I use to do this
;; Use isearch-forward-word by default (treats a space as any whitespace or punctuation)
(global-set-key (kbd "C-s") 'isearch-forward-word)
;; This is the same as isearch-forward-word except with the first argument to
;; isesarch-mode set to nil to do reverse search
(defun isearch-backward-word (&optional not-word no-recursive-edit)
"Do incremental search backward for a sequence of words.
With a prefix argument, do a regular string search instead.
Like ordinary incremental search except that your input is treated
as a sequence of words without regard to how the words are separated.
See the command `isearch-forward' for more information.
This command does not support character folding, and lax space matching
has no effect on it."
(interactive "P\np")
(isearch-mode nil nil nil (not no-recursive-edit) (null not-word)))
(global-set-key (kbd "C-r") 'isearch-backward-word)
isearch-backward-word doesn't exist so I just copied the source of isearch-forward-word and changed the first argument of isearch-mode to nil to do reverse isearch.
