Preset search isearch-string from command line

Question

I am trying to set isearch-string from the command line. The purpose is to have a Perl script start Emacs with a given search string, and go directly to the first line of the string and enter search mode. For example:

$ emacs +2 t.txt -l srep.el &

with t.txt the text file to search in, for example here is a dummy file:

a bb c
aa
aa bb c d

The Lisp file srep.el (generated by the Perl script) sets the isearch-string, for example:

(setq isearch-string "aa")
(isearch-search-and-update)

However, this does not work. I get a wrong-type-argument error from the debugger. I then modified srep.el to :

(defun my-set-search-word()
  (interactive)
  (setq isearch-string "aa"))

(add-hook 'isearch-mode-hook 'my-set-search-word)

This works in the beginning. I can press C-s to search for the string aa, but if I try to escape isearch-mode (press arrow up key for example) and do some editing and later try to search for another string (by pressing C-s again) for example the string b. I get error Failing I-search.

I tried to solve this by changing srep.el to:

(defun my-set-search-word()
  (interactive)
  (if *my-search-str-flag*
      (setq isearch-string "aa")
    (setq *my-search-str-flag* nil)))

(defun my-set-search-word()
  (interactive)
  (setq isearch-string "aa"))

(defvar *my-search-str-flag* t)
(add-hook 'isearch-mode-hook 'my-set-search-word)

But I still get same behavior. I am using Emacs 24.3 on Ubuntu 14.04.

Answer 1

What I recommend you to try is to start Isearch first and then yank your word to the search string, effectively doing the same what you would do manually to add words in isearch-mode:

(defun my-search-word ()
  (interactive)
  (isearch-forward nil 1)
  (isearch-yank-string "aa"))

(my-search-word)

If you need to match word boundaries, then try this:

(defun my-search-word ()
  (interactive)
  (isearch-forward-word nil 1)
  (isearch-yank-string "aa"))

(my-search-word)