Emacs replace regexp with incremental sequence

Question

I am trying to figure out a way to replace a string in a text file by a number that increments by more than 1. I am trying to turn a couple of lines like this:

result_A_in_S1-S2.txt
result_A_in_S1-S2.txt
result_A_in_S1-S2.txt
result_A_in_S1-S2.txt

Into something that scales up sequentially for S1 and S2.

result_A_in_1000-1003.txt
result_A_in_1004-1007.txt
result_A_in_1008-1011.txt
result_A_in_1012-1015.txt

I want to know if I can define a string with replace regexp and then have that string be replaced with some starting number, and as it finds the next occurrence of string, it replaces with starting number + chosen increment.

I am just now starting learn Emacs and am pretty unfamiliar with it.

That was also my initial thought. I know there are other Q&As about generating sequences generally (which do tend to include answers like mine here, amongst other approaches), but this question had a specific need which seemed best met with a specific answer. — phils
– phils, Commented Mar 28, 2018 at 2:48

phils · Accepted Answer · 2018-03-27 20:34:38Z

6

Yes, you can do that with [query-]replace-regexp in Emacs, by evaluating elisp in your replacement, and utilising the zero-based replacement counter \#. e.g.:

M-x query-regexp-replace RET S1-S2 RET
\,(let ((start (+ 1000 (* 4 \#)))) (format "%d-%d" start (+ start 3))) RET

edited Mar 27, 2018 at 20:34

answered Mar 27, 2018 at 20:29

phils

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3 Comments

Cgeo629 Over a year ago

Thank you so very much, I found a much dumber brute force work around, but it this is lovely. I have still so much to learn about emacs.

Miserable Variable Over a year ago

@Cgeo629 it might have saved me some time today if you had explained your brute force workaround :) For my future reference, here's how I appended numbers with a computed value <kbd>M-x</kbd> query-regexp-replace <kbd>RET</kbd> .* <kbd>RET</kbd> \,(format "%s %d" \& (- (string-to-number \&) 616))` <kbd>RET</kbd> ` Can't get formatting to work in comments but I am sure I can figure it out next time

phils Over a year ago

FYI you can use \#& in place of (string-to-number \&) -- and likewise for backreferences \#1, \#2, etc, whenever capturing strings of numbers.

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