How to add a suffix to the end of a string in a line?

Question

Here's an example of content in a file

This_is_line_1    :  1
This_is_another_line  :2
This_is_3rd_line    :3
Here_is_line_4 :4

So, how can using emacs to add char @ immediately to the end 1 string on each line, i.e.

This_is_line_1@   :  1
This_is_another_line@  :2
This_is_3rd_line@    :3
Here_is_line_4@ :4

Don't forget to make @Tobias' answer as "The Answer". – RichieHH Feb 12 '20 at 18:50 — RichieHH, Feb 12 '20 at 18:50

Tobias · Accepted Answer · 2020-02-15T19:54:12.307

2

Go to the beginning of the buffer an call query-replace-regexp. You can call query-replace-regexp by the menu item "Edit → Replace → Replace Regexp". Alternatively you can use the key-sequence M-C-% that is shown beside the menu item.

Use ^[^[:space:]]+ as regular expression (regexp) and \&@ as replacement string.

Notes:

The first caret in the regexp matches the empty string at the beginnig of the line. It anchors the match at the beginning of the line.
The outer braces [...] describe a character set. Each of the contained characters match.
The caret in the character set negates the set. I.e., all characters not in the set do match.
The [:space:] is the character class of characters with space syntax.
The + matches one or more instances of the previous expression, i.e., of the character set.
The regexp is greedy by default. That means as many as possible chars are matched.
The \& in the replacement string references the full match.

edited Feb 15 '20 at 19:54

answered Feb 12 '20 at 07:54

Tobias

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Very informative. The docs are a little hard to follow. As a side note, the wonderful utility re-builder allows you to experiment! – RichieHH Feb 12 '20 at 18:58
@Tobias, thank you for your solution. – vbrnrt Feb 13 '20 at 17:14
I have a further question about the solution. If I want to put the 1st string between two '@' chars, what change do I need in step 7 of the provided solution. For instance, @This_is_another_line@ – vbrnrt Feb 13 '20 at 17:26
You get @This_is_another_line@ with @\&@. – Tobias Feb 13 '20 at 20:26
@Tobias, thank you for your following up solution. It works wonders. By the way, how/where can I find out the meaning of "&"? – vbrnrt Feb 15 '20 at 05:10
@vbrnrt I have added a link to the section Regexp Replace in the Emacs manual. – Tobias Feb 15 '20 at 19:55
@Tobias, thank you for the link. It's very helpful – vbrnrt Feb 17 '20 at 04:40

How to add a suffix to the end of a string in a line?

1 Answers1