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Asked: 2026-05-25T18:14:47+00:00

I am trying to write a regular expression in vi to match any whitespace

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I am trying to write a regular expression in vi to match any whitespace character followed by any digit. Then, at each match, insert a dollar sign between the whitespace and the digit. Here is an example:

A1234 12 14 B1234
B1256 A2 14 C1245
C1234 34 D1 1234K

The correct regex would produce this:

A1234 $12 $14 B1234
B1256 A2 14 C1245
C1234 $34 D1 $1234K

I realize I need to use a back reference, but I can’t quite seem to write the correct regex. Here is my attempt:

:'<,'>/(\s\d)/\s\1\$/g

Also, I have Vim’s default regex mode turned off (vnoremap / /\v).

Thanks for the help.

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1 Answer

  1. Editorial Team

    You need to escape the parentheses to make them work as groupings rather than as actual matches in the text, and not escape the $. Like so:

    :%s/\(\s\)\(\d\)/\1$\2/g

    This worked for me in vim (using standard magic setting).

    Edit: just realized that your non-standard regex settings cause you having the escape ‘the other way around’. But still, the trick, I think, is to use two groups. With your settings, this should work:

    :%s/(\s)(\d)/\1$\2/g
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