How to search and replace carriage return with space

in Libre Office

Suppose you mean switching to new paragraph.
You can only replace all the paragraph shifts in a complete selection.
To do so

  • select the range
  • open ‘Find & Replace’
  • enter $ (nothing else) into ‘Search’
  • enter the replacement (in your case a space) into ‘Replace’
  • Check if options ‘Current selection only’ and ‘Regular expressions’ are checked
  • hitt ‘OK’

If your question was about hard line breaks: You find them with \n and you can combine this with other RegEx elements.

I am using ver. 5.2.7.2 and cannot make this work at all. In a file like this…

ANDERSON,
ANDREWS
ARMSTRONG
BALLANTINE
BARBOUR
BARBOURYOUNG
BRADLEY
BROWN
CAMPBELL
CARSON
CHADWICK
CHRISTIE
CLARKE
COCHRANE
COLEHAMILTON

I am trying to add a comma at the end of each line

Did you notice
0 - that this is a different question?
1 - that there isn’t a well defined thing like “end of the line” in word processors?
There are automatic line breaks, hard line breaks, and paragraph breaks.
2 - that you cannot replace automatic or hard linebreaks in the described way but only paragraph breaks?
3 - that you have to enter a comma (probably followed by a space) into ‘Replace’?