Question

If I have a file:

aaa / new replacement line
AAA / old target line
random line
random line 
BBB / old target line
CCC / old target line

In this example there are 4 replacements, so the final file should end up like:

aaa / new replacement line
aaa / new replacement line
random line
random line 
aaa / new replacement line
aaa / new replacement line

I have an attempt at an answer below but would like to see your input on this also.
Maybe there is a more successful ‘vim golf’ approach I am unaware of. Maybe I’m just being really dumb and there is a simple command for this.

Basically, the question is this: if I have a line yanked into a register, how do I completely replace searched lines matching ‘old target line’?

Answer 1

Use 0y$ to yank your replacement line – this won’t include the newline.

Then use:

%s/.*old target line.*/\=@"

To replace the target lines with the contents of the unnamed register, which will contain the last yank.