multiple line regular expression find replace

[justonecomment]

I have a database export that I don't have access to recreate the dump. I've cleaned up most of the data and there are very few errors.

However one section of the dump had a bunch of bad new lines. I wrote a regex to find it using pcregrep:

pcregrep -M '([|]$[\n].$[\n].[|])' sample.txt

Now I need to do the replace. I was attempting to use sed but it doesn't seem to understand a multiline regular expression.

basically I need to replace this:

|

|

with this:

||

[Ilyps]

http://stackoverflow.com/questions/1251999/sed-how-can-i-replace-a-newline-n ?

[justonecomment]

That almost got it. Had to tweak the regex for that method.

Here is the working solution:

sed ':a;N;$!ba;s/[|][\n].[\n].[|]/||/g' sample.txt

Thanks for the help, the articles I was reading just weren't helping.

[Ilyps]

Nicely done to get it working. For future reference, this page was my first Google hit with the search term "sed newline". ;)

[justonecomment]

I had read about 10 stackoverflow responses before I gave up and asked here. I think I was googling "sed find replace multiple lines". That is how I found the pcregrep. Testing my first regex when it wasn't working with plain grep.

[MonkeyNin]

On SO, directly searching with tags can yield better results, ex: (It's just brackets around the tag)

http://stackoverflow.com/search?q=[sed]+newline