regex - How to delete newline if the line doesn't end with "

Question

Sample data:

"data","123"
"data2","qwer"
"false","234
And i'm the culprit"
"data5","234567"

Output text should be

"data","123"
"data2","qwer"
"false","234And i'm the culprit"
"data5","234567"

In essence, I want to fix my csv file (which is very large)

I'm using sed so an answer in sed would help a lot :)

Answer 1

sed is always the wrong choice for any problem that involves multiple lines. Just use awk:

$ awk '{printf "%s%s", (prev~/"$/?RS:""), $0; prev=$0} END{print ""}' file
"data","123"
"data2","qwer"
"false","234And i'm the culprit"
"data5","234567"

The above just checks if the previous line ended with a " and if it did then it prints the default Record Separator (which is a newline - you could replace RS with ORS or a hard-coded " " if you prefer) but if it didn't then it doesn't print anything. Then it prints the current record without a newline after it. At the end of everything it prints a newline.