How to search and replace empty line after specific token?

Question

I want to delete newlines after lines containing a keyword e.g. like modifiers private:,public: or protected: to fulfill our coding standard. I need a command line tool (Linux) for this, so please no Notepad++, Emacs, VS, or Vim solutions, if they require user interaction. So in other words I want to do a:

sed -i 's/private:\s*\n\s*\n/private:\n/g'

I've seen this question but was unable to extend it to my needs.

Answer 1

If I understand correctly, you want to remove empty lines which follow a line containing private:, public:, or protected:.

sed ':loop;/private:\|public:\|protected:/{n;/^$/d;Tloop}' inputfile

Explanation:

• :loop create a label
• /private:\|public:\|protected:/ will search for lines containing the pattern.
• n;/^$/d will load the next line (n), check whether it is an empty line (/^$/), and if it is, delete the line (d).
• Tloop branch to label loop if there was no match (line was not empty)

I am no sed guru, there might be more elegant ways to do this. There might also be more elegant ways to do this in awk, perl, python, whatever.