Shell deletes empty or blank lines in the file.

Today, we found that there are too many empty lines in a file and we intend to delete them.

So I used SED and checked the command to write it like this:

Sed '/^ $/d' file1

I found that there are still a lot of blank lines in the output content, which is inexplicable.

So: sed '/^ $/P' file1 found that there are few empty rows output, but actually there are many empty rows.

So Cat-A file1 is used.

It was found that many rows contain space characters, which causes regular expressions to not recognize empty rows.

So modify it to: sed '/^ * $/d' file1. Then OK.

In addition, note that the line break in Windows is ^ m $

In Linux, $ is used. If it is a file in Windows, it needs to be converted. It seems like this tool is used to use doc2unix.