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[sed] Run and understand Replace newline at the end of each line

created-2026/01/04 updated-2026/03/25

Introduction

This repository runs a sed command to replace newlines at the end of lines in a file with another character and displays it in the terminal.

The commands you need to install

  1. git

Quickstart

If you have already installed the above command, run the following command to download it from the repository, then change the directory and run the sed command to check the output.

ubuntu

git clone https://github.com/trygfmi/sed_replace-end-of-line
cd sed_replace-end-of-line
cat test.txt
sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/ /g' test.txt
Output results
aaa bbb

macos

MacPorts

source ~/bashrc_folder/macports_alias
git clone https://github.com/trygfmi/sed_replace-end-of-line
cd sed_replace-end-of-line
cat test.txt
sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/ /g' test.txt
Output results
aaa bbb

windows

WSL2

git clone https://github.com/trygfmi/sed_replace-end-of-line
cd sed_replace-end-of-line
cat test.txt
sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/ /g' test.txt
Output results
aaa bbb

MSYS2 MINGW64

git clone https://github.com/trygfmi/sed_replace-end-of-line
cd sed_replace-end-of-line
cat test.txt
sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/ /g' test.txt
Output results
aaa bbb

Procedure

ubuntu

Click to open details

Advance confirmation

Enter the following command into the terminal and if command not found does not appear, it’s OK.

git --version

preinstall

Please install the command that shows “command not found” in the terminal using the following command.

sudo apt install git

command

Executing the following command in the terminal should output a string similar to the following:

git clone https://github.com/trygfmi/sed_replace-end-of-line
cd sed_replace-end-of-line
cat test.txt
sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/ /g' test.txt
Detail
aaa bbb

macos

Click to open details

Advance confirmation

Enter the following command into the terminal and if command not found does not appear, it is OK.

source ~/bashrc_folder/macports_alias
git --version

*MacOS uses the MacPorts package manager to manage commands. If you haven’t installed it yet, please refer to the MacPorts installation instructions at the link below. Also, set an alias for the command so that you can call the command without conflicting with the existing environment. If you are using this blog for the first time, please refer to the following two articles to set up your environment.

preinstall

If the command not found appears in the terminal, install it using the following command and set an alias.

sudo port install git
echo 'alias git="/opt/local/bin/git"' >> ~/bashrc_folder/macports_alias

command

Executing the following command in the terminal should output a string similar to the following:

source ~/bashrc_folder/macports_alias
git clone https://github.com/trygfmi/sed_replace-end-of-line
cd sed_replace-end-of-line
cat test.txt
sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/ /g' test.txt
Detail
aaa bbb

windows

Click to open details

Advance confirmation

Enter the following command into the prompt and if command not found does not appear, it’s OK.

WSL2
git --version
MSYS2 MINGW64
git --version

*Windows has been confirmed to work with WSL2 and MSYS2 MINGW64. Please install WSL2 if possible, and if you are unable to set it up, you can run it by installing MSYS2, but there may be some commands that can only be run in WSL2. Please refer to the following article for instructions on how to install WSL2 and MSYS2.

preinstall

If the command not found appears in the prompt, please install it using the following command.

WSL2
sudo apt install git
MSYS2 MINGW64
pacman --sync git

command

By executing the following command at the prompt, you should get the following output:

WSL2
git clone https://github.com/trygfmi/sed_replace-end-of-line
cd sed_replace-end-of-line
cat test.txt
sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/ /g' test.txt
Detail
aaa bbb
MSYS2 MINGW64
git clone https://github.com/trygfmi/sed_replace-end-of-line
cd sed_replace-end-of-line
cat test.txt
sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/ /g' test.txt
Detail
aaa bbb

Afterword

Define label a with :a, save the next line in the work area to be replaced with N, and if it is not the end of the line, jump to label a. Repeat this process until all lines are saved in the work area, then execute the replacement, replacing the newline at the end of each line with another character.

List of how to use the sed command

There are other articles about the sed command besides this one.
Please check them out at the link below if you’re interested.

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