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string cat

[cat] Run and understand Output variable string with heredoc

created-2025/12/12 updated-2026/03/15

Introduction

This repository executes the cat command to expand the variables written in the here document and write them to a file.

The commands you need to install

  1. None in paticular

Quickstart

Run the cat command and output the string to a file.

ubuntu

hello="hello here document world"


cat << EOF > test.txt


$hello


EOF

 

cat test.txt
Output results 
hello here document world

macos

MacPorts

hello="hello here document world"


cat << EOF > test.txt


$hello


EOF

 

cat test.txt
Output results 
hello here document world

windows

WSL2

hello="hello here document world"


cat << EOF > test.txt


$hello


EOF

 

cat test.txt
Output results 
hello here document world

MSYS2 MINGW64

hello="hello here document world"


cat << EOF > test.txt


$hello


EOF

 

cat test.txt
Output results 
hello here document world

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.

Nothing in paticular

preinstall

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

Nothing in paticular

command

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

hello="hello here document world"


cat << EOF > test.txt


$hello


EOF

 

cat test.txt
Detail 
hello here document world

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.

Nothing in paticular

*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.

[macos] Steps to install MacPorts
[macos] Setting aliases for commands installed with MacPorts

preinstall

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

Nothing in paticular

command

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

hello="hello here document world"


cat << EOF > test.txt


$hello


EOF

 

cat test.txt
Detail 
hello here document world

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
Nothing in paticular
MSYS2 MINGW64
Nothing in paticular

*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.

[windows] Steps to install WSL2 (Windows Subsystem for Linux)
[Windows] Steps to install msys2

preinstall

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

WSL2
Nothing in paticular
MSYS2 MINGW64
Nothing in paticular

command

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

WSL2
hello="hello here document world"


cat << EOF > test.txt


$hello


EOF

 

cat test.txt
Detail 
hello here document world
MSYS2 MINGW64
hello="hello here document world"


cat << EOF > test.txt


$hello


EOF

 

cat test.txt
Detail 
hello here document world

Afterword

cat << EOF > test.txt uses the cat command to output the string from the next line until EOF appears, and outputs the result to the file written to the right of >. You can specify any string for EOF, so try entering the following code.

cat << aaa > test2.txt


test file


aaa

 

cat test2.txt

The string “test file” should be output.

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