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[Shell Script] Run and understand conditional branching using if and else

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

Introduction

This repository executes a program that executes an if else statement in a shell script and branches depending on whether the input string is ok or not.

Commands that need to be installed

  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, run the shell script, enter some characters, and check the output.

ubuntu

git clone https://github.com/trygfmi/shellscript_if-else


cd shellscript_if-else


cat start_shellscript_if-else.sh


chmod 744 start_shellscript_if-else.sh


./start_shellscript_if-else.sh #ok

 

./start_shellscript_if-else.sh #hello
Output results 
user_input_string:ok 

other:hello

macos

MacPorts

source ~/bashrc_folder/macports_alias


git clone https://github.com/trygfmi/shellscript_if-else


cd shellscript_if-else


cat start_shellscript_if-else.sh


chmod 744 start_shellscript_if-else.sh


./start_shellscript_if-else.sh #ok

 

./start_shellscript_if-else.sh #hello
Output results 
user_input_string:ok 

other:hello

windows

WSL2

git clone https://github.com/trygfmi/shellscript_if-else


cd shellscript_if-else


cat start_shellscript_if-else.sh


chmod 744 start_shellscript_if-else.sh


./start_shellscript_if-else.sh #ok

 

./start_shellscript_if-else.sh #hello
Output results 
user_input_string:ok 

other:hello

MSYS2 MINGW64

git clone https://github.com/trygfmi/shellscript_if-else


cd shellscript_if-else


cat start_shellscript_if-else.sh


chmod 744 start_shellscript_if-else.sh


./start_shellscript_if-else.sh #ok

 

./start_shellscript_if-else.sh #hello
Output results 
user_input_string:ok 

other:hello

Procedure

ubuntu

Click to open details

Advance confirmation

Enter the following command into the terminal and if command not found does not appear, it is 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/shellscript_if-else


cd shellscript_if-else


cat start_shellscript_if-else.sh


chmod 744 start_shellscript_if-else.sh


./start_shellscript_if-else.sh #ok

 

./start_shellscript_if-else.sh #hello
Detail 
user_input_string:ok 

other:hello

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.

[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.

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/shellscript_if-else


cd shellscript_if-else


cat start_shellscript_if-else.sh


chmod 744 start_shellscript_if-else.sh


./start_shellscript_if-else.sh #ok

 

./start_shellscript_if-else.sh #hello
Detail 
user_input_string:ok 

other:hello

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.

[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
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/shellscript_if-else


cd shellscript_if-else


cat start_shellscript_if-else.sh


chmod 744 start_shellscript_if-else.sh


./start_shellscript_if-else.sh #ok

 

./start_shellscript_if-else.sh #hello
Detail 
user_input_string:ok 

other:hello
MSYS2 MINGW64
git clone https://github.com/trygfmi/shellscript_if-else


cd shellscript_if-else


cat start_shellscript_if-else.sh


chmod 744 start_shellscript_if-else.sh


./start_shellscript_if-else.sh #ok

 

./start_shellscript_if-else.sh #hello
Detail 
user_input_string:ok 

other:hello

Afterword

The first code below will cause an error because there is no space between [” and “], as in [“$user_input_string” == “ok”]. The second code below will cause an error because there is no space between if and [, as in if[ “$user_input_string”==”ok” ].

read -p "ok or other: " user_input_string


if ["$user_input_string" == "ok"]; then


    echo "user_input_string:ok "


else


    echo "other:""$user_input_string"


fi
read -p "ok or other: " user_input_string


if[ "$user_input_string"=="ok" ]; then


    echo "user_input_string:ok "


else


    echo "other:""$user_input_string"


fi

The code below works fine even though there is no space between “=” and “=”

read -p "ok or other: " user_input_string


if [ "$user_input_string"=="ok" ]; then


    echo "user_input_string:ok "


else


    echo "other:""$user_input_string"


fi

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