Bash Shell Scripting/Prerequisites
You will need to have Bash installed on your system. It is recommended that you use a GNU/Linux based distribution like Ubuntu, Manjaro, etc. These have Bash installed by default.
If you are using a Unix-like operating system like FreeBSD or MacOS and Bash shell is not installed as default, you can install Bash from their package manager or use their default shell which have Bash support.
If you are on a Windows 10 or Windows 11 system, you can install Windows Subsystem for Linux. If you are on an older machine and don't have SSH access to a GNU/Linux or Unix system, you will probably find it easiest to make use of this book if you are using something like Cygwin, which has not only Bash but also many other common utilities, than if you are using a Bash port for Windows that includes only Bash. If you have Cygwin, just make sure that the directory containing those utilities — likely something like
C:\Cygwin\bin — is listed in your Windows path.
On Android, an app called Termux can be installed.