In the command line, a shell script is an executable file that contains a set of instructions that the shell will execute. Its main purpose is to reduce a set of instructions (or commands) in just one file. Also it can handle some logic because it’s a programming language.

How to create it

Create the file:

$ touch myscript.sh

Add a shebang at the start of the file. The Shebang line is responsible for letting the command interpreter know which interpreter the shell script will be run with:

$ echo "#!/bin/bash" > myscript.sh
# or
$ your-desired-editor myscript.sh
# write at the first line #!/bin/bash

Add some commands:

$ echo "echo Hello World!" >> myscript.sh

Give the file execution mode:

$ chmod +x myscript.sh

Execute it!

$ ./myscript.sh
Hello World!

More info about shell-scripting can be found here

More info on shell scripting and Linux: