(1) Use any editor like vi to write shell script.
(2) After writing shell script set execute permission for your script as follows
syntax:

chmod permission your-script-name

Examples:

$ chmod +x your-script-name
$ chmod 755 your-script-name

Note: This will set read write execute(7) permission for owner, for group and other permission is read and execute only(5).

(3) Execute your script as
syntax:

bash your-script-name
sh your-script-name

./your-script-name

Examples:
$ bash bar
$ sh bar
$ ./bar

NOTE In the last syntax ./ means current directory, But only . (dot) means execute given command file in current shell without starting the new copy of shell, The syntax for . (dot) command is as follows. Syntax:

. command-name

Example:
$ . foo

Now you are ready to write first shell script that will print “Knowledge is Power” on screen. See the common vi command list , if you are new to vi.

$ vi first
#
# My first shell script
#
clear
echo “Knowledge is Power”

After saving the above script, you can run the script as follows:

$ ./first