## Shell Scripting

A shell script in simply a script that excutes a series of commands written in the script at once from the terminal. This is equivalent to any programming language where you can execute a script from a console.

Linux can come with two types of shells, the C shell and the and Bourne Shell. Since we are using OpenWRT we are only concerned with the latter, which we invoke when we type sh into the command line. At this point, we will write a simple script and explain what will happen at each step during execution. This script uses some general programming techniques. So if you are new to programming, we recommend reading this for an in depth explanation.

Take a look at this example script below, we’ll be working with it soon:

# Anything after the hash symbol is considered a comment.
# This script will create log of the time the script that was executed
# and the name of the person who executed it. The log will be stored in
# a file called log.txt, found in the "/" directory. The script will
# also display the contents of the log.txt file on the terminal.
#The line below tells Linux which shell to use for execution

#!/bin/bash

# Create NAME variable with value name
NAME=name

# Create DATE variable with value date
DATE=date

#Prompt User to input their name

#Store the value entered by the user into the variable username

#Store the value of our username in NAME variable
NAME=$username #The DATE stores the value returned by the date command. in form$(command)
DATE=$(date) #Append the NAME and DATE values to the log.txt file echo$NAME \$DATE >> /log.txt

#Display the contents of the log.txt file
cat /log.txt

Copy the script to the “/” folder in your Omega and save it as LogGen.sh. Run the script by entering this script into terminal and see what happens.

sh LogGen.sh

Run it a few times entering different names and see what happens in the output.

It should look something like this.

The last topic of the Linux Introduction Series introduces the concept of Users, Ownerships and Permission in Linux systems.