A Quick Introduction to 'Echo'
This is the equivalent of common output commands in most programming language (print or puts statements).
For Example:
echo "Greetings"
This outputs just one word "Greetings" (without the quotation marks).
echo "Greetings $USER, your current working directory is $PWD"
This picks up the values of the environment variables and and displays something like:
Greetings prashantb1984, your current working directory is /home/prashantb1984
The above message, of course, will vary from system to system, depending on the setting of environment variables.
Accepting Inputs
This can be accomplished using the read statement.
read number
echo "The number you have entered is $number"
If the user provides an input 4, the output is:
The number you have entered is 4
Consider this snippet:
read name
echo "The name you have entered is $name"
If the user provides an input Max, the output is:
The name you have entered is Max
Recommended Resources
A quick but useful tutorial for Bash newcomers is here.
Handling input is documented and explained quite well on this page.