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The 
-eq
 portion of the command is similar to 
==
 in most programming languages. It's 
checking to see whether the value is equal to something. Alternatively, we can use 
-ne
 (not equal), 
-gt
 (greater than), 
-ge
 (greater than or equal to), 
-lt
 (less than), and 
so on.
At this point, I recommend you take a break from reading to further practice 
scripting (practice is key to committing concepts to memory). Try the following 
challenges:
•  Ask the user to enter input, such as their age, and save it to a variable. If the 
user enters a number less than 30, tell them they're young. If the number is 
equal to or greater than 30, 
echo
 a statement telling them that they're old.
• 
Write a script that copies a file from one place to another. Make the script 
check to see whether that file exists first, and have an 
else
 statement printing 
an error if the file doesn't exist.
•  Think about any topic we've already worked on during this book, and 
attempt to automate it.
Now, let's take a look at another concept, which is looping. The basic idea behind 
looping is simply doing something repeatedly until a condition has been met. 
Consider the following example script:
#!/bin/bash
myvar=1
while [ $myvar -le 15 ] 
do 
    echo $myvar 
    ((myvar++)) 
done 
Let's go through the script line by line to understand what it's doing.
myvar=1 
With this new script, we're creating a control variable, called 
myvar
, and setting it 
equal to 
1
:
while [ $myvar -le 15 ]

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Chapter 6