Learning Linux Shell Scripting - Second Edition

Numerical handling if constructs

Let's learn about using the if construct for numerical decision-making.

We can use the test command for finding which variable contains the smaller value:

$ X=10 
$ y=20 
$ (( x < y )) 
$ echo $? 
0 
The result 0 shows that x is smaller than y. 

In the shell script if_01.sh, we can use the test command along with the if construct for checking the equality of variables with numerical values as follows:

#!/bin/bash 
a=100 
if [ $a -eq 100 ] 
then 
    echo "a is equal to $a" 
else 
        echo "a is not equal" 
fi 

Let's test the following program:

    $ chmod +x if_01.sh
    $ ./if_01.sh
  

The following will be the output after executing the preceding commands:

    a is equal to 100
  

Use the script if_02.sh to check which product is costly. ...