Conditionals in Shell Programming

Conditional statements in Linux Shell Programming allow scripts to make decisions based on conditions. These are integral part of any programming language and just like other languages such as C, Python, JavaScript, Linux Shell also provides conditional statements. A conditional statement can be defined as an integral part of the shell script which guides the interpreter into the correct path of execution depending on the given conditions.

In shell, the main commands that are used for conditionals statements are if, elif (else if), and else. These commands are used for process control based on the results of conditional tests which can evaluate the value of string variables, arithmetic tests, or the status of a process.

Here's a simple illustration of how they work:

#!/bin/sh
a=10
b=20

if [ $a -lt 20 ]
then
   echo "a is less than b"
elif [ $a -gt 20 ]
then
   echo "a is greater than b"
else
   echo "a is equal to b"
fi

In the above script, the condition inside the if statement is being checked. If the condition is true, then the code block inside the if statement gets executed, otherwise, it moves to the elif condition and so on. If none of those conditions is satisfied, then the code block inside the else statement will be executed.