Linux and Unix Shell Programming

18.3. if then else statements

The if statement lets you test for a condition. Based on the true (0) or false (1) return of a test, a series of statements can then be performed. The construct of the if statement makes it ideal for error checking. Here’s the format of the if statement:

if condition1 then   commands1 elif condition2 then   commands2 else   commands3 fi 

Let’s break down this if statement to see what’s really going on.

if condition1	If condition1 is true
then	then
commands1	do the commands1
elif condition2	if condition1 is not met
then	then
commands2	do the commands2
else	if condition1 or condition2 is not met
commands3	then do commands3
fi	finish

The if statement must be terminated with the word fi. Leaving out the closing fi ...