Learn Linux Shell Scripting - Fundamentals of Bash 4.4

if-then-else

By now, you'll hopefully have a feeling for how useful if-then logic is. However, you might feel like something is missing still. If that is the case, you would be right! An if-then construct is not complete without the ELSE statement. The if-then-else construct allows us to specify what should happen if the test in the if-clause does not equal true. Semantically, it could be translated as:

IF condition, THEN do-something, ELSE (otherwise) do-something-else

We can illustrate this very easily by taking one of our earlier scripts, if-then-exit.sh, and optimizing both the flow of the script and the code:

reader@ubuntu:~/scripts/chapter_09$ cp if-then-exit.sh if-then-else.shreader@ubuntu:~/scripts/chapter_09$ vim if-then-else.sh ...