<aside> 💡 Like in many other languages, Bash has conditions to easily behave differently given a certain condition. The conditions in Bash are the if/else clause and a case. Indentation is important when writing your clauses multiline and when writing single line clauses, they need to be delimited by a semicolon.

</aside>

If/Else Clause

You denote that this clause ends by typing fi. Be sure to place a semicolon after the assertion, followed by then to create a correct clause. A simple if/else clause can be formed by asserting a condition and performing the command if the condition resolves truthy:

if grep "Detail" ouput.log; then
	echo "Contains Detail in ouput.log"
else
	echo "No Detail in output.log"
	return 1
fi

• There is of course also the else if statement to assert additional conditions and react differently if the first condition does not resolve but the second one does:

In the examples above only commands are being used to assert a condition. If you remember expressions from 1. What is Bash they will come in handy here. Since expressions are evaluated inline they can easily be used in an if/else clause:

if [[ -f index.js ]]; then
	cat index.js
else
	echo "No index.js file"
fi

# You could also write the above as shorthand:
if [[ -f index.js ]]; then cat index.js; else echo "No index.js file"; fi

Case

Cases can be used to assert a lot of conditions at once, not having to write a tedious repeated elif. The syntax for cases is somewhat difficult, there is:

• the *) catch-all case which is used as a default when no other cases match
• ;; to break out of a case. Always break out of a case or you're in for trouble, since cases cascade

case "$OPTIONS" in
    "force")
			echo "Force option is enabled."
			run_main_pipeline "FORCE"
    ;;
    "debug")
			echo "Debug mode enabled."
			run_main_pipeline "DEBUG"
    ;;
    "dry-run")
			echo "Doing a dry run"
			exit 0
    ;;
    *)
        echo "No options enabled."
				run_main_pipeline
    ;;
esac

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