[SOLVED] What does the [[ -z "$PORT" ]] && export PORT=8080 bash command do?

Issue

I am following a tutorial and they use the command [[ -z "$PORT" ]] && export PORT=8080 and I don't fully understand what it's doing. My knowledge of bash commands is very basic and so I am not even sure what to google to figure this out.

The little knowledge I have suggests to me that this somehow checks if the env variable PORT is set and if not set it to 8080. However, I don't actually understand what is going on, except for the last part, export PORT=8080.

Could anyone explain what the different operations are doing here?

Solution

Here is what is going on -

• [[ -z "$PORT" ]] is checking whether the length of the string in variable "$PORT" is zero or Not.
• the second part of && is only evaluated if the first part is true.

So short answer is this -

if the length of the string "$PORT" is zero then it will export a variable named PORT which will have the value of 8080 otherwise it will not export the variable and will moved on to the next statement in bash script.

Answered By - y.kaf.

Answer Checked By - Timothy Miller (WPSolving Admin)