First I want to bring your attention to this men :

$?

This is widely used to catch the status of the execution of any command. If is a decent command must be return zero for a success and a nonzero value for error, failure, etc. I said decent because some tools like some option of curl or sqlplus, does not do that T_T

Success & Non Success

if you add $? exactly before of your line, you can get the exit status of that line. For example :

If your command is:

ls 145

Console message is : ls: cannot access ‘145’: No such file or directory

And if you execute this :

echo $?

Console shows you : 2. Which means an error, failure or something that did not end well.

But if your command is :

ls /tmp

And /tmp exist, console shows you a list of files and folders inside /tmp. And $? will have a 0 value which means success.

Here another example:

This is, unfortunately, not always the case

Some tools like sqlplus in case of success or error return 0 value. In this case, stdout or console message returned are the only way to detect if some command ends with success or failure.

Script mode

page_detect() {
  curl github.com
  status=$?
}

echo "exit status of curl command is:$(page_detect)"

or

STATUS=$(page_detect)

if [ $STATUS -eq 0 ]; then
	printf "success"
else
	printf "failed"
fi

That’s it for today.

Until the next,
JRichardsz