Question

I have the following conditions for my regex :
When the string is not empty it should contain the word “internal”

So in other words :

"<link linktype='internal' id='{F88AE8AE-69C4-4E31-95BF-73B110FEE63A}' />" --> OK
"<link linktype='external' id='{F88AE8AE-69C4-4E31-95BF-73B110FEE63A}' />" --> NOK
"test" --> NOK
"" --> OK

I know that an empty string can be checked with : ^$
Or a non empty string with : ^\s*\S
and my internal check simply as : linktype=\'internal\' (for example)

Bringing them together is the hard part. I’ve been stuck on this, but it doesn’t do as expected :

(?(?=^\s*\S)linktype=\"internal\"|^$)

Can anyone help ?

Answer 1

You could try (^$)|(^.*linktype=\"internal\".*$)

Either the empty string, or a string with the text linktype="internal".