Question

those reqular expressions drive me crazy. I’m stuck with this one:

test1:[[link]] test2:[[gold|silver]] test3:[[out1[[inside]]out2]] test4:this|not

Task:
Remove all [[ and ]] and if there is an option split choose the later one so output should be:

test1:link test2:silver test3:out1insideout2 test4:this|not

I came up with (PHP)

$text = preg_replace("/\\[\\[|\\]\\]/",'',$text); // remove [[ or ]]

this works for part1 of the task. but before that I think I should do the option split, my best solution:

$text = preg_replace("/\\[\\[(.*\|)(.*?)\\]\\]/",'$2',$text);

Result:

test1:silver test3:[[out1[[inside]]out2]] this|not

I’m stuck. may someone with some free minutes help me? Thanks!

Answer 1

This is impossible to do in one regular expression since you want to keep content in multiple “hierarchies” of the content. It would be possible otherwise, using a recursive regular expression.

Anyways, here’s the simplest, most greedy regular expression I can think of. It should only replace if the content matches your exact requirements.

You will need to escape all backslashes when putting it into a string (\ becomes \\.)

\[\[((?:[^][|]+|(?!\[\[|]])[^|])++\|?)*]]

As others have already explained, you use this with multiple passes. Keep looping while there are matches, performing replacement (only keeping match group 1.)

Difference from other regular expressions here is that it will allow you to have single brackets in the content, without breaking:

test1:[[link]] test2:[[gold|si[lv]er]]
test3:[[out1[[in[si]de]]out2]] test4:this|not

becomes

test1:[[link]] test2:si[lv]er
test3:out1in[si]deout2 test4:this|not