Ruby: You can nest regular expressions

Percent Notation

We already know that that we can create strings using the percent notation:

%(<foo="bar's ton">) is perfectly fine Ruby.

Modifier

Bu...

I have a container of regular expressions. I'd like to analyze them to determine if it's possible to generate a string that matches more than 1 of them. Short of writing my own regex engine with this use case in mind, is there an easy way in C++ o...

Regular expressions can have something called "zero-width look-behind assertions". This means that you want a pattern to be preceded by another pattern, but not include the preceding pattern in your match or search cursor. E.g. (?<=x)y matches `...

The following two hints are taken from Github's Ruby style guide:

If your regular expression mentions a lot of forward slashes, you can use the alternative delimiters %r(...), %r[...] or %r{...} instead...

Ruby's regular expressions can be represented differently.
When serializing them, you probably want to use inspect instead of to_s.

For the examples below, consider the following Regexp object.

regexp = /^f(o+)!/mi

to_s

Using ...

So you have a method returning a regular expression but one case that should not yield a matching Regexp object but still keep the API stable? Just return one that never matches:

/(?!)/

Two weeks ago, Cloudflare was struck by a global outage that lasted ~30 minutes. The incident was rooted on a CPU exhaustion caused by a single regular expression containing some [catastrophic backtracking](https://www.regular-expressions.info...

You can write regular expressions some different ways, e.g. /regex/ and %r{regex}. For examples, look here.

Remember that it is always a good idea [to matc...

As far as I know, the only plugin out there that handles this (semantic issue) correctly is Makandra’s Aegis. And they are GERMAN. It functionally works about the same as well. So props to them for that.

Although regular expression syntax is 99% interchangeable between languages, keep this in mind:

• By default, the dot character (".") does not match a line feed (newline, line break, "\n") in any language.
• Some languages allow you to mo...