regex-cheatsheet | Cheatsheet for different regex syntaxes | Regex library

I am playing bandit from overthewire.org; getting to level 10 requires me to find strings preceded with several "=" characters (equal sign) (I interpreted "several" as "two or more") in a text file.

The target lines look like this:

========== passwordhere123

i.e. ten equal signs, one space, and a string of letters and numbers, followed by line break (not sure which exact type).

These lines should be excluded:

c========== EqualSignDidNotStartLine

= only-one-equal-sign

equalsign=somewhereElse

No equal signs at all

The original data did not contain any lines preceded by less than ten but more than one ='s; there are some +'s (plus signs) littered in the text, but +'s and ='s are never in the same line.

The bandit server runs some kind of linux @ 4.18.12 (uname -r), GNU bash 4.4 (from man page), and GNU grep 2.27 (from man page).

The raw data contains non-readable parts, so it is fed through strings first to leave only human-readable strings fro grep to process.

From what I learned, grep's default regex engine (BRE, thanks Casimir) should not be too different from PCRE's. * is still a quantifier (match the preceding pattern zero times or more), not as a standalone pattern meaning "anything, zero times or more". This confuses me in grep's behavior below.

Edit: per this chart, "+" needs to be escaped (i.e.\+) in BRE. It does not help though. I will make some more testing strings to try to decipher what's going on.

Here's the command I tried: