I understand that GNU
-E uses basic regex and that
grep -E uses extended regex. Is there any harm in using
grep -E even for situations that would work with plain
Not much. Back referencing is not possible in grep -E, so you cannot match the same text as previously matched by a
(..) capturing group (though some
grep implementations like GNU and BSD
grep allow it as a non-standard extension).
And if you want to match literal braces or parentheses,
+, you now will need to escape them...