This happens with GNU grep version 2.20 and PCRE 8.35 on Mac OS X. The following command reproduce the problem:
$ printf 'j\x82\nj\n' | grep -P j invalid UTF-8 byte sequence in input But I usually encounter this when recursively searching through files and encountering a binary file which contains invalid UTF-8 sequence. If binary file with invalid UTF-8 sequence is encountered first (without any other matches), grep will abort the entire recursive search and not even mention which file caused the error. This is somewhat confusing when you first encounter it. By the way, this works in GNU grep 2.18 without any errors (you get messages like binary file x matches), and with PCRE 8.33 or 8.35 (I have not tried any other combinations).
