> On Apr 7, 2018, at 1:59 AM, J Doe <gene...@nativemethods.com> wrote: > > Ah, interesting - that must be it, then. > > This is on an Ubuntu 16.04 LTS server. I can see the dependencies compiled > in from Ubuntu’s page  and GNU libc is listed.  seems to suggest that > regular expressions are part of GNU libc. > > Is there another way I can confirm that ?
FreeBSD 11 (POSIX): $ echo "1 b" | egrep '\d\s\w' $ MacOS High Sierra (POSIX with GNU or similar extensions): $ echo "1 b" | egrep '\d\s\w' 1 b $ Your Ubuntu system most likely will match the MacOS results. Which means that your regexp table is not portable, but happens to work on your system. -- Viktor.