[droithomme]

Grep is used in hundreds of millions of scripts ranging from mundane rarely used things to install scripts to critical system functionality run every few minutes.

It's not acceptable to break the default way it works under any circumstances.

[jasomill]

I agree in principle, though to be fair most UNIX utilities have so many incompatible variants that striving for maximum backwards compatibility often does more harm than good (like producing options that do entirely different things in the presence of other options, in the absence of a leading hyphen, etc.). Practically speaking, sysadmins generally use more consistent tools (e.g., Perl) for nontrivial cross-OS things once this becomes an issue, and, as a developer, it's not clear to me that build-time dependence on, say, Perl or Python is any worse than depending on GNU versions of basic UNIX tools, the existence of which tends to only be a safe assumption on Linux. On non-UNIX platforms, this is an even bigger issue: I'd certainly rather recommend ActivePerl or the latest binary Python 2.7.x release from python.org to the average Windows developer than any of SFU, Cygwin, or MSYS (and I say this as someone with a strong UNIX background who works with both Windows and Windows developers on a daily basis).