bug#22181: endless loop in grep 2.22

[Paul Eggert]

Jim Meyering wrote:
> Hah! TIL head -N and yes are not portable. Thank you.
> I've been spoiled/corrupted by writing coreutils tests for so long.
>
> I would prefer to continue to use "yes" via the following, at least
> in the first test. That way is clearer. In the second, I could go either
> way, since your awk process replaces both yes and head, at the
> expense of being a bit less concise and less readable.

I could go either way too.

Though it's not needed for these particular tests, the shell function can be 
tweaked to default to 'y' and to output quotes and backlashes in the arg as-is, 
like BSD 'yes'.  Something like this, perhaps?

yes() { line=${*-y} ${AWK-awk} 'BEGIN{for (;;) print ENVIRON["line"]}'; }