[sr #110657] Autoconf configure script considers absence of usable grep a fatal error, although it only uses egrep thereafter

Follow-up Comment #8, sr #110657 (project autoconf):

[comment #6 comment #6:]
> How about the attached patch instead?

Unfortunately, this patch doesn't work ... due to another peculiarity of
UnixPC's egrep which had escaped earlier: for some weird reason, if -e is
used, egrep doesn't support grepping in stdin, but only in files given on
command line.

i.e. egrep -e root </etc/passwd doesn't work.

However, egrep -e root /etc/passwd does work, and so does egrep root
</etc/passwd

There seems no easy fix for it, because the use case (grepping in cpp's
output) does indeed involve grepping from stdin. Catching cpp's output into a
file would be needlessly cumbersome, so we might need to ponder whether -e is
indeed needed for AC_EGREP_CPP. I think we do agree that multiple -e options
are not needed for AC_EGREP_CPP. So the only reason why -e is needed is to
search for strings that start with a dash. But there is another way than -e to
escape that dash: simply put a pair of parenthesis around the search string:

egrep '(-z)' </etc/profile


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