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

Follow-up Comment #2, sr #110657 (project autoconf):

>> For example, grep does not support -e , but egrep does.
> AC_PROG_GREP looks for a grep that does support -e, so a configure script
that uses that should have a $GREP that works, assuming you have one somewhere
in your $PATH. (If not, you'll need to get one.)

Unfortunately, my configure script does not use AC_PROG_GREP directly.

Instead, this is brought in via AC_REQUIRE by AC_PROG_EGREP, which itself is
required by AC_EGREP_CPP which is required by lots of tests for header files
etc.

However, as said in my initial report, grep is actually not used further down
in the script (AC_PROG_CPP only needs egrep, not grep). And strangely enough,
egrep *does* support the -e flag on UnixPC.

>> This lack of support of -e makes the configure script fail, although there
is a usable egrep.
> Autoconf's 'configure' script doesn't use 'grep -e' anywhere that I can
see.

And that is exactly my point. Absence of a feature which is not being used
anywhere shouldn't be a fatal error.

> Are you debugging some other 'configure' script that uses 'grep -e'?

No, I've only been debugging the mtools configure script (generated by
autoconf) as well as another configure script generated by autoconf from a
mostly empty configure.in

> If so,it should use AC_PROG_GREP

I'm not really sure how adding an explicit AC_PROG_GREP would solve the
problem brough by the implicit usage (due to AC_REQUIRE, see above)

> and "$GREP -e" and you should have a grep in your $PATH that works.

Unfortunately, this museum piece :-) doesn't have a grep where -e works, but
it *does* haven an egrep that supports -e. The issue I have is that the
configure script *doesn't* actually *need* a grep that supports -e (apart from
this test itself), and only needs egrep with -e. Neither does my own
compilation need grep -e.

(I just hope you didn't get confused by the existence of an -E (capital E)
option that makes grep behave like egrep (i.e. uses extended regexp syntax).
The -e that I am talking about here is lower case -e that makes allows to use
regular expressions that start with a dash (-), or to use multiple regular
expressions)



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