A out-of-expectation output when use both -o and -c option

[larmbr zhan]

Hi, all

When use --only-matching with -c, grep gives a
counter-intuitive output on this input:

$ cat poc.txt
alan cox is a guy.
cox versus cox
cox cool

$ grep -o -c  "cox" poc.txt

What I suppose it to give is 5, but actually 3.

I  checked the manual and found "-c" reports
the number of matching lines. Grep just behaves
correctly :-)

I also checked the POSIX docs and found that POSIX
mandates the '-c' option , but not the '-o' option.
So for the sake of  compliance with the standard,  it *does*
have bias in favor of  -c, and  neglects the -o.

However,I think what an utility behaves should not
surprises its user. We should not blame user that why
don't you read the f*cking manual first to make it work
 correctly.

Naturally, counting  the number of exact matching parts
is a reasonable and quite useful feature.

Since we shouldn't change the semantics of '-c". what should
it do is just give a waring  when user use -c and -o.
and should clarify it in doc, just as what  grep does  when -C(context) and
-o are used together.

I don't know if this is a feasible way; and if it is , I will submit a patch
for this.

---
Larmbr Zhan