Re: [bug #17457] "grep -r foo . > somefile" goes into an infinite loop

[Jim Meyering]

Paolo Bonzini wrote:
> Update of bug #17457 (project grep):
>   <http://savannah.gnu.org/bugs/?17457>
>                   Status:                    None => Invalid
>              Open/Closed:                    Open => Closed
>
> Follow-up Comment #4:
>
> Hmm, this cannot be fixed.  By definition the output file can grow
> indefinitely, and grep will have to read it until EOF.

Actually, how about detecting this and diagnosing
the problem rather than falling into the infloop?

This currently evokes an infloop for me:

    $ seq 1000000 > k
    $ grep 111 k >> k

However, simply detecting when the output FD is also an input FD is
not enough, since this variant does not get stuck:

    $ seq 1000 > k
    $ grep 111 k >> k