On Sun, Nov 13, 2016 at 5:56 PM, Gary Johnson <garyj...@spocom.com> wrote: > There was some recent discussion on the vim_dev list of a failure to > update a Vim package which was found to be due to an update of grep > from 2.25 to 2.26. The details of the grep behavior are discussed > here: > > https://www.linuxquestions.org/questions/slackware-14/pkgtools-grep-bug-in-slackware[64]-current-4175593054/ > > In short, it seems to be due to the "grep: /dev/null output > speedup" commit of 2016-05-01, af6af288eac28951b5eee1eaaf373e22b2193b7b. > When grep terminates early, it closes the pipe it's reading stdin > from, which terminates the program on the other side of that pipe > early, before that program has completed its task. > > Oops.
Thank you for the report. Oops, indeed. While I see nothing in the POSIX specification (http://pubs.opengroup.org/onlinepubs/9699919799/utilities/grep.html) that requires it to read all input in such a case, I think the current behavior violates least-surprise. Here is an example to demonstrate. I believe that POSIX does not dictate what this code prints: grep-2.25: $ (seq 10000000; echo $? 1>&2) | grep . > /dev/null 0 grep-2.26: $ (seq 10000000; echo $? 1>&2) | grep . > /dev/null 141 Paul, what do you think about making your heuristic apply only for non-pipes?
