bug#9089: pipe failure with cat and head of coreutils 6.12

[Philipp Thomas]

* Pádraig Brady (address@hidden) [20110715 16:20]:

> Note the reason ksh does this, is to allow commands
> to efficiently inspect the input, rather than reading byte by byte.
> This is related to the recent `stdbuf -i0` discussions.

And that noticeable speedup is one of ksh's main advantages, at least
according to our ksh maintainer.

> Note it seems to be timing dependent whether ECONNRESET or EPIPE is returned.
> To get ECONNRESET reliably I need to:
> 
> ksh -c "strace yes | (sleep 1; head -n10) > /dev/null"

As far as I've come in tracing the failure is in gnulibs full_write and
neither simple_cat nor full_write seem to have any handling for either error
code.

Philipp