On 07/30/2013 04:33 PM, Eric Blake wrote:

> It SOUNDS like you are merely asking for a stable sort option.  Have you
> tried the -s/--stable option?  That effectively adds an invisible key of
> last resort that says if two lines otherwise compare equal, sort them so
> that the line occurring first in input also occurs first in output.

An alternative view of how -s works (that more closely matches what you
will see in 'sort --debug' output) is that POSIX requires that 'sort'
behave as if a key of -k1 were always the last key present (if two lines
otherwise compare equal, sort them by a strcoll() comparison of the
entire line), where -s is the GNU extension that disables this POSIX
implicit full-line sort key, so that you are left with a stable sort.

Since 'adding an option to remove a key' sounds a little fishy on the
surface, you can see why I gave my first explanation instead.  But at
the end of the day, all that matters is the result, so pick whichever
mental representation you find easier to understand :)

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org