SORT bug: multiple field sort

[Denzen, van Carl]

On a quite fresh ubuntu with sort version  6.10, when I do a quite simple sort, 
I get unexpected result.
Fields are variable length, separator is comma. I want to sort on two date 
fields, but for simplicity I treat them as normal ascii. Here is the output:
address@hidden carl]$ cat test-input.txt
23-01-1999,25-04-2008
,24-04-2008
23-01-1993,23-04-2008
,01-02-1999
,12-03-1998
23-01-1991,21-04-2008
address@hidden carl]$ sort <test-input.txt --field-separator=, --key=1.7,1.10 
--key=1.4,1.5 --key=1.1,1.2 --key=2.7,2.10 --key=2.4,2.5 --key=2.1,2.2
,01-02-1999
,12-03-1998
23-01-1991,21-04-2008
23-01-1993,23-04-2008
23-01-1999,25-04-2008
,24-04-2008

I expected the record with date 12-03-1998 to sort before the record with date 
12-03-1998.
What am I doing wrong? Or is sort doing something wrong (like walking out of 
field #1 and sorting on parts of field #2)?
I did read the FAQ about locale issues and I did set LC_ALL to C (export 
LC_ALL="C"). Same unexpected result.

Carl.

Carl van Denzen
Applicatie consultant
Healthcare Sector

PinkRoccade Healthcare b.v.
Wolga 5
2491 BK  Den Haag
The Netherlands

M: +31 (0)6 2952 8914 (ma/di/wo/do)
E: address@hidden<mailto:address@hidden>

PinkRoccade Healthcare b.v. Handelsregister 27322973 te Den Haag



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