Re: sort -u -n error : sort v 4.5.3

[Eric Blake]

The most recent stable version of coreutils is 5.94; consider upgrading
(although that does not change your report).

> Sort : the -u (unique) and  -n (numeric) options seem to clash, removing too 
> many lines.
> 
> 
> address@hidden data]# cat /tmp/new_spammers
> 64.202.165.132
> 64.202.165.131
> 64.202.165.133
> 
> 
> address@hidden data]# sort -u < /tmp/new_spammers
> 64.202.165.131
> 64.202.165.132
> 64.202.165.133
> 
> [
> address@hidden data]# sort -n < /tmp/new_spammers
> 64.202.165.131
> 64.202.165.132
> 64.202.165.133
> 
> 
> address@hidden data]# sort -u -n < /tmp/new_spammers
> 64.202.165.132

Not a bug.  This behavior is required by POSIX,
http://www.opengroup.org/onlinepubs/009695399/utilities/sort.html,
which states that -n restricts the key to the first numeric
field, and that -u uniquifies based on the sort key.

In your sample file, the unique key is 64, and all
three lines have the same key.  When -n or -u is
used alone, a tiebreaker is used that sorts based
on the rest of the line.  But when used together,
the behavior correctly stops after one line.

-- 
Eric Blake