GNU bug report logs - #6393
The meaning of --key of sort command?

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From: Peng Yu <pengyu.ut <at> gmail.com>
To: 6393 <at> debbugs.gnu.org
Subject: bug#6393: The meaning of --key of sort command?
Date: Thu, 10 Jun 2010 11:39:11 -0500

Hi,

I don't think that I completely understand what key means. In the
following example, I thought that --key=2 should order the lines by
the 2nd letter in each line without reordering the lines with the same
2nd letter. But it turns out my understanding is not correct. For
example, "u a" was before "a a" sorting, but "u a" is after "a a"
after sorting.

According to the man page, I'd think the sorting is based on the 2nd
column only but the 1st column. Why the 1st column matters in this
case?

-k, --key=POS1[,POS2]
              start a key at POS1 (origin 1), end it at POS2 (default  end  of
              line)


$ cat input.txt
u a
c c
a a
e e
p a
m e
a a
l e
a a
$ sort --key=2 input.txt
a a
a a
a a
p a
u a
c c
e e
l e
m e


-- 
Regards,
Peng

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