Thanks.  I guess I misinterpreted "uses a default key of the entire line"
as "uses the entire line as keys by default", in which case if the first column
was equal, it would compare the second, then the third, etc.

I guess I don't know what "default key of the entire line" means with respect to -n,
since it apparently didn't treat "1    12" as "112" and "1   4" as 14.
I'm curious to find out what this phrase means in this context.

Roger Christman

On Sun, Aug 21, 2011 09:55 PM, Bob Proulx <bob@proulx.com> wrote:

tags 9334 + notabug
thanks

ROGER GRAYDON CHRISTMAN wrote:
> First: some version information:
> sort (GNU coreutils) 8.4

Thanks!

> I run a series of pipes, and after piping into 'sort -n', I see this: 
>     1   12
>     1    4
>     5   16
>     9   20
> 
> The first column sorted correctly, numerically, but the second did not.
> I do not have sufficient data to determine whether the second column
> is sorted lexicographically, or simply ignored.

Thanks for the report but you are not seeing a bug in sort but in the
use of it.  You have insufficiently qualified the sort criteria.  Try
this:

  sort -n -k1,1 -k2,2

Or my preference:

  sort -k1,1n -k2,2n

The reasoning is as found in the sort documentation:

     A pair of lines is compared as follows: `sort' compares each pair of
  fields, in the order specified on the command line, according to the
  associated ordering options, until a difference is found or no fields
  are left.  If no key fields are specified, `sort' uses a default key of
  the entire line.  Finally, as a last resort when all keys compare
  equal, `sort' compares entire lines as if no ordering options other
  than `--reverse' (`-r') were specified.  The `--stable'
(`-s') option
  disables this "last-resort comparison" so that lines in which all
  fields compare equal are left in their original relative order.  The
  `--unique' (`-u') option also disables the last-resort comparison.
  ...
  `-n'
  `--numeric-sort'
  `--sort=numeric'
       Sort numerically.  The number begins each line and consists of
       optional blanks, an optional `-' sign, and zero or more digits
       possibly separated by thousands separators, optionally followed by
       a decimal-point character and zero or more digits.  An empty
       number is treated as `0'.  ...

Since no fields are specified sort is using a default key of the
entire line.  Since you care about sorting on fields you should
include sort field options.

Bob