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Re: mistake in sort -k argument processing?

From: Andreas Schwab
Subject: Re: mistake in sort -k argument processing?
Date: Fri, 22 Dec 2006 17:55:18 +0100
User-agent: Gnus/5.110006 (No Gnus v0.6) Emacs/22.0.91 (gnu/linux)

Evan Hunt <address@hidden> writes:

>> POSIX specifies that that character position (if present) shall be
>> positive for the field start spec and non-negative for the field end spec
>> (with zero denoting the last character of the field).  Thus GNU sort is
>> behaving correctly.
> Ah, okay, thanks.
> Bit of a doc problem in "info sort", then:
> `-k POS1[,POS2]'
> `--key=POS1[,POS2]'
>      Specify a sort field that consists of the part of the line between
>      POS1 and POS2 (or the end of the line, if POS2 is omitted),
>      _inclusive_.  Fields and character positions are numbered starting
>      with 1.       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>      ^^^^^^
> ...so I figured the 0 wasn't supposed to be allowed.

That does not contradict the use of 0 to describe the special case of the
_last_ character (which has a varying, non-zero position in every field).

> It seems to me that the principle of least surprise would mandate
> that .0 in a position spec should either be the equivalent of not
> setting a character offset, *or* that it should mean the "zeroth"
> character of the field (which would be an error)...

There is no such thing as a "zeroth" character in the position counting.
For the start field you cannot denote the last character, so using 0 does
not make sense.


Andreas Schwab, SuSE Labs, address@hidden
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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