GNU bug report logs - #6124
basename/dirname are not POSIX compliant on arg starting with a dash

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Message #11 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Vincent Lefevre <vincent <at> vinc17.net>
To: Pádraig Brady <P <at> draigBrady.com>
Cc: bug-coreutils <at> gnu.org, 580492 <at> bugs.debian.org
Subject: Re: bug#6124: basename/dirname are not POSIX compliant on arg
	starting with a dash
Date: Thu, 6 May 2010 15:23:38 +0200

On 2010-05-06 13:50:27 +0100, Pádraig Brady wrote:
> The above busybox behavior implies that
> if you write a robust script like this for coreutils,
> that it is not portable to busybox:
> 
> base=$(basename -- "$path")

If one follows POSIX, the correct way to do it is:

  base=$(basename "$path")

and this is robust because the first argument is necessarily the path
(it cannot be an option, even "--").

> That also implies that we can't change the behavior.

According to

  grep 'basename --' /usr/bin/*
  grep 'basename \$' /usr/bin/*

on my Debian machine, almost all scripts use basename without "--".
The only exceptions are autoconf (but I'm not sure this counts, as
there's a test for "basename --" first, and I don't know what it
really expects) and savelog (from the debianutils package, thus
specific to Debian, but savelog also uses `basename $0`, so that
it is already inconsistent). Therefore I assume that changing
coreutils would be easier.

> Because there is an optional suffix parameter, one can't
> know which behavior is required for the above example.
> I suppose one could choose based on POSIXLY_CORRECT.

I think that it should really behave correctly if POSIXLY_CORRECT
is set, but also if it isn't set, given what appears to be the
current practice.

> Note solaris behaves like busybox and openbsd behaves like coreutils.

Perhaps they're copying coreutils without looking at what POSIX says.

-- 
Vincent Lefèvre <vincent <at> vinc17.net> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)

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