[Toybox] Add remaining pwd options

[Rob Landley]

On 01/01/2013 06:49:00 AM, Felix Janda wrote:
> On 12/31/12 at 09:50pm, Rob Landley wrote:
> > On 12/31/2012 10:39:18 AM, Felix Janda wrote:
> > > On 12/30/12 at 05:47pm, Rob Landley wrote:
> > > > On 12/30/2012 05:16:41 AM, Felix Janda wrote:
> > > > > On 12/30/12 at 04:43am, Rob Landley wrote:
> > > > > POSIX contains many surprises. In the section on environment
> > > > > variables it
> > > > > says that $PWD should be set if "pwd -P" was specified. What
> > > happens
> > > > > if an
> > > > > error happens seems unspecified.
> > >
> > > Sorry, this is wrong. It has been changed between SUSV4 and SUSV3.
> > > Now pwd
> > > must not change $PWD. (It would be really nice to have SUSV4 man
> > > pages...)
> >
> > There are susv4 web pages which you can download and pull up with
> > "links" or similar if it really bothers you.
> 
> Having something like "man 1p pwd" is just too convenient.
> 
> > Trying to beat sane behavior out of bash is not a fruitful endeavor:
> >
> >    cd
> >    mkdir missing
> >    cd missing
> >    rmdir ../missing
> >    pwd -P
> >    cd ..
> >    ls
> >    echo $PWD
> >
> > I'm not copying that behavior.
> 
> Of course, me neither. bash seems still to try to follow the older  
> version
> of POSIX, but its version of "pwd -P" seems to be broken in another  
> way.
> 
> 
> Do I understand correctly that in the case that pwd (as a builtin of  
> toysh)
> can't determine the path of the current working directory with  
> getcwd() it
> should fall back to printing $PWD?

1) The default value is -L, and it only looks at $PWD in -L mode. If  
you say pwd -P with no cwd, it should fail.

2) If $PWD is set to a value that the shell wouldn't set it to, it's  
discarded and we fall back to -P. Specifically, if it's not an absolute  
path, or if it contains . or .. components, it is considered invalid.

3) If $PWD does not point to the current directory, fall back to -P.

What I did was disable #3 in the case where cwd doesn't exist. So the  
new rule #3 is:

3) If cwd exists and $PWD doesn't point to it, fall back to -P.

> BTW, in the case that one has deleted and recreated one's current  
> working
> directory one could also use "cd ." to get to the new directory.

Good to know. (This means the shell is special casing "." as well as  
"..". I need to read the susv4 shell stuff thoroughly, it's been  
years...)

> Felix

Rob














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