What is $pwd exactly?

I suppose it is Process Working Directory or something similar, isn't? There
are some issues that I can't explain:

*) I can change $pwd (accidentally or not), then its value is different from
both Get-Location and [environment]::CurrentDirectory.

*) I can even remove variable $pwd at all (accidentally or not) simply by
Remove-Variable pwd.

Then in both cases code that uses $pwd does not work "correctly". So, what
is $pwd exactly and how/why to use it?

--
Thanks,
Roman

The explanation - which you already know I bet <g> - is that a
readily-modified variable is not a good place to store absolute reference
information.

There's also a potential cognitive problem - one might expect that
$pwd = "Kaua'i, Hawaii"
would either set the location or return an error message; since there is no
error, we have a clear breach of contract.

I would REALLY favor exposing information as a set of properties rather than
raw variables, unless PowerShell is going to implement validation for
variables in a future version.


"Roman Kuzmin" <RomanKuzmin@discussions.microsoft.com> wrote in message
news:388D9CA6-6E24-4B7C-8233-E06240B9D57F@microsoft.com...
>I suppose it is Process Working Directory or something similar, isn't?
>There
> are some issues that I can't explain:
>
> *) I can change $pwd (accidentally or not), then its value is different
> from
> both Get-Location and [environment]::CurrentDirectory.
>
> *) I can even remove variable $pwd at all (accidentally or not) simply by
> Remove-Variable pwd.
>
> Then in both cases code that uses $pwd does not work "correctly". So, what
> is $pwd exactly and how/why to use it?
>
> --
> Thanks,
> Roman

My understanding is that $pwd is the PowerShell Working Directory which
is different then the working directory of the normal Windows command
shell. The reason for having two different "working directories" is
that the working directory in PowerShell can be more than just a folder
on the hard drive. For example, registry hives are mapped to "drives"
so you could use folder navigation semantics to navigate the registry.
If you did "set-location hklm:\" in PowerShell that's works just fine,
but only the PowerShell will know how to handle that as the current
folder.

On Dec 12, 5:15 am, Roman Kuzmin
<RomanKuz...@discussions.microsoft.com> wrote:
> So, what is $pwd exactly and how/why to use it?

That wasn't what he was getting at. It's the fact that $pwd is unprotected,
making it something to avoid in code. Another demo:

PS> set-location c:\temp
PS> remove-variable pwd
PS> "$pwd\script.config"
\script.config
PS> $pwd = "c:\windows\system32"
PS> "$pwd\script.config"
c:\windows\system32\script.config
PS> Get-Location

Path
----
C:\temp


<rhy@rhy.com> wrote in message
news:1165945295.409172.102980@79g2000cws.googlegroups.com...
> My understanding is that $pwd is the PowerShell Working Directory which
> is different then the working directory of the normal Windows command
> shell. The reason for having two different "working directories" is
> that the working directory in PowerShell can be more than just a folder
> on the hard drive. For example, registry hives are mapped to "drives"
> so you could use folder navigation semantics to navigate the registry.
> If you did "set-location hklm:\" in PowerShell that's works just fine,
> but only the PowerShell will know how to handle that as the current
> folder.
>
> On Dec 12, 5:15 am, Roman Kuzmin
> <RomanKuz...@discussions.microsoft.com> wrote:
>> So, what is $pwd exactly and how/why to use it?
>

In Unix PWD = Print Working Directory

$pwd is a variable that does essentially the same thing. It contains the
PathInfo object for the current location.

PS>$pwd

Path
----
C:\WINDOWS\system32\WindowsPowerShell\v1.0


PS>cd ..
PS>$pwd

Path
----
C:\WINDOWS\system32\WindowsPowerShell


PS>cd HKLM:\Software
PS>pwd

Path
----
HKLM:\Software


PS>$pwd | gm


TypeName: System.Management.Automation.PathInfo

Name MemberType Definition
---- ---------- ----------
Equals Method System.Boolean Equals(Object obj)
GetHashCode Method System.Int32 GetHashCode()
GetType Method System.Type GetType()
get_Drive Method System.Management.Automation.PSDriveInfo
get_Dri...
get_Path Method System.String get_Path()
get_Provider Method System.Management.Automation.ProviderInfo
get_Pr...
get_ProviderPath Method System.String get_ProviderPath()
ToString Method System.String ToString()
Drive Property System.Management.Automation.PSDriveInfo Drive
{...
Path Property System.String Path {get;}
Provider Property System.Management.Automation.ProviderInfo
Provid...
ProviderPath Property System.String ProviderPath {get;}


PS>


"Alex K. Angelopoulos [MVP]" <aka@online.mvps.org> wrote in message
news:eThZsyhHHHA.1280@TK2MSFTNGP04.phx.gbl...
> That wasn't what he was getting at. It's the fact that $pwd is
> unprotected, making it something to avoid in code. Another demo:
>
> PS> set-location c:\temp
> PS> remove-variable pwd
> PS> "$pwd\script.config"
> \script.config
> PS> $pwd = "c:\windows\system32"
> PS> "$pwd\script.config"
> c:\windows\system32\script.config
> PS> Get-Location
>
> Path
> ----
> C:\temp
>
>
> <rhy@rhy.com> wrote in message
> news:1165945295.409172.102980@79g2000cws.googlegroups.com...
>> My understanding is that $pwd is the PowerShell Working Directory which
>> is different then the working directory of the normal Windows command
>> shell. The reason for having two different "working directories" is
>> that the working directory in PowerShell can be more than just a folder
>> on the hard drive. For example, registry hives are mapped to "drives"
>> so you could use folder navigation semantics to navigate the registry.
>> If you did "set-location hklm:\" in PowerShell that's works just fine,
>> but only the PowerShell will know how to handle that as the current
>> folder.
>>
>> On Dec 12, 5:15 am, Roman Kuzmin
>> <RomanKuz...@discussions.microsoft.com> wrote:
>>> So, what is $pwd exactly and how/why to use it?
>>
>
>

Hi Marcel,

> In Unix PWD = Print Working Directory
>
> $pwd is a variable that does essentially the same thing. It contains the
> PathInfo object for the current location.

But why introducing a fragile variable named $pwd if there's already an
alias pwd that does essentially the same?

cu

Max

"Alex K. Angelopoulos [MVP]" <aka@online.mvps.org> wrote
> That wasn't what he was getting at. It's the fact that $pwd is
> unprotected, making it something to avoid in code.

Yes, exactly. I did have a real problem with using $pwd and asked this
question already having bad experience. From now on I do not use $pwd in my
code.

--
Thanks,
Roman

"Roman Kuzmin" <z@z.z> wrote in message
news:ev9GpUqHHHA.1188@TK2MSFTNGP06.phx.gbl...
> "Alex K. Angelopoulos [MVP]" <aka@online.mvps.org> wrote
>> That wasn't what he was getting at. It's the fact that $pwd is
>> unprotected, making it something to avoid in code.
>
> Yes, exactly. I did have a real problem with using $pwd and asked this
> question already having bad experience. From now on I do not use $pwd in
> my code.

Further notes.

+ Unix
This appears to be a ksh shell variable on Unix; see this page:
http://node1.yo-linux.com/cgi-bin/ma...gi_command=ksh
under the Parameters section.

I don't have ksh on my system right now to test reliability, but here's what
the man page says:
PWD: The current working directory. Maybe unset or null if shell doesn't
know where it is.
So there clearly CAN be problems.

+ cmd.exe
%CD% has the same issue, only more so. If you do this:
set CD=foo
then CD is foo no matter how many times you change directories until you do
set CD=
followed by a location change.


Personally, I think it might be a good idea to make $pwd read-only. This
would still allow forcing overwrite if you really, really, really want to
fake it for some reason.

"Maximilian Hänel" <ngSpam@smjh.de> wrote in message
news:uEnWnqjHHHA.5104@TK2MSFTNGP03.phx.gbl...
> Hi Marcel,
>
>> In Unix PWD = Print Working Directory
>>
>> $pwd is a variable that does essentially the same thing. It contains the
>> PathInfo object for the current location.
>
> But why introducing a fragile variable named $pwd if there's already an
> alias pwd that does essentially the same?

I suspect it's because an alias executes whereas a variable doesn't (i.e.
perhaps it gets updated statically as the Shell is used); the alias may be
(or might be perceived to be) treated differently in more complex scripts
that need to reference the $pwd as a string.

Then again, I may be (or might be perceived to be) talking with hot air
derived from my gut feelings and eminating from my backside.

Jon