Why is the precedence for the property operator not being honored

In the below statement Powershell I think should be binding the $_ to
DeviceID and then evaluating the variable. What its doing is expanding the $_
and concatenating the .DeviceID.

Is the current behavior what is expected?

Get-WmiObject Win32_logicaldisk | % {if ($_.DriveType -eq 3) {"The amount of
free space on drive $_.DeviceID is $_.FreeSpace"}}



thx
bob

Try this... you have to put $( ) around Variables to let them expand.

Get-WmiObject Win32_logicaldisk | % {if ($_.DriveType -eq 3) {"The amount of
free space on drive $($_.DeviceID) is $($_.FreeSpace)"}}

"Bob Landau" <BobLandau@xxxxxx> wrote in message
news:8B55372C-692B-4C35-BA1D-664BE3BD3B06@xxxxxx

Oh... another option
Get-WmiObject Win32_logicaldisk | % {if ($_.DriveType -eq 3){"The amount of
free space on drive {0} is {1}" -f ($_.DeviceID),($_.FreeSpace)}}

More Info about the -f operator here
http://bsonposh.com/modules/wordpress/?p=35

"Bob Landau" <BobLandau@xxxxxx> wrote in message
news:8B55372C-692B-4C35-BA1D-664BE3BD3B06@xxxxxx

"Brandon Shell" <tshell.mask@xxxxxx> wrote in message
news:eoDTQkj8HHA.4880@xxxxxx The thing to keep in mind here is double-quoted strings in PowerShell will
do variable expansion i.e. $_ is expanded to the string representation of a
Win32_LogicalDisk instance:

\\KEITH1\root\cimv2:Win32_LogicalDisk.DeviceID="C:"

However double-quoted string expansion doesn't support evaluating an
expression by default, which is what accessing properties of a variable
would require. You probably wouldn't want this anyway otherwise something
like this:

"The date is $date."

would error because there is a property operator (.) after the $date object
but you specified no property. So as Brandon points out, the $() in a
string allows you evaluate one or more expressions within the string and the
results are converted to their string representations and placed into the
string.

BTW it is pretty easy to get tripped up on this. I used to do it a lot in
my scripts. I think I'm finally getting to the point where I don't make
this mistake very often.

--
Keith

Thank you Brandon,

I like both of your ideas. But I still don't understand whether the current
behavior is expected or not. It seems a shame to need to require anything
special simply to get the value of a property.

Both the QuickStart wiki and "Windows Powershell in Action" both state the
member operator is high up on the order of precedence.


"Brandon Shell" wrote:

Keith just explained it well... it is expected.

"Bob Landau" <BobLandau@xxxxxx> wrote in message
news:E5AE901A-EADF-4EF6-B815-21992E492DFA@xxxxxx

Thanks,

I of course hadn't thought about the even more common usage you described
below.

bob


"Keith Hill" wrote:

Alternatively you could concatenate the string:

Get-WmiObject Win32_logicaldisk | % {if ($_.DriveType -eq 3) {"The amount of
free space on drive " + $_.DeviceID + " is " + $_.FreeSpace}}

--
Kiron

Some more examples...

# When -format operator is used you can remove the braces on ($_.property)
Get-WmiObject Win32_logicaldisk | foreach {if ($_.DriveType -eq 3){"The amount
of free space on drive {0} is {1}" -f $_.DeviceID,$_.FreeSpace}}

#narrow down returned properties using the where clause (aka server side
processing)
Get-WmiObject -query "select DeviceID,FreeSpace from Win32_logicaldisk where
DriveType = 3" | foreach {"Free space on drive {0} is {1}" -f $_.DeviceID,$_.FreeSpace}

#narrow down returned properties using the -filter parameter (server side
processing)
Get-WmiObject -class Win32_logicaldisk -filter "DriveType = 3" | foreach
{"Free space on drive {0} is {1}" -f $_.DeviceID,$_.FreeSpace}


Shay
http://scriptolog.blogspot.com