Vista - trapping oddity

where we run:

function a
{
trap { write-host ("trapped " + $_.Exception.GetType().Name); continue;
}
write-host "starting b"
write-host ($(1 / $null))
write-host "ending b"
}

a

despite the exception being trapped and shown as trapped, the ending b
is written. i think it shouldn't do that..

however

function a
{
trap { write-host ("trapped " + $_.Exception.GetType().Name); continue;
}

}

function b
{
write-host "starting b"
write-host ($(1 / $null))
write-host "ending b"

}

a

runs as expected (it doesn't print the "ending b"

Karl

Just to check: I think that you meant to write the second a function as:

function a
{
trap { write-host ("trapped " + $_.Exception.GetType().Name); continue; }
b # - this was missing...
}

Anyway, traps are scoped to the statement block containing the trap. On an
exception, trap/continue transfers control to the next statement in *that*
block. So - if the exception occurs in a function call, the rest of that
function will be skipped and control will continue at the next statement
after where the function was called. There is a very useful pattern that
takes advantage of this:

PS (1) > & {
>> trap { "Got error" ; continue }
>> . {
>> "first"
>> "second"
>> 1/$null
>> "third"
>> "fourth"
>> }
>> "Finally"
>> }
>>
first
second
Got error
Finally
PS (2) >


By using the scriptblock to scope a set of statements, you can skip to the
end of the set instead of having to write a bunch of conditionals. This is
the effective equivalent to

try {
"first"
"second"
1/$null
"third"
}
catch {
"Got error"
}
finally {
"Finally"
}

-bruce

--
Bruce Payette [MSFT]
Windows PowerShell Technical Lead
Microsoft Corporation
This posting is provided "AS IS" with no warranties, and confers no rights.



<klumsy@xtra.co.nz> wrote in message
news:1159545338.913882.81790@h48g2000cwc.googlegroups.com...
> where we run:
>
> function a
> {
> trap { write-host ("trapped " + $_.Exception.GetType().Name); continue;
> }
> write-host "starting b"
> write-host ($(1 / $null))
> write-host "ending b"
> }
>
> a
>
> despite the exception being trapped and shown as trapped, the ending b
> is written. i think it shouldn't do that..
>
> however
>
> function a
> {
> trap { write-host ("trapped " + $_.Exception.GetType().Name); continue;
> }
>
> }
>
> function b
> {
> write-host "starting b"
> write-host ($(1 / $null))
> write-host "ending b"
>
> }
>
> a
>
> runs as expected (it doesn't print the "ending b"
>
> Karl
>

thanks bruce, that was good info..
yep i typed in the example wrong.. my bad