Passing a "string" variable in powershell through a pipe (|) doesn't work

Question

Can't think any way but with ksh/perl, so powershell is annoying.

Attempting to process through a list of names and execute a command in which the variable is combined/concatenated with another string.

Input:

PS C:\WINDOWS\SysWOW64\windowspowershell\v1.0> $fc_volumes | select-object -first 10

    volume
    ------ 
    dnvlxd531_archives 
    dnvux100_quorum 
    oraapps_quorum 
    dnv05_lun04 
    sdw_cl_dnv05_lun11_0 
    FCP_vol132 
    dnv05_lun37 
    dnv05_lun36

Attempted command and output:

PS C:\WINDOWS\SysWOW64\windowspowershell\v1.0> $fc_volumes | foreach-object { $_ } {dfm perf data retrieve -o dnvnaf005:/$_ -C volume:total_ops -V "Volume IOPs View" }
Error: Failed to get counter data
        Reason: There is no object named 'dnvnaf005:/Microsoft.PowerShell.Commands.Internal.Format.FormatStartData'.
Error: Failed to get counter data
        Reason: There is no object named 'dnvnaf005:/Microsoft.PowerShell.Commands.Internal.Format.GroupStartData'.
Error: Failed to get counter data
        Reason: There is no object named 'dnvnaf005:/Microsoft.PowerShell.Commands.Internal.Format.FormatEntryData'.
Error: Failed to get counter data
        Reason: There is no object named 'dnvnaf005:/Microsoft.PowerShell.Commands.Internal.Format.FormatEntryData'.
Error: Failed to get counter data

The parser is obviously seeing the formatted stream, but I can't seem to figure out how to have it use just the value, and not all the formating.

Thanks,

Mike

zdan · Accepted Answer · 2011-11-16 23:04:10Z

5

$fc_volumes doesn't seem to contain strings but a group of objects with a "volume" property. You can use the Select-Object cmdlet to expand this property on the pipeline to just give you the strings:

$fc_volumes | select-object -ExpandProperty "volume" | foreach-object {dfm perf data retrieve -o dnvnaf005:/$_ -C volume:total_ops -V "Volume IOPs View" }

or you could just do it inline in your foreach loop by accessing the property directly:

$fc_volumes | foreach-object {dfm perf data retrieve -o dnvnaf005:/$_.volume -C volume:total_ops -V "Volume IOPs View" }

edited Nov 16, 2011 at 23:04

answered Nov 14, 2011 at 23:47

zdan

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Andrew Savinykh · Accepted Answer · 2011-11-16 04:55:36Z

2

In addition to zdan's answer, which is spot on, I'd like to point out that you should only use format-* cmdlets at the very end of the pipeline as they are intended to formar output to console. There is no use in iterating through format-* results. Those Microsoft.PowerShell.Commands.Internal.Format.* you are getting - they are the wrapped strings with attached format information to it, you do not need those. Refactor you code so that you only invoke Format-* on whatever is displayed to the user and if you pass some results for futher processing (like for getting performance counters) this should be done before these were formated with Format-*

answered Nov 16, 2011 at 4:55

Andrew Savinykh

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