Prof. Powershell

Here, Here (The Here String)

Order in the script -- with the here string.

• By Jeffery Hicks
• 02/14/2012

Have you ever found yourself trying to do something like this?

PS C:\> $p="Menu 'nSelect a task 'n 1 Get running services 'n 2 Get processes '
n 3 Get recent system errors"
PS C:\> Read-host $p
Menu
Select a task
 1 Get running services
 2 Get processes
 3 Get recent system errors: _

It kinda, sorta works but I think it's a real pain to construct, especially trying to get the new lines just right. A better approach is to use a here string. This is a great technique for creating a multiline string. Here is an example:

PS C:\> $h=@"
>> I am
>> the second line
>> the third line
>> the last line
>> "@
>>

The variable $h is a string:

PS C:\> $h.gettype().name
String

But it retains the line returns:

PS C:\> $h
I am
the second line
the third line
the last line

One thing to be aware of when creating here strings in a script: The command must not be indented at all. If you use the ISE you'll see a properly defined here string in dark red. But now it is much easier to do something like this:

#define a prompt
$p=@"
\\\\\\\\
  Menu
////////

  1 - Get Running Services
  2 - Get Processes
  3 - Get Recent System Errors

Please select a task
"@
$r=read-host $p

Switch ($r) {

1 {Get-service | where {$_.status -eq "Running"} }
2 {Get-process}
3 {Get-eventlog system -EntryType Error -Newest 5}
Default {Write-Host "Invalid choice: $r" -fore Yellow}

}

If I run a script with this, here's the output:

\\\\\\\\
  Menu
////////

  1 - Get Running Services
  2 - Get Processes
  3 - Get Recent System Errors

Please select a task: 3

  Index Time         EntryType Source               InstanceID Message
  ----- ----         --------- ------               ---------- -------
1513191 Jan 31 21:16 Error     Microsoft-Windows...         12 The pla...
1513189 Jan 31 23:42 Error     SCardSvr                    616 The des...
1513188 Jan 31 23:42 Error     SCardSvr                    612 The des...
1513187 Jan 31 23:42 Error     SCardSvr                    610 The des...
1513186 Jan 31 23:42 Error     SCardSvr                    610 The des...

The here string provides a much easier way to construct a formatted multiline string. And because it is still a string, normal quoting rules apply:

PS C:\> $h=@"
>> User=$env:username
>>   Process Count=$((get-process).Count)
>>   OS=$((Get-WmiObject win32_operatingsystem).Caption)
>> "@
>>
PS C:\> $h
User=Jeff
  Process Count=131
  OS=Microsoft Windows 7 Ultimate

So the next time you need a complex string, don't trip over a bunch of escape characters and concatenation, start here.