Formatting a Powershell string containing hashtable values

Question

The answer to this is likely to be trivial, but I have spent half an hour and still can't work it out.

Assume I have a the following hashtable:

$hash = @{face='Off';}

What I have tried to do, is output the value of "face" along side some other string elements.

This works:

Write-Host Face $hash['face']
=> Face Off

However, this doesn't:

Write-Host Face/$hash['face']
=> Face/System.Collections.Hashtable[face]

Somehow the lack of a space has affected the operator precedence - it is now evaluating $hash as a string, the concatenating [face] afterwards.

Trying to solve this precedence problem, I tried:

Write-Host Face/($hash['face'])
=> Face/ Off

I now have an extra space I don't want. This works, but I don't want the extra line just to reassign:

$hashvalue = $hash['face']
write-host Face/$hashvalue
=> Face/Off

Any idea how to get this working as a one-liner?

Joey · Accepted Answer · 2012-03-02 21:11:19Z

11

Sure, use a subexpression:

Write-Host Face/$($hash['face'])

Generally, I'd just use a string, if I need precise control over whitespace with Write-Host:

Write-Host "Face/$($hash['face'])"

Yes, in this case you need a subexpression again, but more because you simply can't include an expression like $foo['bar'] in a string otherwise ;-)

By the way, $hash.face works just as well with much less visual clutter.

answered Mar 2, 2012 at 21:11

Joey

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2 Comments

llevera Over a year ago

The subexpression was the key here (enclosing in $()). I was aware vaguely of their role, but had missed the applicability here.

llevera Over a year ago

Unaccepted to give others a chance to answer. Was a bit quick off the blocks

manojlds · Accepted Answer · 2012-03-02 22:04:49Z

3

In such cases, and more so if there are more variables involved, I prefer using the string formatting. While in this case you can live with the $(..), be aware that string formatting will remove lot of doubt, cruft and improves readability:

write-host ("Face/{0}" -f $hash['face'])

answered Mar 2, 2012 at 22:04

manojlds

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2 Comments

llevera Over a year ago

Thanks for pointing out the -f option. I'd never used that, and I can definitely see how it would make more complex scenarios much more manageable

Joey Over a year ago

llevera, it's an operator, not an option.

Andy Arismendi · Accepted Answer · 2012-03-02 22:08:18Z

1

In addition to using sub expressions as Joey showed you can:

Use string formatting:

Write-Host ('Face/{0}' -f $hash.face)

This will stick the value of face key in the place of {0}

Use string concatenation:

Write-Host ('Face/' + $hash.face)

Both of those require an expression to be evaluated which outputs a string which is used as Write-Host's Object parameter.

answered Mar 2, 2012 at 22:08

Andy Arismendi

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2 Comments

llevera Over a year ago

I think it is worth noting that for the Write-Host ('Face/' + $hash.face) example, the brackets are important. Without them, the + gets treated as a string literal. Powershell string formatting takes a little getting used to!

Andy Arismendi Over a year ago

@llevera Yea the parens tell PowerShell to execute the string concatenation first. The output is a System.String object which is used as the Write-Host -Object parameter value.

mjolinor · Accepted Answer · 2012-03-03 02:52:18Z

0

Another option is to insert your slash with the -Separator option of Write-Host:

$hash = @{Face="off"}
Write-Host ("Face",$hash.Face) -Separator '/'

answered Mar 3, 2012 at 2:52

mjolinor

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