How do I concatenate strings and variables in PowerShell?

Suppose I have the following snippet:

$assoc = New-Object PSObject -Property @{
    Id = 42
    Name = "Slim Shady"
    Owner = "Eminem"
}

Write-Host $assoc.Id + "  -  "  + $assoc.Name + "  -  " + $assoc.Owner

I'd expect this snippet to show:

42 - Slim Shady - Eminem

But instead it shows:

42 + - + Slim Shady + - + Eminem

Which makes me think the + operator isn't appropriate for concatenating strings and variables.

How should you approach this with PowerShell?

Write-Host "$($assoc.Id) - $($assoc.Name) - $($assoc.Owner)"

See the Windows PowerShell Language Specification Version 3.0, p34, sub-expressions expansion.

There is a difference between single and double quotes. (I am using PowerShell 4).

You can do this:

$name = 'Slim Shady'
Write-Host 'My name is'$name
-> My name is Slim Shady

Or you can do this:

$name = 'Slim Shady'
Write-Host "My name is $name"
-> My name is Slim Shady

The single quotes are for literal, output the string exactly like this, please. The double quotes are for when you want some pre-processing done (such as variables, special characters, etc.)

So:

$name = "Marshall Bruce Mathers III"
Write-Host "$name"
-> Marshall Bruce Mathers III

Whereas:

$name = "Marshall Bruce Mathers III"
Write-Host '$name'
-> $name

(I find How-to: Escape characters, Delimiters and Quotes good for reference).

You can also use -join

E.g.

$var = -join("Hello", " ", "world");

Would assign "Hello world" to $var.

So to output, in one line:

Write-Host (-join("Hello", " ", "world"))

One way is:

Write-Host "$($assoc.Id)  -  $($assoc.Name)  -  $($assoc.Owner)"

Another one is:

Write-Host  ("{0}  -  {1}  -  {2}" -f $assoc.Id,$assoc.Name,$assoc.Owner )

Or just (but I don't like it ;) ):

Write-Host $assoc.Id  "  -  "   $assoc.Name  "  -  "  $assoc.Owner

Try wrapping whatever you want to print out in parentheses:

Write-Host ($assoc.Id + "  -  "  + $assoc.Name + "  -  " + $assoc.Owner)

Your code is being interpreted as many parameters being passed to Write-Host. Wrapping it up inside parentheses will concatenate the values and then pass the resulting value as a single parameter.

Another option is:

$string = $assoc.ID
$string += " - "
$string += $assoc.Name
$string += " - "
$string += $assoc.Owner
Write-Host $string

While expression:

"string1" + "string2" + "string3"
will concatenate the string, you need to put a $ in front of the parenthesis to make it evaluate as a single argument when passed to a PowerShell command. Example:

Write-Host $( "string1" + "string2" + "string3" )
As a bonus, if you want it to span multiple lines, then you need to use the awkward backtick syntax at the end of the line (without any spaces or characters to the right of the backtick).

Example:

Write-Host $( "The rain in " +
"Spain falls mainly " + "in the plains" )
-ForegroundColor Yellow
(Actually, I think PowerShell is currently implemented a little bit wrong by requiring unnecessary backticks between parentheses. If Microsoft would just follow Python or Tcl parenthesis rules of allowing you to put as many newlines as you want between the starting and ending parenthesis then they would solve most of the problems that people don't like about PowerShell related to line continuation, and concatenation of strings.

I've found that you can leave the backticks off sometimes on line continuations between parenthesis, but it's really flaky and unpredictable if it will work... It's better to just add the backticks.)