Is there a string concatenation shortcut in PowerShell? - powershell

Question

Like with numerics?
For example,
$string = "Hello"
$string =+ " there"
In Perl you can do
my $string = "hello"
$string .= " there"
It seems a bit verbose to have to do
$string = $string + " there"
or
$string = "$string there"

Answer 1

You actually have the operator backwards. It should be +=, not =+:
$string = "Hello"
$string += " there"
Below is a demonstration:
PS > $string = "Hello"
PS > $string
Hello
PS > $string += " there"
PS > $string
Hello there
PS >
However, that is about the quickest/shortest solution you can get to do what you want.

Answer 2

Avoid += for building strings
As for using the increase assignment operator (+=) to create a collection, strings are also mutual, therefore using the increase assignment operator (+=) to build a string might become pretty expensive as it will concatenate the strings and assign (copy!) it back into the variable. Instead I recommend to use the PowerShell pipeline with the -Join operator to build your string.
Apart from the fact it is faster it is actually more DRY as well:
$String = 'Hello', 'there' -Join ' ' # Assigns: 'Hello there'
Or just
-Join #('One', 'Two', 'Three') # Yields: 'OneTwoThree'
For just a few items it might not make much sense but let me give you a a more common example by creating a formatted list of numbers, something like:
[Begin]
000001
000002
000003
[End]
You could do this:
$x = 3
$String = '[Begin]' + [Environment]::NewLine
for ($i = 1; $i -le $x; $i++) { $String += '{0:000000}' -f $i + [Environment]::NewLine }
$String += '[End]' + [Environment]::NewLine
But instead, you might actually do it the PowerShell way:
$x = 3
$String = #(
'[Begin]'
for ($i = 1; $i -le $x; $i++) { '{0:000000}' -f $i }
'[End]'
) -Join [Environment]::NewLine
Performance Testing
To show the performance decrease of using the increase assignment operator (+=), let's increase $x with a factor 1000 up till 20.000:
1..20 | ForEach-Object {
$x = 1000 * $_
$Performance = #{x = $x}
$Performance.Pipeline = (Measure-Command {
$String1 = #(
'[Begin]'
for ($i = 1; $i -le $x; $i++) { '{0:000000}' -f $i }
'[End]'
) -Join [Environment]::NewLine
}).Ticks
$Performance.Increase = (Measure-Command {
$String2 = '[Begin]' + [Environment]::NewLine
for ($i = 1; $i -le $x; $i++) { $String2 += '{0:000000}' -f $i + [Environment]::NewLine }
$String2 += '[End]' + [Environment]::NewLine
}).Ticks
[pscustomobject]$Performance
} | Format-Table x, Increase, Pipeline, #{n='Factor'; e={$_.Increase / $_.Pipeline}; f='0.00'} -AutoSize
Results:
x Increase Pipeline Factor
- -------- -------- ------
1000 261337 252704 1,03
2000 163596 63225 2,59
3000 432524 127788 3,38
4000 365581 137370 2,66
5000 586370 171085 3,43
6000 1219523 248489 4,91
7000 2174218 295355 7,36
8000 3148111 323416 9,73
9000 4490204 373671 12,02
10000 6181179 414298 14,92
11000 7562741 447367 16,91
12000 9721252 486606 19,98
13000 12137321 551236 22,02
14000 14042550 598368 23,47
15000 16390805 603128 27,18
16000 18884729 636184 29,68
17000 21508541 708300 30,37
18000 24157521 893584 27,03
19000 27209069 766923 35,48
20000 29405984 814260 36,11
See also: PowerShell scripting performance considerations - String addition