Use variables in string replace - Windows powershell

Question

I have a requirement where my string is of format as below:

<?define BuildNumber = "8314" ?>

I am using below powershell script in TFS 2017 build template to replace the build number value:

$content = Get-Content -path "$(Build.SourcesDirectory)\Install\Common\Constants.wxi"
$num  = $(Build.BuildId)
$content -Replace '(BuildNumber\s*=\s*")\d*("\s*)', "`$1 $num `$2" |  Out-File $(Build.SourcesDirectory)\Install\Common\Constants.wxi

This gives output like <?define BuildNumber = " 27994 " ?> which is incorrect as I do not want spaces in the value. When I tried using below code, it does not work.

$content -Replace '(BuildNumber\s*=\s*")\d*("\s*)', "`$1$num`$2" |  Out-File  $(Build.SourcesDirectory)\Install\Common\Constants.wxi

Output : <?define $27994 ?>

I tried all combinations but cannot get the quotations to work correctly. Please suggest a solution.

Possible duplicate of Why is powershell -replace operator not properly including all characters captured in the capture group? — user4003407
– user4003407, Commented Dec 13, 2018 at 10:47
@Olaf This is a solution. I was actually not able to understand why it was not working in the original code. — Mustafa
– Mustafa, Commented Dec 13, 2018 at 11:30

montonero · Accepted Answer · 2018-12-13 13:26:30Z

2

Use curly braces to "escape" group number

$content -Replace '(BuildNumber\s*=\s*")\d*("\s*)', "`${1}$num`$2" | Out-File $(Build.SourcesDirectory)\Install\Common\Constants.wxi

A little clarification about why the original code doesn't work: after $num variable has been resolved the replace string became $127994$2. That means that the -replace operator is trying to find group $127994 which obviously does not exist. When we add curly braces it becomes ${1}27994$2 which is completely legit.

edited Dec 13, 2018 at 13:26

answered Dec 13, 2018 at 11:00

montonero

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2 Comments

Mustafa Over a year ago

Thanks for the quick reply. Worked like magic. I am a little new to powershell scripting.

montonero Over a year ago

@Mustafa I've added a clarification about why your code doesn't worked as expected.

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