PowerShell: -replace, regex and ($) dollar sign woes

Question

I am in the process of converting thousands of lines of batch code into PowerShell. I'm using regex to help with this process. The problem is part of the code is:

$`$2

When replaced it just shows $2 and doesn't expand out the variable. I've also used single quotes for the second portion of replace instead of escaping the variables, same result.

$origString = @'
IF /I "%OPERATINGSYSTEM:~0,6%"=="WIN864" SET CACHE_OS=WIN864
...many more lines of batch code
'@

$replacedString = $origString -replace "(IF /I `"%)(.+)(:.+%`"==`")(.+`")(.+)","if ( $`$2 -match `"^`$4 ) {`$5 }"

$replacedString

Just for completeness sake whenever you post a string manipulation question, It would help everyone if you could give an example of the text before the manipulation (which you have) and what the string should look like after the manipulation. — EBGreen

stej stej · Accepted Answer · 2012-02-22T19:48:58

You could try something like this:

$origString -replace "(IF /I `"%)(.+)(:.+%`"==`")(.+`")(.+)",'if ($$$2 -match "^$4" ) {$5 }'

Note the $$$2. This evaluates to $ and content of $2.

Some code to show you the differences. Try it yourself:

'abc' -replace 'a(\w)', '$1'
'abc' -replace 'a(\w)', "$1"  # "$1" is expanded before replace to ''
'abc' -replace 'a(\w)', '$$$1'
'abc' -replace 'a(\w)', "$$$1" #variable $$ and $1 is expanded before regex replace
                               #$$ and $1 don't exist, so they are expanded to ''

$$ = 'xyz'
$1 = '123'
'abc' -replace 'a(\w)', "$$$1`$1" #"$$$1" is expanded to 'xyz123', but `$1 is used in regex

PowerShell: -replace, regex and ($) dollar sign woes

2 Answers