Replace text between two string powershell

Question

I have a question which im pretty much stuck on..

I have a file called xml_data.txt and another file called entry.txt

I want to replace everything between <core:topics> and </core:topics>

I have written the below script

$test = Get-Content -Path ./xml_data.txt
$newtest = Get-Content -Path ./entry.txt
$pattern = "<core:topics>(.*?)</core:topics>"
$result0 = [regex]::match($test, $pattern).Groups[1].Value
$result1 = [regex]::match($newtest, $pattern).Groups[1].Value
$test -replace $result0, $result1

When I run the script it outputs onto the console it doesnt look like it made any change.

Can someone please help me out

Note: Typo error fixed

Use `$test = Get-Content -Path ./xml_data.txt -Raw`, and `$pattern = "(?s)(.*?)"` — Wiktor Stribiżew, Aug 20 '19 at 11:25
[DO NOT parse XML with regex](http://stackoverflow.com/a/1732454/1630171). For manipulating XML data use PowerShell's builtin XML parser. Beware that your data apparently is using [namespaces](https://stackoverflow.com/a/35653697/1630171), so you need to take care of that. — Ansgar Wiechers, Aug 20 '19 at 11:26
@WiktorStribiżew What if I have mutiple entry how will i loop that — Sabbir Ahmed, Aug 20 '19 at 12:48
Sorry, I think your question is rather unclea and a bit too broad. — Wiktor Stribiżew, Aug 20 '19 at 14:10
@WiktorStribiżew Dont Worry, i got it working! your first solution did the trick thank you :) — Sabbir Ahmed, Aug 22 '19 at 15:34

score 3 · Accepted Answer · answered Aug 22 '19 at 16:16

There are three main issues here:

You read the file line by line, but the blocks of texts are multiline strings
Your regex does not match newlines as . does not match a newline by default
Also, the literal regex pattern must when replacing with a dynamic replacement pattern, you must always dollar-escape the $ symbol. Or use simple string .Replace.

So, you need to

Read the whole file in to a single variable, $test = Get-Content -Path ./xml_data.txt -Raw
Use the $pattern = "(?s)<core:topics>(.*?)</core:topics>" regex (it can be enhanced in case it works too slow by unrolling it to <core:topics>([^<]*(?:<(?!</?core:topics>).*)*)</core:topics>)
Use $test -replace [regex]::Escape($result0), $result1.Replace('$', '$$') to "protect" $ chars in the replacement, or $test.Replace($result0, $result1).

Replace text between two string powershell

1 Answers1