Parsing Markdown formatted text into BBCode With Powershell

Question

I am trying to write a Markdown to BBCode parser. In this example the markdown input is:

This is **bold** but this is also **bold**.
This too is **bold** but and so is this**bold**.

And the BBCode output I am trying to program is:

This is [b]bold[/b] but this is also [b]bold[/b].
This too is [b]bold[/b] but and so is this[b]bold[/b].

My code PowerShell:

$MarkdownString ={This is **bold** but this is also **bold**.
This too is **bold** but and so is this**bold**.}

I removed the ** and replaced it with [b]:

$MarkdownString -Replace '\*\*', '[b]' | New-Variable - BBCodeOutput1

And then trying to fix the lack of a \ in the closing tag for BBCode [\B]

$BBCodeOutput1 -replace '\[b\].*?\[b\]', '\[b\].*?\[\\b\]' | New-Variable -BBCodeOutput2

But the replace Operator second parameter field just interprets everything to be literal text and not Regular expression.

I am sooo confused now, the docs say -Replace is fully RegEx capable while Replace() is not.

PS: Any ideas on how to handle this this task would be so welcome!!

To add to zett42's helpful answer: a concise summary of the features of the `-replace` operator, notably also with respect to the placeholders you can use in the replacement operand, can be found in [this answer](https://stackoverflow.com/a/40683667/45375). — mklement0, Jul 24 '22 at 22:21

zett42 · Accepted Answer · 2022-07-24T20:35:39.437

This can be done using a single -replace operation with a capture group:

$MarkdownString = @'
This is **bold** but this is also **bold**.
This too is **bold** but and so is this**bold**.
'@

$MarkdownString -replace '\*\*(.+?)\*\*', '[b]$1[/b]'

Output:

This is [b]bold[/b] but this is also [b]bold[/b].
This too is [b]bold[/b] but and so is this[b]bold[/b].

Explanation:

(...) defines a capture group. Its captured value (the sub string between two occurences of **) is then referred to in the substitute using the placeholder $1 which stands for the 1st capture group.

See regex101 demo for detailed explanation and the ability to play around with the RegEx.

Notes:

PowerShell 7+ contains a ConvertFrom-Markdown command which could be the basis for a more robust Markdown-to-BBCode converter.
If you need something even more powerful, there are also Markdown parsers for .NET which could be used from PowerShell as well. E. g. markdig.

What a pretty example, I was looking for something like `$1` placeholder so badly I just gave it up on it. Thanks allot for this example. I am gonna expremiment with it allot. As for your suggestion, I am mostly using these implementations as an excuse to learn programming in Powershell but I will take a look at your links for sure. Thanks! — hellen_dorandt89, Jul 24 '22 at 22:02

Parsing Markdown formatted text into BBCode With Powershell

1 Answers1