Edit Single Line XML File In PowerShell Without Changing to Multi-Line XML File

I have a HUGE XML file that has a whole ton of data packed into a single line. I've found when I edit that file with PowerShell, it breaks all of the data up into individual lines instead of a single line. Initially it was changing the encoding from UTF-8 to UTF-8 BOM so I thought that might be the culprit. I've since fixed that portion of my script and made sure it's still saving as UTF-8 without BOM, but everything is still getting converted from one line to over 600 lines after I run my script.

Anyone know any tricks to keep the formatting on single line xml files when editing in PowerShell?

Solution

Assuming that your XML file still fits into memory as an [xml] (System.Xml.XmlDocument) DOM:

When you pass a file path to the .Save() method, pretty-printing of the XML is performed by default.
To modify this default behavior you must construct a System.Xml.XmlWriter instance based on a custom System.Xml.XmlWriterSettings instance that gives you control over the serialization behavior.
- In fact, such settings default to not pretty-print, and would require setting the .Indent property to $true for pretty-printing.
- You can also use the .Encoding property in order to specify a BOM-less UTF-8 encoding, as is your intent.

Here's a self-contained example:

# Sample input XML
[xml] $xml = '<?xml version="1.0"?><catalog><book id="bk101"><title>De Profundis</title></book></catalog>'

# Create a non-pretty-printing XmlWriter instance 
# with BOM-less UTF-8 encoding that will write to file "test.xml"
# in the current directory.
$writer = [System.Xml.XmlWriter]::Create(
  "$PWD/test.xml", # IMPORTANT: Use a FULL PATH here, because .NET's working dir. usually differs from PowerShell's
  [System.Xml.XmlWriterSettings] @{ Encoding = [Text.UTF8Encoding]::new() }
)

try {
  # Save the document via the writer.
  $xml.Save($writer)
} finally {
  # (Close and) dispose of the writer.
  $writer.Dispose()
}