How is books.xml converted to CSV and written to a file?
PS /home/nicholas/xml>
PS /home/nicholas/xml> $books = Import-Clixml books.xml
PS /home/nicholas/xml>
PS /home/nicholas/xml> $books.InnerXml
<?xml version="1.0"?><catalog><book id="bk101"><author>Gambardella, Matthew</author><title>XML Developer's Guide</title><genre>Computer</genre><price>44.95</price><publish_date>2000-10-01</publish_date><description>An in-depth look at creating applications
with XML.</description></book><book id="bk102"><author>Ralls, Kim</author><title>Midnight Rain</title><genre>Fantasy</genre><price>5.95</price><publish_date>2000-12-16</publish_date><description>A former architect battles corporate zombies,
an evil sorceress, and her own childhood to become queen
of the world.</description></book><book id="bk103"><author>Corets, Eva</author><title>Maeve Ascendant</title><genre>Fantasy</genre><price>5.95</price><publish_date>2000-11-17</publish_date><description>After the collapse of a nanotechnology
society in England, the young survivors lay the
foundation for a new society.</description></book><book id="bk104"><author>Corets, Eva</author><title>Oberon's Legacy</title><genre>Fantasy</genre><price>5.95</price><publish_date>2001-03-10</publish_date><description>In post-apocalypse England, the mysterious
agent known only as Oberon helps to create a new life
for the inhabitants of London. Sequel to Maeve
Ascendant.</description></book><book id="bk105"><author>Corets, Eva</author><title>The Sundered Grail</title><genre>Fantasy</genre><price>5.95</price><publish_date>2001-09-10</publish_date><description>The two daughters of Maeve, half-sisters,
battle one another for control of England. Sequel to
Oberon's Legacy.</description></book><book id="bk106"><author>Randall, Cynthia</author><title>Lover Birds</title><genre>Romance</genre><price>4.95</price><publish_date>2000-09-02</publish_date><description>When Carla meets Paul at an ornithology
conference, tempers fly as feathers get ruffled.</description></book><book id="bk107"><author>Thurman, Paula</author><title>Splish Splash</title><genre>Romance</genre><price>4.95</price><publish_date>2000-11-02</publish_date><description>A deep sea diver finds true love twenty
thousand leagues beneath the sea.</description></book><book id="bk108"><author>Knorr, Stefan</author><title>Creepy Crawlies</title><genre>Horror</genre><price>4.95</price><publish_date>2000-12-06</publish_date><description>An anthology of horror stories about roaches,
centipedes, scorpions and other insects.</description></book><book id="bk109"><author>Kress, Peter</author><title>Paradox Lost</title><genre>Science Fiction</genre><price>6.95</price><publish_date>2000-11-02</publish_date><description>After an inadvertant trip through a Heisenberg
Uncertainty Device, James Salway discovers the problems
of being quantum.</description></book><book id="bk110"><author>O'Brien, Tim</author><title>Microsoft .NET: The Programming Bible</title><genre>Computer</genre><price>36.95</price><publish_date>2000-12-09</publish_date><description>Microsoft's .NET initiative is explored in
detail in this deep programmer's reference.</description></book><book id="bk111"><author>O'Brien, Tim</author><title>MSXML3: A Comprehensive Guide</title><genre>Computer</genre><price>36.95</price><publish_date>2000-12-01</publish_date><description>The Microsoft MSXML3 parser is covered in
detail, with attention to XML DOM interfaces, XSLT processing,
SAX and more.</description></book><book id="bk112"><author>Galos, Mike</author><title>Visual Studio 7: A Comprehensive Guide</title><genre>Computer</genre><price>49.95</price><publish_date>2001-04-16</publish_date><description>Microsoft Visual Studio 7 is explored in depth,
looking at how Visual Basic, Visual C++, C#, and ASP+ are
integrated into a comprehensive development
environment.</description></book></catalog>
PS /home/nicholas/xml>
PS /home/nicholas/xml> $books | Export-Csv books.csv
PS /home/nicholas/xml>
PS /home/nicholas/xml> cat ./books.csv
"xml","catalog"
"version=""1.0""","System.Xml.XmlElement"
PS /home/nicholas/xml>
It would seem that $csv is converted, but how is it written as a CSV file?
Converting to JSON didn't go much better:
PS /home/nicholas/xml>
PS /home/nicholas/xml>
PS /home/nicholas/xml> $books | ConvertTo-Json
WARNING: Resulting JSON is truncated as serialization has exceeded the set depth of 2.
[
[],
[
[
"System.Xml.XmlElement",
"System.Xml.XmlElement",
"System.Xml.XmlElement",
..
even with a depth of 9 or greater.
Here's the output of $books:
PS /home/nicholas/xml>
PS /home/nicholas/xml> $books
xml catalog
--- -------
version="1.0" catalog
PS /home/nicholas/xml> $books.ChildNodes
Version : 1.0
Encoding :
Standalone :
Value : version="1.0"
InnerText : version="1.0"
Name : xml
LocalName : xml
NodeType : XmlDeclaration
PreviousSibling :
NextSibling : catalog
ParentNode : #document
ChildNodes : {}
Attributes :
OwnerDocument : #document
FirstChild :
LastChild :
HasChildNodes : False
NamespaceURI :
Prefix :
IsReadOnly : False
OuterXml : <?xml version="1.0"?>
InnerXml :
SchemaInfo : System.Xml.Schema.XmlSchemaInfo
BaseURI :
PreviousText :
book : {book, book, book, book…}
PS /home/nicholas/xml>
which is far from CSV.
Import-Clixml is not meant for importing arbitrary XML documents; it is solely designed to work with XML documents that contain CLIXML data, which is an XML-based serialization format for representing instances of .NET types for cross-process communication, such as produced by Export-Clixml. CLIXML is typically used behind the scenes in PowerShell remoting (and, more generally, cross-process communication).
Perhaps surprisingly, there is no general-purpose cmdlet for importing arbitrary XML documents (however, there is a cmdlet for querying and extracting data from XML documents, namely Select-Xml).
You have to work with the [xml] type (System.Xml.XmlDocument) to import XML data into a DOM, which then allows you to transform the data to a different format:
# Load and parse the XML file into a DOM.
($xmlDoc = [xml]::new()).Load((Convert-Path books.xml))
# Export the book child elements of the catalog element to a CSV file.
$xmlDoc.catalog.book | Export-Csv books.csv
# Parse the CSV file into objects ([pscustomobject] instances)
# and output them to the console with friendly formatting.
Import-Csv books.csv
Note: In Windows PowerShell, consider using -NoTypeInformation with Export-Csv, as well as the -Encoding parameter to control the output character encoding, which defaults to ASCII(!). In PowerShell (Core) 7+, fortunately, -NoTypeInformation is now implied and the default character encoding is (BOM-less) UTF-8.
Output:
id : bk101
author : Gambardella, Matthew
title : XML Developer's Guide
genre : Computer
price : 44.95
publish_date : 2000-10-01
description : An in-depth look at creating applications
with XML.
id : bk102
author : Ralls, Kim
title : Midnight Rain
genre : Fantasy
price : 5.95
publish_date : 2000-12-16
description : A former architect battles corporate zombies,
an evil sorceress, and her own childhood to become queen
of the world.
id : bk103
author : Corets, Eva
title : Maeve Ascendant
genre : Fantasy
price : 5.95
publish_date : 2000-11-17
description : After the collapse of a nanotechnology
society in England, the young survivors lay the
foundation for a new society.
id : bk104
author : Corets, Eva
title : Oberon's Legacy
genre : Fantasy
price : 5.95
publish_date : 2001-03-10
description : In post-apocalypse England, the mysterious
agent known only as Oberon helps to create a new life
for the inhabitants of London. Sequel to Maeve
Ascendant.
id : bk105
author : Corets, Eva
title : The Sundered Grail
genre : Fantasy
price : 5.95
publish_date : 2001-09-10
description : The two daughters of Maeve, half-sisters,
battle one another for control of England. Sequel to
Oberon's Legacy.
id : bk106
author : Randall, Cynthia
title : Lover Birds
genre : Romance
price : 4.95
publish_date : 2000-09-02
description : When Carla meets Paul at an ornithology
conference, tempers fly as feathers get ruffled.
id : bk107
author : Thurman, Paula
title : Splish Splash
genre : Romance
price : 4.95
publish_date : 2000-11-02
description : A deep sea diver finds true love twenty
thousand leagues beneath the sea.
id : bk108
author : Knorr, Stefan
title : Creepy Crawlies
genre : Horror
price : 4.95
publish_date : 2000-12-06
description : An anthology of horror stories about roaches,
centipedes, scorpions and other insects.
id : bk109
author : Kress, Peter
title : Paradox Lost
genre : Science Fiction
price : 6.95
publish_date : 2000-11-02
description : After an inadvertant trip through a Heisenberg
Uncertainty Device, James Salway discovers the problems
of being quantum.
id : bk110
author : O'Brien, Tim
title : Microsoft .NET: The Programming Bible
genre : Computer
price : 36.95
publish_date : 2000-12-09
description : Microsoft's .NET initiative is explored in
detail in this deep programmer's reference.
id : bk111
author : O'Brien, Tim
title : MSXML3: A Comprehensive Guide
genre : Computer
price : 36.95
publish_date : 2000-12-01
description : The Microsoft MSXML3 parser is covered in
detail, with attention to XML DOM interfaces, XSLT processing,
SAX and more.
id : bk112
author : Galos, Mike
title : Visual Studio 7: A Comprehensive Guide
genre : Computer
price : 49.95
publish_date : 2001-04-16
description : Microsoft Visual Studio 7 is explored in depth,
looking at how Visual Basic, Visual C++, C#, and ASP+ are
integrated into a comprehensive development
environment.