How can I use ForEach-Object output for Select-String directly?

Question

I have several single line xml files out of which I want to extract the contents of a particular tag <LIFNR>. I managed doing that using the following two lines of power shell:

get-content P:\Webservice\21*_*CR_d*.xml | foreach-object { $_ -replace '>', ">`r`n" } > xmls_newline.txt
get-content .\xmls_newline.txt | Select-String -Pattern '.*<\/LIFNR>'

However if I want to skip the step of creating an intermediary text file I cannot achieve the same result.

$xml = get-content P:\Webservice\21*_*CR_d*.xml | foreach-object { $_ -replace '>', ">`r`n" }
$xml | Select-String -Pattern '.*<\/LIFNR>'

or

get-content P:\Webservice\21*_*CR_d*.xml | foreach-object { $_ -replace '>', ">`r`n" } | Select-String -Pattern '.*<\/LIFNR>'

each just print the result of the string splitting in the foreach-object statement, the Select-String command is ignored.

Can somebody explain to me what is different about the latter two attempts compared to the working solution?

A valid concern, but for one thing I don't know how and - more importantly - I want to know the answer to this exact question. This being an XML is of no particular importance, this could be any text file. — Christian
– Christian, Commented Dec 14, 2021 at 10:03

Mathias R. Jessen · Accepted Answer · 2021-12-14 10:33:56Z

1

Get-Content outputs each line as a separate string. To emulate the same behavior, split the string after > instead of appending a linebreak:

Get-Content P:\Webservice\21*_*CR_d*.xml |ForEach-Object { $_ -split '(?<=>)' } | Select-String -Pattern '.*<\/LIFNR>'

The construct (?<=...) is a lookbehind assertion - this way, PowerShell will split on a zero-length string immediately after >

answered Dec 14, 2021 at 10:33

Mathias R. Jessen

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Christian Over a year ago

Thank you for your help, it works perfectly! Just for clarification so I really get this: The -replace leaves the XML input still in a single one line string which is then piped to Select-String which matches the first occurence and returns the entire line of that occurence, hence the entire string. Saving and retrieving from a file "splits" the string because of the newlines and thus Select-String is fed single lines. U doing the split is basically doing the same?

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