CODEWITHSUNDEEP
powershell
lara400
lara400

Reputation: 4736

pull text between characters

How do I pull text between two words? I know regex can do this and I have been looking around but the code I try just does not work for me at all...as clueless as a brick with regex...so probably am doing it totally wrong...

I have a text file and want to query whatever is displayed between these text strings:

[Problem Devices]

Device PNP Device ID Error Code

[USB]

I tried doing this but getting no where!

$devices = Get-Content c:\temp\dev.txt | out-string [regex]::match($devices,'(?<=\<Problem Devices\>).+(?=\<USB\>)',"singleline").value.trim()

You cannot call a method on a null-valued expression.
At line:1 char:141
+ $devices = Get-Content c:\temp\dev.txt | out-string [regex]::match($devices,'(?<=\<Problem Devices\>).+(?=\<USB\>)',"
singleline").value.trim <<<< ()
    + CategoryInfo          : InvalidOperation: (trim:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

Upvotes: 1

Views: 3486

Answers (2)

mjolinor
mjolinor

Reputation: 68331

If you're not comfortable with regex, there are other ways:

$test = $false

$devices = get-content file.txt |

foreach {

if ($_.trim() -eq '[Problem Devices]'){$test = $true}

elseif ($_.trim() -eq '[USB]') {$test = $false}

elseif ($test){$_}

} | where {$_.trim()}

Upvotes: 0

alroc
alroc

Reputation: 28194

Piping to out-string is not needed; get-content is sending each line of the file into the pipeline as a separate object. So you want to iterate through those objects with a foreach-object.

$devices = Get-Content c:\temp\dev.txt | foreach-object{[regex]::match($devices,'(?<=\<Problem Devices\>).+(?=\<USB\>)',"singleline").value.trim()}

However, you are still left with the problem of attempting to trim() a null object - if your regex match doesn't find a match, you can't call value.trim().

Your regex tries to match on <Problem Devices> when your input file has [Problem Devices].

Rather than try to do everything in a single set of pipeline steps, break your problem down:

  1. For each line in the file, check for [Problem Devices]
  2. For each subsequent line, if it is [USB], exit the loop. If it is not [USB], capturing each line into a variable (build an array of these lines)
  3. After the loop, iterate over each element of the array you just built to parse each value out (creating a collection of PSObjects (one per device), or a collection of hashes (one per device), depending on your needs).

Upvotes: 1

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