Regex not working in Powershell

Question

I have a Powershell file myfile.ps1:

function Do-It
{
    $items = # A command that returns a collection of strings like:
             # Element 12657 - <Description trext>
             # Element 12656 - <Description trext>
             # Element 12655 - <Description trext>
             # ...

    $pattern = 'Element\s(\d*).*';
    foreach ($item in $items) {
        $res = $item -match $pattern;
        $len = $matches.Length;
        $id = $matches[0];
        Write-Output "$len $id";
    }
}

The problem is that my output is:

1 Element 12657 - <Description trext>
1 Element 12656 - <Description trext>
1 Element 12655 - <Description trext>
...

So no match found. However, if I execute this from cmd, then I get results.

What am I doing wrong? Need to escape something? Thanks

$matches is Hashtable. Hashtable does not have Length property. For PowerShell V3+, auto property Length will return 1 regardless of content of hash table. — user4003407
– user4003407, Commented Jun 19, 2015 at 13:49

Bacon Bits · Accepted Answer · 2015-06-19 13:38:25Z

2

Take a look and see what it's doing manually:

PS U:\> $item = 'Element 12657 - <Description trext>'
PS U:\> $pattern = 'Element\s(\d*).*'
PS U:\> $Matches

Name                           Value
----                           -----
1                              12657
0                              Element 12657 - <Description trext>

I would try $id = $matches[1];.

answered Jun 19, 2015 at 13:38

Bacon Bits

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1 Comment

Andry Over a year ago

Damn, stupid me... I knew the first or the last was the whole, did not look at numbers in the first column and thought it was a 0. Thanks

Antoine Aubry · Accepted Answer · 2015-06-19 13:39:14Z

1

The first match of a regular expression is the entire matched string. So, the match that you want is $matches[1]. I believe that $Matches.Length returns 1 because it is a list of matches with one single match that contains two groups.

answered Jun 19, 2015 at 13:39

Antoine Aubry

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