PowerShell RegEx with Select-String doesn't return any rows

Question

Using this reg-ex tester: http://myregextester.com/index.php Indicates my regex should work: Regex:

{name:"(\w*?)", rank:([\d]+)},

Sample Data to capture:

{name:"AARON", rank:77},
{name:"ABBEY", rank:1583},

Here's the powershell script I'm attempting to run , to parse json-like data into a powershell grid.

$regex = '{name:"(\w*?)", rank:([\d]+)},'

(Select-String -Path EmailDomains.as -Pattern $regex -AllMatches).matches |foreach {

$obj = New-Object psobject

$obj |Add-Member -MemberType NoteProperty -Name Rank -Value $_.groups[1].value

$obj |Add-Member -MemberType NoteProperty -Name Name -Value $_.groups[0].value

$obj

} |Out-GridView -Title "Test"

The reg-ex never seems to return values (I'm guessing its a MS regex versus Perl regex mixup, but I can't identify), so I'm not sure what the issue could be. Any help is appreciated!

VolatileRig · Accepted Answer · 2012-07-24 21:33:26Z

2

The question mark often has different functionality in different environments (in this one, I think it means "match the preceding character 0 or 1 times"). I doubt that it is the same as Perl's. Instead of

"(\w*?)"

Try:

"([^"]*)"

edited Jul 24, 2012 at 21:33

answered Jul 24, 2012 at 21:28

VolatileRig

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5 Comments

Richthofen Over a year ago

Thank you. Indeed, it appears once I corrected my reg-ex, I was good to go.

dugas Over a year ago

The question mark in this context tells the asterisk to not be greedy.

VolatileRig Over a year ago

If this were Perl, you would be correct. However, like I thought, Powershell sees a question mark as a match for 0 or 1 of the previous character. See the doc here.

dugas Over a year ago

It determines if a quantifier is greedy because it is placed after a quantifier. If it were not placed after a quantifier, then yes, it would make the preceding token optional.

VolatileRig Over a year ago

Interesting, I haven't seen anything in docs as far as dual functionality of the character, do you have a doc you can point to? I've had to find annoying workarounds because I just assumed that it doesn't control greediness, that would be great if you're correct.

zdan · Accepted Answer · 2012-07-24 21:31:03Z

1

Your expression:

(Select-String -Path EmailDomains.as -Pattern $regex -AllMatches)

returns an array of MatchInfo objects. The array itself does not have a Matches property.

What you have to do is expand the Matches property using the Slect-Object commandlet, then pass that along your pipeline:

Select-String -Path EmailDomains.as -Pattern $regex -AllMatches | select-object -expand Matches | foreach {

answered Jul 24, 2012 at 21:31

zdan

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1 Comment

Richthofen Over a year ago

Thank you. It appears that, combined with a change in the reg-ex, brought me to where I needed to go.

dugas · Accepted Answer · 2012-07-24 21:30:46Z

0

I don't think your regex is the problem. Matches is a property on each of the objects returned by Select-Object, not on the collection of objects returned.

$regex = '{name:"(\w*?)", rank:([\d]+)},'
$matches = (Select-String -Path .\a.txt -Pattern $regex)

$matches | Select -ExpandProperty Matches | Select @{n="Name";e={$_.Groups[1].Value}}, @{n="Rank";e={$_.Groups[2].Value}}

answered Jul 24, 2012 at 21:30

dugas

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