Having difficulty getting multi-line Powershell regex to work - no matches

Question

I referred to several examples I was able to search, which seemed highly pertinent, but am still unable to get this to work.

My input looks like this, from a dhcp server stats command, and I've confirmed that $output is getting defined properly with lines that look like:

MIBCounts:
        Discovers = 63911.
        Offers = 3903.
        Delayed Offers = 0.
        Requests = 29199.
        Acks = 273080.
        Naks = 71.
        Declines = 0.
        Releases = 395.
        ServerStartTime = Tuesday, March 27, 2012 7:38:53 PM
        Scopes = 34.
        Scopes with Delay configured= 0.
        Subnet = 10.31.0.0.
                No. of Addresses in use = 203.
                No. of free Addresses = 40774.
                No. of pending offers = 0.
        Subnet = 10.32.3.0.
                No. of Addresses in use = 0.
                No. of free Addresses = 0.
                No. of pending offers = 0.
        Subnet = 10.32.100.0.
                No. of Addresses in use = 48.
                No. of free Addresses = 145.
                No. of pending offers = 0.
        Subnet = 10.32.101.0.
                No. of Addresses in use = 34.
                No. of free Addresses = 159.
                No. of pending offers = 0.

So what I tried was this, but got no matches:

$output=$(netsh -r myserver dhcp server show mibinfo)

$dhcp_regex=@"
(?s)Subnet = (\d\.\d\.\d\.\d)\.\W+
.*No\. of Addresses in use = (\d+)\.\W+
.*No\. of free Addresses = (\d+)\.\W+
"@

$dhcp_record= {
    @{
        subnet=$matches[0]
        inuse=$matches[1]
        free=$matches[2]
    }}


$output -match $dhcp_regex

$matches

Assistance appreciated.

northben · Answer 1 · 2012-04-20T13:26:07.703

3

Try this for your first line instead:

(?s)Subnet = (\d+\.\d+\.\d+\.\d+)\.\W*

You'll also want to look at each line separately:

$output | % { $_ -match $dhcp_regex }

# Append | Out-Null if you don't want each line printed on your screen.

$matches[1]

Edit: here is a more complete example.

$dhcp_regex = 'Subnet = (\d+\.\d+\.\d+\.\d+)'
$dhcp_regex2 = 'in use = (\d+)'
$output | ? { $_ -match $dhcp_regex -or $_ -match $dhcp_regex2} | % { $Matches[1] }

Edit: here is a multiline example.

$dhcp_regex = '(?m)Subnet = (\d+\.\d+\.\d+\.\d+)\.\r\n.*in use = (\d+)'
$output | Out-String | % { $_ -match $dhcp_regex }
$matches

hat tip: http://www.vistax64.com/powershell/80160-powershell-regex-help.html

Edit: Looks like (?m) is not actually necessary. Out-String is the secret sauce.

edited Apr 20 '12 at 13:26

answered Apr 19 '12 at 20:15

northben

382
1
4
13

Ok, tried the first, nothing. Tried the second, and yes, it works, but it doesn't really represent the "inline, need to match the whole pattern" objective. If it happened to get 2 lines of "in use" in a row, I'd still get output. In this particular case, our input format we're parsing is extremely well known, and we can rely on the pattern of alternation being followed. For me however, I treat these situations as instructive and want rigorous solutions that will stand up when I know my data input is not as clean. I'd like to make the original form work as it's more exact. – Kevin Apr 19 '12 at 23:05
Fair enough. That's how I approach these things too. I will amend my comment with another approach. – northben Apr 20 '12 at 13:24

score 1 · Answer 2 · answered Apr 23 '12 at 20:54

1

Changed the regex you provided to add the extra data element.

$dhcp_regex='(?m)Subnet = (\d+\.\d+\.\d+\.\d+)\.\r\n.*in use = (\d+)\.\r\n.* free Addresses = (\d+)\.'

That works fine now - much appreciated! I may spend some time when I'm bored (hehe) to discover in what nuanced way what we were doing before was failing.

answered Apr 23 '12 at 20:54

Kevin

11
1

1

Was this to be a comment on @northben's answer? If so, please move.. If this was intended to be the correct answer, don't forget to mark it as "accepted". – jscott Apr 24 '12 at 12:33

Having difficulty getting multi-line Powershell regex to work - no matches

2 Answers2