Powershell - Remove from string

Question

Im extracting a list of IPs from a JSON file using the following syntax

$Request = 'https://url-to-json.com/file.json'
$AWSIPs = Invoke-WebRequest $Request | ConvertFrom-Json | Select-Object prefix -ExpandProperty prefixes -ExcludeProperty ("/.*") | Where-Object -Property "service" -EQ "service_name" | select ip_prefix
foreach ($awsip in $AWSIPs){
echo $awsip
}

This returns a list of IPs in this manner: - 0.0.0.0/00

0.0.0.0/00
0.0.0.0/00
0.0.0.0/00
0.0.0.0/00
0.0.0.0/00

I need to use this list of IPs, however before I can do so I need to remove the /00 at the end (obviously that's not 00 but it's the subnet mask, which is rarely ever identical).

I'd greatly appreciate help with this.

Thanks.

mklement0 · Accepted Answer · 2017-07-13 19:22:10Z

4

A -replace-based solution:

$ips =  '0.0.0.0/00',
        '0.0.0.1/01',
        '0.0.0.2/02',
        '0.0.0.3/03',
        '0.0.0.4/04'

$ips -replace '(.*)/.*', '$1'

Note how you can use an array directly as the LHS of the -replace operation.

The above yields:

0.0.0.0
0.0.0.1
0.0.0.2
0.0.0.3
0.0.0.4

-split is an option too, but to avoid additional complexity you need an explicit loop:

foreach ($ip in $ips) {
  ($ip -split '/')[0]
}

It is possible to avoid an explicit loop, but that's probably not worth doing - for reasons of both performance and readability; it does show PowerShell's flexibility, however:

($ips -split '/')[(0..($ips.Count-1)).ForEach({ $_ * 2 })]

edited Jul 13, 2017 at 19:22

answered Jul 13, 2017 at 18:59

mklement0

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