Use Powershell to match and print specific column from output

Question

I want to fetch a specific column from an output of a command. Can someone please suggest what is the best way to do it?

The command used is - choco list -lo which gives the output as

Chocolatey v0.10.15
chocolatey 0.10.15
erlang 22.3
rabbitmq 3.8.11
3 packages installed.

And from the given output the only required value is 3.8.11 which is the version of rabbitmq.

I have already tried this but it does not work - choco list -lo | Select-String -Pattern "rabbit" | %{ $_.Split(' ')[1]; }

Can someone suggest how can we do this?

Thanks in advance :)

zett42 · Accepted Answer · 2021-02-28T08:34:00.110

2

Try this:

choco list -lo | 
    Select-String -Pattern "rabbitmq (.+)" | 
    ForEach-Object { $_.Matches.Groups[1].Value }

Output of Select-String is a MatchInfo object, so you need to query its members to get the matched value.

I'm using a group (.+) to enable extraction of the version number without further string operations. The groups value is then read in the ForEach-Object ¹ script block through $_.Matches.Groups[1].Value. In this expression the index 1 specifies the first group (index 0 would specify the whole match).

[1] ForEach-Object is abbreviated by %

edited Feb 28 '21 at 08:34

answered Feb 22 '21 at 20:04

zett42

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In the answer, it is `.+` but in the explanation, you have mentioned `.*`, which one is more accurate? I am assuming it to be `*.`. Although, I was able to get the required output from both of them. – Ismail Feb 23 '21 at 04:55
@Ismail `.*` matches any character, zero or more times and `.+` matches any character, one or more times. I think the latter is more correct because we are expecting at least one character for the version. – zett42 Feb 23 '21 at 07:22

postanote · Answer 2 · 2021-02-23T09:46:05.570

There is no comma to split on based on what you posted. It's a space...

I don't have choco installed, because I don't have a use case for it. So, a pseudo list is being:

Option1:

Clear-Host
$ChocoList = @'
Chocolatey v0.10.15
chocolatey 0.10.15
erlang 22.3
rabbitmq 3.8.11
'@ -Split "`n"

$ChocoList | 
ForEach {
    (
        $PSItem | 
        Select-String -Pattern 'rabbitmq'
    ) -Split (' ')
}
# Results
<#
rabbitmq
3.8.11
#>

Option2

([regex]::Matches($ChocoList,'rabbitmq.*').Value -split ' ')
# Results
<#
rabbitmq
3.8.11
#>

Upadated as per my comment back to yours - Option1:

Clear-Host
$ChocoList = @'
Chocolatey v0.10.15
chocolatey 0.10.15
erlang 22.3
rabbitmq 3.8.11
'@ -Split "`n"

($ChocoList | 
ForEach {
    (
        $PSItem | 
        Select-String -Pattern 'rabbitmq'
    ) -Split (' ')
})[1]
# Results
<#
3.8.11
#>

Updated as per my comment back to yours - Option2

([regex]::Matches($ChocoList,'rabbitmq.*').Value -split ' ')[1]
# Results
<#
3.8.11
#>

Thanks, @postanote, my requirement is to get only the version nothing else. So the first solution does the trick for me. — Ismail, Feb 23 '21 at 04:56
Each will get the version. You just have to select it by the index number. Meaning, just add [1] to the even of either one. as updated. All presented responses are doing the same thing. — postanote, Feb 23 '21 at 09:42

Use Powershell to match and print specific column from output

2 Answers2