Powershell function returning an array instead of string

Question

i'm importing a csv and i would like to add a column to it (with the result based off of the previous columns)

my data looks like this

host address,host prefix,site
10.1.1.0,24,400-01

i would like to add a column called "sub site"

so I wrote this module but the problem is, the actual ending object is an array instead of string

function site {
    Param($s)
    $s -match '(\d\d\d)'
     return $Matches[0]
}

$csv = import-csv $file | select-object *,@{Name='Sub Site';expression= {site $_.site}}

if I run the command

PS C:\>$csv[0]

Host Address :10.1.1.0
host prefix  :24
site         :400-01
sub site     : {True,400}

when it should look like

PS C:\>$csv[0]

Host Address :10.1.1.0
host prefix  :24
site         :400-01
sub site     : 400

EDIT: I found the solution but the question is now WHY.

If I change my function to $s -match "\d\d\d" |out-null I get back the expected 400

Answer 1

Good you found the answer. I was typing this up as you found it. The reason is because the -match returns a value and it is added to the pipeline, which is all "returned" from the function.

For example, run this one line and see what is does:

"Hello" -match 'h'

It prints True.

Since I had this typed up, here is another way to phrase your question with the fix...

function site {
    Param($s)
    $null = $s -match '(\d\d\d)'
    $ret =  $Matches[0]

    return $ret
}

$csv = @"
host address,host prefix,site
10.1.1.1,24,400-01
10.1.1.2,24,500-02
10.1.1.3,24,600-03
"@

$data = $csv | ConvertFrom-Csv

'1 =============='
$data | ft -AutoSize

$data2 = $data | select-object *,@{Name='Sub Site';expression= {site $_.site}}

'2 =============='
$data2 | ft -AutoSize