Converting to Powershell

Question

I have this perl code I am trying to convert to powershell.

foreach my $f ( @file_list ) {
    if( $f =~ /^([\d]+)_${base_ver}_([\d]{4})\.zip$/i ){
        $pfile = $f;
        ( $pnum, $pdate ) = ( $pfile =~ /^([\d]+)_${base_ver}_([\d]{4})\.zip$/i ); # need to convert
        ( $pmon, $pyear ) = ( $pdate =~ /^(\d\d)(\d\d)$/ ); # need to convert
        if( ($patch_nbr == 0) || ($patch_nbr == $pnum) ) {
            $fcnt++;
        }
    }
}

I've converted most of it here..

$file_list = Get-ChildItem -force $base_dir
$file_list | foreach-object {
    if($_ -match "/^([\d]+)_${base_ver}_([\d]{4})\.zip$/i"){
        $pfile = $_


        if($patch_nbr -eq 0 -or $pacth_nbr -eq $pnum){
            $fcnt++
        }
    }
}

Not quite sure how to convert the two variables that equal the regex or if there is a better way to convert the perl code to powershell than what I already have.

Mathias R. Jessen · Accepted Answer · 2015-08-24 17:17:02Z

3

The [mode]/pattern/[replace/][options] syntax from perl doesn't apply to regex in PowerShell.

Thus, your pattern

/^([\d]+)_${base_ver}_([\d]{4})\.zip$/i

becomes

^([\d]+)_${base_ver}_([\d]{4})\.zip$

(i is unnecessary, -match resolves to -imatch (case-insensitive match) by default)

To capture the number prefix and date, you can use a named capture group ((?<name>pattern)):

^(?<num>[\d]+)_${base_ver}_(?<date>[\d]{4})\.zip$

You can then grab the match from $Matches["name"]:

if($f -match "^(?<num>[\d]+)_${base_ver}_(?<date>[\d]{4})\.zip$"){
    $pfile = $f
    $pnum = $Matches["num"]
    $pdate = $Matches["date"]
    $pmon = -join $pdate[0..1]
    $pyear = -join $pdate[2..3]
}

You could also change the regex pattern to capture the month and year individually:

if($f -match "^(?<num>[\d]+)_${base_ver}_(?<month>[\d]{2})(?<year>[\d]{2})\.zip$"){
    $pfile = $f
    $pnum = $Matches["num"]
    $pmon = $Matches["month"]
    $pyear = $Matches["year"]
}

answered Aug 24, 2015 at 17:17

Mathias R. Jessen

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1 Comment

Hemi81 Over a year ago

Thanks Mathias R. Jessen! Helps a lot.

Ansgar Wiechers · Accepted Answer · 2015-08-24 17:47:36Z

2

I would put a Where-Object filter first. That allows you to use the $matches collection in the subsequent ForEach-Object without a second -match in a nested if statement. If you also change the date pattern from (\d{4}) to (\d{2})(\d{2}) you can assign $pnum, $pmon, and $pyear in a single statement. You could also simplify the condition for incrementing $fcnt. Instead of checking if $patch_nbr equals one of two values you could check if it's contained in an array of the two values.

Get-ChildItem -Force $base_dir |
  Where-Object { $_ -match '^(\d+)_${base_ver}_(\d{2})(\d{2})\.zip$' } |
  ForEach-Object {
    $pnum, $pmon, $pyear = $matches[1..3]
    if (0, $pnum -contains $patch_nbr) { $fcnt++ }
  }
}

Of course, if all you want to do is count the number of files matching a given patch number, you could just do something like this:

$f = Get-ChildItem -Force $base_dir | Where-Object {
       $_ -match '^(\d+)_${base_ver}_\d{4}\.zip$' -and
       0, $matches[1] -contains $patch_nbr
     }
$fcnt = @($f).Count

answered Aug 24, 2015 at 17:47

Ansgar Wiechers

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3 Comments

Hemi81 Over a year ago

Thanks for the input Ansgar Wiechers! Saves me an extra line. Also is there a way I can add a ?<date>, so I capture the whole date along with $pnum, $pmon, $pyear?

Ansgar Wiechers Over a year ago

@marc117 Sure. Simply change (\d{2})(\d{2}) to (?<date>(\d{2})(\d{2})) to get a named group, or to ((\d{2})(\d{2})) to get an additional unnamed group (so you can do the assignment like this: $pnum, $pdate, $pmon, $pyear = $matches[1..4]).

Hemi81 Over a year ago

Thanks again @Ansgar Wiechers!

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