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stringpowershellcharacter
Madhusudan
Madhusudan

Reputation: 4815

How to get alternating characters from a string in PowerShell?

I am working on a script in which I have to read alternating characters from a string.

I am using the following approach:

$s = "abcdef"
$chars = $s.ToCharArray()
For( $i = 0; $i -lt $chars.Count; $i = $i + 2){
    $chars[$i]
}

Is there a simpler approach, especially one based on a pipeline?

Upvotes: 2

Views: 491

Answers (4)

mjolinor
mjolinor

Reputation: 68301

Another possibility:

$string = 'abcdefg'
$i=0
([char[]]$string).where({$i++ %2})
b
d
f

Upvotes: 3

Martin Brandl
Martin Brandl

Reputation: 58981

You could use a simple regex (demo) to match two characters and replace it with the first one:

 $s -replace '(.).', '$1'

Output:

ace

If you want to have characters, just cast it to an char[]:

[char[]] ($s -replace '(.).', '$1')

or split the string (thanks PetSerAl):

$s -replace '(.).', '$1' -split '(?!^|$)'

Upvotes: 5

Matt
Matt

Reputation: 46710

Love the regex answer but wanted to include something that used the pipeline more and Select-Object

$string = "abcdef" 
[char[]]$string | Select-Object -Index (0..($string.Length-1) | Where-Object{$_ % 2})

-Index takes the length of the string and returns and array of odd numbers used to extract the characters from the char array. Using !($_ % 2) would alternate the returned set. In both cases I am taking advantage of the value returned by the modulus operator. If the number is even in the above example 0 is returned which evaluates to false. $_ % 2 -eq $false would accomplish the same thing and be more readable depending.

Upvotes: 3

Andrey Marchuk
Andrey Marchuk

Reputation: 13483

Not sure if it's simpler, but it's different:

$s = "abcdef"
for ($i = 0; $i -lt $s.Length; $i++)
{
    if ($i % 2 -ne 0)
    {
        $s[$i]
    }
}

Upvotes: 2

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