Powershell error while saving string values into array

Question

I'm trying to save some dynamic string values in an array in my powershell script. As per my knowledge array index starts with 0 till n. Hence I initialize value of index with 0 as $n=0. The array saves value in the 0th location, but in the next loop of foreach when $n=1, it gives an error:

Index was outside the bounds of the array.

My script is like:

$arr = @(100)
$n=0
$sj=Select-String -Path C:\Script\main.dev.json -pattern '".*":' -Allmatches 
foreach($sjt in $sj.Line)
{
 Write-host "n=" $n
 Write-Output $sjt
 $arr[$n] = $sjt
 $s=Select-String -Path C:\Script\$js -pattern '.*"' -Allmatches 
 $n=$n+1
}

Output is:

n= 0
     "Share": "DC1NAS0DEV",
n= 1
     "Volume": "devVol",
Index was outside the bounds of the array.
At C:\Script\fstest.ps1:30 char:2
+  $arr[$n] = $sjt
+  ~~~~~~~~~~~~~~~
    + CategoryInfo          : OperationStopped: (:) [], IndexOutO
   on
    + FullyQualifiedErrorId : System.IndexOutOfRangeException

n= 2
     "DbServer": "10.10.10.dev"
Index was outside the bounds of the array.
At C:\Script\fstest.ps1:30 char:2
+  $arr[$n] = $sjt
+  ~~~~~~~~~~~~~~~
    + CategoryInfo          : OperationStopped: (:) [], IndexOutO
   on
    + FullyQualifiedErrorId : System.IndexOutOfRangeException

This means the array successfully saves the value of $sjt in the array when $n=0 but in the next 2 iterations when $n becomes 1 and 2 respectively it throws an error of 'Index was outside bounds'.

Below workarounds already tried, one by one and in combination:

$arr = @() or $arr = @(1000)
$arr[$n] = @($sjt)

Please assist as where I'm wrong and what needs to be corrected?

Drop the index referencing the array and do this $arr += $sjt which appends to the array. — t0mm13b
– t0mm13b, Commented Jun 12, 2017 at 21:33

BenH · Accepted Answer · 2017-06-12 21:35:45Z

3

@(100) is an array with only one element, 100. Not an array of 100 elements. You could use $array = 0..99 to make an array with 100 elements. But I don't think that's what you want.

You could make an empty array and then add elements to it.

$arr = @()
foreach ($sjt in $sj.Line) {
    $arr += $sjt
    $s = Select-String -Path C:\Script\$js -pattern '.*"' -Allmatches 
    $n = $n+1
}

Alternatively (and slightly more efficiently), you could set variable to be equal to the output of your loop and output the value.

$arr = foreach ($sjt in $sj.Line) {
    $sjt
    $s = Select-String -Path C:\Script\$js -pattern '.*"' -Allmatches 
    $n = $n+1
}

answered Jun 12, 2017 at 21:35

BenH

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3 Comments

Brite Roy Over a year ago

Issue resolved by simply using $arr += $sjt which is also suggested by t0mm13b above. But I'm curious to know why $arr[$n] = $sjt wont work by incrementing value of 'n' evrytime. This works well in in C++ and its logical as well. Do you know the reason?

BenH Over a year ago

@BriteRoy It would work if your array had enough elements. Which is what I identified at the beginning of the answer. This method works best if you know the exact number of array elements, otherwise as you noticed when you try to index into the array and that element does not exist you receive an error or you end up with extra elements in your array that are nonsensical. The += method creates a new array and copies the old values and the new value, so it's not super efficient. The third method has none of these drawbacks.

Brite Roy Over a year ago

Late to respond, but thanks for the explanation @BenH.

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