PowerShell Strings

Question

I extract some data from my computer and it creates either a variable or I've written it to a .txt file. The output looks like this:

RVR7RYR

I I only need the first 7 characters so I wrote this:

$line = get-content "c:\temp\file.txt"
$var = $line
$result = $var.SubString($var.length - 7, 7)
$result

It gives me this error:

Exception calling "Substring" with "2" argument(s): "StartIndex cannot be less than zero. Parameter name: startIndex" At line:5 char:1

$result = $var.SubString($var.length - 7, 7)

  + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
  + FullyQualifiedErrorId : ArgumentOutOfRangeException

my file does have spaces inbetween the values and even after the second value, not sure if that matters.

how do I get just the first 7 characters?

1) First (as a debugging method), echo "$var" and $var.length" to make sure they're really what you think they are. 2) Q: Why not simply $result = $var.SubString(0, 7)? — paulsm4
– paulsm4, Commented Nov 29, 2021 at 18:08
Hello. when I echo "$var" it shows me both occurrences of the string. When I run "$result = $var.SubString(0,7) I get the exact same error as shown above. — Q7777777
– Q7777777, Commented Nov 29, 2021 at 18:13
Thank you for trying; sorry it didn't help. Let me try to reproduce the problem myself. — paulsm4
– paulsm4, Commented Nov 29, 2021 at 19:08

halfer · Accepted Answer · 2023-12-09 12:56:34Z

0

The problem was that you were inadvertently reading an ARRAY, not just a single text string.

.ps1:

$line = get-content "c:\temp\file.txt" 
echo "line: " $line ", line.length: " $line.length ", line[0].length: " $line[0].length
$result = $line[0].SubString(0, 7)
echo "result: " $result

Sample output:

line:
RVR7RYR

RVR7RYR

cow pig chicken goat
, line.length:
5
, line[0].length:
7
result:
RVR7RYR

In other words, you want to take the first 7 characters of the first line ($line[0]).

edited Dec 9, 2023 at 12:56

halfer

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answered Nov 29, 2021 at 19:21

paulsm4

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