Powershell - compare time in log file

Question

Hello everyone, can you help me with this question? I need to compare two strings with time. I have a log file that contents information looks like that: 22.03.2021 18:59:16.111 | some information.... I need to get frome there only information about time and compare it with time is now. So I have a script:

$MD = get-date - format "HH:MM:s"
     $path = some path to log file 
    $a = get-content -path $path -tail 1
     $b = $a.SubString(11,8)

Then i need to use if statements as I think:

If (($MD).AddHours(-0,5) -gt $b) {do something} 
    else {do anotherthing}

But it will not works because $mb and $b is a string data :( how I can compare it?

Answer 1

Hi，

PowerShell converts $b into a datetime object automatically. Actaully it's (get-date).AddHours(-0,5) -gt [datetime]$b. You can also try

([datetime]$MD).AddHours(-0.5) -gt [datetime]$b  

Best Regards,
Ian Xue

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Answer 2

See if this makes more sense:

$a = '1234567890112:10:139876'  # contains log file date data
$MD = (Get-Date).AddHours(-0.5)
$b = get-date $a.Substring(11,8)    # assumes that time is in 24 hour format (no AM/PM necessary)

if ($MD -gt $b){
    "{0:HH:MM.s} > {1:HH:MM.s}" -f $MD, $b
}
else{
    "{0:HH:MM.s} <= {1:HH:MM.s}" -f $MD, $b
}

It's better if you don't treat date/time as strings. That almost always leads to grief. Get the information into a DateTime object and your comparisons will make a lot more sense.

Answer 3

Miracle...
If change

If ((get-date).AddHours(-0,5) -gt $b)

All is works... but still can't understand how it works if $b looks like a string data oO?