Deleting records from a log/text file - powershell

Question

I have several laptops that are generating daily activity logs for a process into txt files. I've figured out how to write a script to append the logs into one master file on a daily basis, but now I'm concerned about file size. I'd like to keep a rolling 60 days of data in my master file.
Here is my data format:
2016-06-23T04:02:33,JE5030UA,88011702312014569339,0000000034626,01451560610600980
Using Get-Date.AddDays(-60) I can get the cutoff date, but it's in MM/dd/yyy format.
If I set up a variable to get the date in the same format as my file (Get-Date -format 'yyyyMMdd), I can't use the .AddDays() method with it to get the cutoff date.
That's how far I've got so far. I'd include code, but there's not much there. The script to append the files was so easy. I can't believe it's difficult to purge old records.
My questions:
What am I missing on the date issue?
What is the best cmdlet to purge records > 60 days? There doesn't appear to be a 'delete' cmdlet for records in a file. I was expecting a 'if date > 60 days, then delete record' kind of function.
Do I need to add a header to the text file?

Answer 1

Take a look at the following code to read from your combined log and then filter out rows that are within your date range. You get a DateTime object from (get-date).AddDays(); you get a DateTime object from the time stamp in the file, then you can compare them. This is one way of doing it anyway.
$cutoffDate = (get-date).AddDays(-60);
$fileContents = get-content C:\your\path\combinedLog.txt
foreach($line in $fileContents)
{
write-host "Current line = $line"
$words = $line.Split(',')
$date=get-date $words[0];
write-host "Date of line = $date"
if($date -gt $cutoffDate)
{
# Append $line to your trimmed log
}
}

Answer 2

Since you're using an ISO date format you can remove records older than a given cutoff date by formatting the cutoff date accordingly and comparing the first field of each line to it:
$file = 'C:\path\to\your.log'
$cutoff = (Get-Date).AddDays(-60).ToString('yyyy-MM-dd\THH:mm:ss')
(Get-Content $file) |
Where-Object { $_.Split(',')[0] -ge $cutoff } |
Set-Content $file
However, rotating logs is usually a better appraoch than clearing out a single file. Write your logs to a different file each day, e.g. like this:
... | Set-Content "C:\path\to\master_$(Get-Date -f 'yyyyMMdd).log"
so you can simply remove logs by their last modification date:
$cutoff = (Get-Date).AddDays(-60)
Get-ChildItem 'C:\log\folder\master_*.log' |
Where-Object { $_.LastWriteTime -lt $cutoff } |
Remove-Item