Powershell - edit and then save existing file

coreypoulton · 2019-02-20T17:51:44.000Z

Hi everyone!

We have a log file that eventually gets too big (30,000 lines). So, we have to manually edit it and delete the top 5000 lines regularly.

Would like to have a simple PS script we can add to task scheduler to automate this for us.

Any help would be greatly appreciated.

Copy the active log file, appending current date/time to the end of the file name
Edit original log file to delete all lines over 25000 and save.

Thanks,

Corey

Neally · 2019-02-20T18:40:14.000Z

What have you tried so far? Where are you stuck?

Can you have whatever creates the log split the log once it reached a certain size?

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Evan7191 · 2019-02-20T18:41:00.000Z

What have you tried? We can help you with a script, but we do not write scripts from scratch on demand.

coreypoulton · 2019-02-20T18:47:01.000Z

I’m very new to PS, so I’ve gotten quite intimate with Google and Spiceworks on this issue over the last couple of days … this is what I have so far;

# Rename the file
cd "E:\path\"
ren "logfile.txt" $("logfile_"+$(Get-Date -format yyyyMMdd_HHmmss)+".txt")

# Remove all lines over 25,000 from the top

# Delete all files older than x days
$Path = "E:\path\"
$Daysback = "-x"
 
$CurrentDate = Get-Date
$DatetoDelete = $CurrentDate.AddDays($Daysback)
Get-ChildItem $Path | Where-Object { $_.LastWriteTime -lt $DatetoDelete } | Remove-Item

I’m not sure where to start on the issue of editing the file.

anthony7445 · 2019-02-20T18:48:14.000Z

well,

$file1="\\server\share\file.txt"

(Select-String -Pattern "\w" -Path $file1 | foreach {$_.line} | Select-Object -Skip 25000 | Out-File -FilePath $file1)

you could try that.

Neally · 2019-02-20T18:48:37.000Z

Pick file, select first 25000 lines, save it.

# an idea
get-content $LogFile |
select-object -first 25000 |
out-file $logFileNew

kevinboutelle · 2019-02-20T18:52:13.000Z

I do this in the script that I run every morning, M-F with the exception of saving the old data.

You could easily add a line that simply copied the file as is and saved it as a new file before doing the following.

Set your max lines as what you want left in the file.

$maxLines = 200
$logFile = "C:\MyFolder\output.log"

# Trim the max size of the log file
(Get-Content $logFile -tail $maxLines -ReadCount 0) | Set-Content $logFile

martin9700 · 2019-02-20T18:56:04.000Z

One last option that does exactly what you’re asking for:

$Log = Get-Content c:\Path\To\Logfile.txt | Select -Skip 5000
$Log | Out-File c:\Path\To\Logfile.txt

edwineekelaers2 · 2019-02-20T18:59:34.000Z

Stop mixing batch and PowerShell and your life will become a lot easier. Made that mistake too in the beginning and had some freaky unexplainable results due to invisible characters. It’s hard in the beginning but try and dont be afraid to post your code for critique. Learn from the critique.

coreypoulton · 2019-02-20T19:24:19.000Z

Yeah, I inherited the file from another person that had originally made the renaming part of the script. I added the code to delete after x amount of days and those two seem to be testing okay. So, I thought I’d just rewrite the original renaming part later. I’m always willing to accept some constructive feedback and critiquing … so feel free to fire away

coreypoulton · 2019-02-20T19:33:12.000Z

Martin9700:

One last option that does exactly what you’re asking for:
$Log = Get-Content c:\Path\To\Logfile.txt | Select -Skip 5000
$Log | Out-File c:\Path\To\Logfile.txt

Worked like a charm, thank you and thanks so much to everyone for all of your quick replies.

Love this site!

coreypoulton · 2019-02-20T20:22:15.000Z

Just an update, this is what i have now. If anyone would like to critique it, please feel free.

# Copy and rename the file
Copy-Item "C:\test\file.txt" "C:\test\backup\file_$(Get-Date -format "yyyyMMdd").txt"

# Remove all lines over 25000 from the top
$Log = Get-Content C:\test\file.txt | Select -Skip 25000
$Log | Out-File C:\test\file.txt

# Delete all files older than 3 days
$Path = "C:\test\backup\"
$Daysback = "-3"
 
$CurrentDate = Get-Date
$DatetoDelete = $CurrentDate.AddDays($Daysback)
Get-ChildItem $Path | Where-Object { $_.LastWriteTime -lt $DatetoDelete } | Remove-Item

Again, thanks to everyone that took time out of their day to help

martin9700 · 2019-02-21T08:00:39.000Z

Might want to consider copying the file to backup daily, like ALL of it. That way you isolate logs from a particular day. The 25000 lines may or may not be the same day, there will probably be overlap. Might make finding the log you’re looking for more difficult. Something like:

Move-Item "C:\test\file.txt" "C:\test\backup\file_$(Get-Date -format "yyyyMMdd").txt"
New-Item "c:\test\file.txt" -ItemType File  #this step might not be necessary if the application will just create the log file if it doesn't exist

#Clean up old logs
Get-ChildItem "c:\test\backup\*" | Where-Object { $_.LastWriteTime -lt (Get-Date).AddDays(-3) } | Remove-Item