Powershell script to delete oldest files (not relative to current date)

Question

I DO NOT want to "delete files older than X days." If I wanted to do this, I'd just pick one of the thousands of scripts out there that have already been written for that purpose, and I wouldn't bother asking such a trivial question on ServerFault.

I DO want to delete all but the most recent N files in a particular folder.

Background: a remote system is configured to dump a periodic archive files to a share on a Windows server. These files have a naming convention of YYYYMMDD-hhmm.ext. Should the archive process fail, I don't want the purge script to delete the files just because they are older than so-many-days. There is no way to configure the remote system to purge the files as part of the archive process.

So for example, when the script runs there may be 10 files, there may be 7 files, there may be 5 files in the folder. I need to always keep at least the most recent 5, regardless of how old they are.

Can this be done with PowerShell?

EDIT: it would be desirable to ignore files or folders not matching the naming convention. Other files and folders shouldn't be deleted, nor should they confuse the script (resulting in the retention of fewer than 5 archive files).

Answer 1

Usage: yourScript.ps1 -Path path\to\run\against [-NumberToSave N]

param([String]$Path,[Int32]$NumberToSave=5)

$items = Get-ChildItem "$Path\*.ext" |
    Where-Object Name -match "\d\d\d\d\d\d\d\d-\d\d\d\d\.ext" |
    Sort-Object Name -Descending

if ($NumberToSave -lt $items.Count)
{
    $items[$NumberToSave..($items.Count-1)] | Remove-Item
}

I don't expect this is really any better than @John's, I just made this to try parameters, regexp, and not using a loop. Doing a regex match does have the possible benefit of ruling out other files with .ext that don't match the format (e.g. 20130504-1200.txt.ext, 20.ext), but it's doubtful that applies.

I was bummed to find out that if $NumberToSave = $items.Count then the if statement is needed, otherwise it wouldn't be there. Technically:

$items[$numberToSave..$items.Count] | Remove-Item 

works fine (PowerShell doesn't seem to error if you reference past the array bounds, it just handles and ignores it?) but that seemed potentially confusing.

Answer 2

$n = x

$items = Get-ChildItem path_to_folder\*.ext

$items | 
  Sort-Object Name -Descending | 
  Select-Object -Last ($items.count - $n) | 
  Foreach-Object { Remove-Item $_ }

Answer 3

# Get all the items in `C:\Archive`
Get-ChildItem -Path 'C:\Archive' |

    # Skip directories
    Where-Object { -not $_.PsIsContainer } |

    # Only get files that match YYYYMMDD-HHMM.ext format
    Where-Object { $_.Name -match '\d{8}-\d{4}.ext' } |

    # Sort them by name, from most recent to oldest
    Sort-Object -Descending -Property Name |

    # Keep the first five items
    Select-Object -Skip 5 |

    Remove-Item -WhatIf

Answer 4

A friend provided this script:

# Defines how many files you want to keep?
$Keep = 5

# Specifies file mask
$FileMask = "*.ext"

# Defines base directory path
$Path = "F:\path\to\backups\"

# Creates a full path plus file mask value
$FullPath = $Path + $FileMask

# Creates an array of all files of a file type within a given folder, reverse sort.
$allFiles = @(Get-ChildItem $FullPath) | SORT Name -descending 

# Checks to see if there is even $Keep files of the given type in the directory.
If ($allFiles.count -gt $Keep) {

    # Creates a new array that specifies the files to delete, a bit ugly but concise.
    $DeleteFiles = $allFiles[$($allFiles.Count - ($allFiles.Count - $Keep))..$allFiles.Count]

    # ForEach loop that goes through the DeleteFile array
    ForEach ($DeleteFile in $DeleteFiles) {

        # Creates a full path and delete file value
        $dFile = $Path + $DeleteFile.Name

        # Deletes the specified file
        Remove-Item $dFile
    }
}

Answer 5

This works for me using powershell v5.1

Get-ChildItem -Path C:\Path\To\Logs\BaseName*.log | Sort-Object -Descending | Select-Object -Skip 5 | Remove-Item

Answer 6

I've done this in Bash before, and you may be able to translate it to PowerShell. Personally, I'm a Linux admin, and don't know enough about Windows/PowerShell to do so myself.

#!/bin/bash

# Directory with backups in need of cleaning
bkps_dir="/opt/bkps/hosting.madyork.com"

# Make sure that there are at least 7 days worth of backups to avoid removing
#   the only backups left.
if [ "$(/bin/find "${bkps_dir}" -maxdepth 1 -type d | /usr/bin/wc -l)" -lt 8 ]; then
    echo "Less than 8 backups found!"
    echo "Will not delete anything!"
    echo "Exiting..."
    exit 1
fi

/bin/find "${bkps_dir}" -maxdepth 1 -type d -mtime +7 -print0 | /usr/bin/xargs -0 /bin/rm -rf

Sorry that I could not be more helpful.

Edit: I also placed this here in case a Linux admin is in need of similar info.