With the SFTP ports in BizTalk 2013, we are using the log function. BizTalk appends each SFTP log to the end of the existing log file.
So I created a Powershell Script to take an array of directory names, and run the same re-run and delete logic for each.
I also include the logic to delete a file over a certain retention period (see also shorter code for that in prior post: “Powershell to Delete Old Files“).

#################################################################
#
#
# Neal Walters - 09/05/2017
# Script: RenameSFTPLogsToAddDate.ps1
# Purpose: Rename a file such as "receive_internal.txt" to
#          "receive_internal_2017_09_01.txt"
#  so that each day has it's own separate file of SFTP messages.
#  Also purge files over $retentionDays
#  Use Task Scheduler to schedlue this script
#  to run once late a night or early morning.
#
#################################################################

cls
$retentionDays = 30
$formatDateTime = get-date -f _yyyy_MM_dd__HH_mm_ss
$formatDate = get-date -f _yyyy_MM_dd
Write-Host “formatDateTime= $formatDateTime”
Write-Host “——————————————————-”
$renameCount = 0
$skipCount = 0
$deleteCount = 0

# Array of Directory Names (logic below will process each directory you specify here)
$DirNames = “d:\BizTalk\App1\SFTPLogs\”,
“d:\BizTalk\App2\SFTPLogs\”

Foreach ($DirName in $DirNames)
{
Write-Host “DirName=$DirName”
Get-ChildItem $DirName -Filter *.txt |
Foreach-Object
{

$fullname = $_.FullName.ToString();
$dirname = $_.Directory.ToString();
$filename = $_.Name.ToString();
$filenameOnly = [io.path]::GetFileNameWithoutExtension($filename)
$ext = [io.path]::GetExtension($filename) # this includes the ., for example .txt

#If filename contains an underscore, then we think it has a date in it.
#If no date found, we want to rename the file, otherwise leave it as it was.

# looking for 20 as the century… part of date 2017, 2018, 2019 etc…
# if (-Not ($filenameOnly.toString().Contains(“_20”) ) )
if (-Not ($filenameOnly -Match “_20”) )
{
Write-Host “OldName $fullname”
$content = Get-Content $_.FullName
$formatDate = get-date -f _yyyy_MM_dd

Write-Host “Filename=$filename”
$newFileName = $dirname + “\” + $filenameOnly + $formatDate + $ext
Write-Host “NewName $newFileName`n”
Rename-Item $fullname $newFileName
$renameCount++
}
else
{
#Write-Host “Skipping file=$filenameOnly because no match”
$skipCount++
}

#purge files over retentionDays days old
if ($_.LastWriteTime.AddDays($retentionDays) -lt (GET-DATE) -and -not $_.psiscontainer)
{
REMOVE-ITEM $_.fullname -force
$deleteCount++
}
} #end of Foreach-Object
Write-Host “Number of Files Renamed = $renameCount”
Write-Host “Number of Files Skipped = $skipCount (for rename)”
Write-Host “Number of Files Deleted = $deleteCount”
Write-Host “——————————————————-”
}