Powershell script creating snapshots from folders using 7zip archiver.

create_snapshot.ps1

param (
    # if parameter "-i" Input Path was not specified, folder from which script has been invoked will be used
    [string]$i = "#", 
    # if parameter "-f" Include File was not specified, all files/folders will be processed
    [string]$f = "#", 
    # parameter "-o" Output Folder is required
    [string]$o = "#",
    # parameter "-a" specifying archiver command
    [string]$a = 'c:\Program Files\7-zip\7z.exe'
)

if(!(Test-Path $a )){
    write-output "Specified archiver program does not exist: '$a'"
    write-output "Use parameter -a <full_archiver_name> to specify one."
    exit 1
}

if(!(Test-Path $f )){
    write-output "Specified include file does not exist: '$f'"
    write-output "Use parameter -f <include_file_name> to specify one."
    exit 2
}

if(!(Test-Path -Path $i )){
    write-output "Specified input folder does not exist: '$i'"
    write-output "Use parameter -i <input folder> to specify one."
    exit 2
}

if($o -eq "" -or !(Test-Path -Path $o )){
    write-output "Specified output folder does not exist: '$o'"
    write-output "Use parameter -o <output folder> to specify one."
    exit 2
}

# change current folder to input folder so 7zip will include only relative paths
cd $i

# archive type - 7zip supports zip archives too, 
# but they do not support "delete" commend when extracting delta archive,
# so it is better to use 7z archives
$arctype = '-t7z'
$fExt = '.7z'

# update switches
$upSwitches = 'p0q3x2z0'

# get file handle
$fi = Get-Item $f

# full include filename including cmdline switches
$incFile = $('-ir@' + $fi.FullName) 
    
# base archive name
$baseArcName = $($o + "\" + $fi.BaseName)

# archive file containing changed files
$deltaArcName = $($baseArcName + " changes " + $([datetime]::now.tostring("yyMMddTHHmmss")) ) 

# run archiver
& $a 'u' '-r' $arctype $($baseArcName+$fExt) $('-u'+$upSwitches+'!'+$deltaArcName+$fExt) $incFile