How to maintain a Session info in Powershell script - powershell

Question

I have script like below:
foreach ($var1 in (gc 1.txt)){
// my code logic
}
Here 1.txt file contains list of values like abc, xyz, pqr etc..,
If due to any of the script issues/ctrl+c stopped the script, need to restart the script from last stopped session.
To be clear if script has stopped at processing file at 'xyz' and when i restart the script it should process the logic from 'xyz' only but shouldn't restart from 'abc' again.
Please guide me to achieve this logic.
Thanks in advance,
Pavan kumar D

Answer 1

You need to add some counters and keep track of last iteration using and index file.
Then make sure that you start reading the file where you was interrupted using select -Skip
<#
.NOTE
The file index.txt is created at the first run and is used to store
the last line accessed of the file to process.
The index read from index.txt is used to skip by already processed
lines at the start of the foreach.
If the index doesn't need to be stored between session, then use
a $global.index instead to speed up the script, instead of an index
file (or a RAM-drive, not very common any more).
At each succefull iteration, the index is incremented and then stored in
index.txt.
When starting the stored index.txt is compared with the numbers of
lines in the file and will through an error if it's passed End Of File.
Make sure to **clear** the index.txt before starting the file process
fresh.
#>
#initialize counters
[int]$StartLine = Get-Content .\index.txt -ErrorAction SilentlyContinue
if (-not $StartLine){[int]$StartLine = 0} # First run will have no index file
$Index = $StartLine
[int]$LastLineOfFile = (get-content 1.txt).count - 1 # Arrays starts at 0
if ($Index -gt $LastLineOfFile){# Don't start if index passed EOF at last run
Write-Error "Index passed end of file"
return
}
foreach ($var in (Get-Content 1.txt | Select -Skip $StartLine)){
"New loop: $Index" | Out-Host # will start empty
"Processing value: $var" | Out-Host
####
# Processing here
####
"Done processing value: $var" | Out-Host
$Index++
$Index > index.txt
"Index incremented" | Out-Host
}
For a good article of using RAM drive, see, i.e. How to Create RAM Disk in Windows 10 for Super-Fast Read and Write Speeds
Windows Server do support RAM disks natively (kind of) by using the iSCSI Target Server.
See, How to Create a RAM Disk on Windows Server?