Distinguish between error and “success” in scanimage-batch

Question

I'm running a little script with the scanimage batch-command on a remote server and would like to know if and how the scan has been done the batch. Therefore the script requires a proper "error"-description to handle the next steps.

Yet scanimage does return a pretty odd message:

scanimage: sane_start: Document feeder out of documents

So the whole output looks like this if there was a success:

scanscript "scanimage --device='brother4:net1;dev0' --format tiff --resolution=150 --source 'Automatic Document Feeder(left aligned,Duplex)' -l 0mm -t 0mm -x210mm -y297mm --batch=$(date +%Y%m%d_%H%M%S)_p%04d.tiff" "/home/qohelet/scans/images/281/" "myscan"
scanimage: rounded value of br-x from 210 to 209.981
scanimage: rounded value of br-y from 297 to 296.973
Scanning -1 pages, incrementing by 1, numbering from 1
Scanning page 1
Scanned page 1. (scanner status = 5)
Scanning page 2
Scanned page 2. (scanner status = 5)
Scanning page 3
scanimage: sane_start: Document feeder out of documents

Technically this is correct, yes - but this happens always when the job is done. In case I haven't put any paper into the feeder it looks like that:

scanscript "scanimage --device='brother4:net1;dev0' --format tiff --resolution=150 --source 'Automatic Document Feeder(left aligned,Duplex)' -l 0mm -t 0mm -x210mm -y297mm --batch=$(date +%Y%m%d_%H%M%S)_p%04d.tiff" "/home/qohelet/scans/images/281/" "myscan"
scanimage: rounded value of br-x from 210 to 209.981
scanimage: rounded value of br-y from 297 to 296.973
Scanning -1 pages, incrementing by 1, numbering from 1
Scanning page 1
scanimage: sane_read: Error during device I/O
Scanned page 1. (scanner status = 9)

The error 9 is unfortunately just one part of the output. How can I distinguish whether it was thrown or not?

In my scanscript I use if to evaluate whether or not the scan was successful:

if eval $1; then
    #Do stuff
else
    #Do error stuff and exit with error code
fi

Unfortunately when using scanimage with a batch it's always counted as a failure. Is there a way to find out what actually happened?

Seems someone had a similar issue with a different scanner (I have a Brother-Scanner, but that's not really related to the issue) already: http://sane.10972.n7.nabble.com/Issue-with-Fujitsu-ScanSnap-iX500-td18589.html

But the topic was not continued there, yet now I'm stuck here and would like to know what to do.