Comment 32 for bug 68267

was said earlier:
 1) That "set +e ... set -e" seems -really- bogus.
       That forces exit on non-zero exit status from
       simple commands, and this script intentionally
       invokes some simple commands that might exit
       non-zero, such as the expr line on the very next
       line after the "set +e".
$ help set
"-e Exit immediately if a command exits with a non-zero status."
"Using + rather than - causes these flags to be turned off."
So as I understand: "set +e" make sure that it will NOT exit
script because of the non-zero expr results. Which seems ok.