sh -c "/usr/bin/time perl -e '$|=1; print getlogin(), chr(10)'          - prints username
sh -c "/usr/bin/time perl -e '$|=1; print getlogin(), chr(10)' & wait"  - prints nothing - that is
sh -c "/usr/bin/time perl -e '$|=1; print \$ENV{USER}, chr(10)' & wait" - prints username