[請教] Linux UMASK setting 問題

請問哩句點解？
"`id -gn`" = "`id -un`" -a `id -u` -gt 99

係哩度裡面搵到...
# /etc/bashrc

# System wide functions and aliases
# Environment stuff goes in /etc/profile

# by default, we want this to get set.
# Even for non-interactive, non-login shells.
if [ "`id -gn`" = "`id -un`" -a `id -u` -gt 99 ]; then
        umask 002
else
        umask 022
fi