sed '{s/./*/2;s/./*/3;s/./*/4;s/./*/5;s/./*/6;}' urfile
sed '/^../{h;s/^.\(.\{1,5\}\).*/\1/;s/./*/g;G;s/\(.*\)\n\(.\).\{1,5\}\(.*\)/\2\1\3/;}' urfile
sed '
:a
/^.[*]\{5\}/!{
s/\(.[*]*\)./\1*/
/*$/!ta
}' urfile
awk '{a=(substr($0,2,5));gsub(/./,"*",a);print substr($0,1,1)a""substr($0,7,length($0))}' urfile
awk '{for(i=1;i<=length($0);i++) if(i>1&&i<6) printf "*";else printf substr($0,i,1);print ""}' urfile