Not that it was very accurate to begin with, but...
The command
/usr/bin/free -b | awk '/Mem:|cache:/ {print $2,$3}' | sed 'N;s/\n/ /' | awk '{print ($4*100)/$1}'
no longer works on CentOS, assuming Fedora as well.
The buffers and cache was removed on procps-ng-3.3.10
How can I get Memory Utilization from RH systems where SNMP is not an option?