Good demo of how to use variables in an awk expression

awk-print-memory-usage.rc.md

Print Memory Usage with Awk

Good demo of how to use variables in an awk expression

Memory Usage as a percentage

memused()  
{
    free -b | awk '/Mem/{ total=2; available=NF; print "MemoryUse:",(100.0*(total/available))"%"; }'; 
};

Memory Available as a percentage

memavail() 
{    
    free -b | awk '/Mem/{ total=2; available=NF; print "MemoryAvail:",(100.0*(1.0-(total/available)))"%"; }'; 
};