I made a simple script for this, perhaps you can edit it for your case. Just save it as baverage.sh, then run it as ./baverage.sh your.pdb.
#!/bin/bash echo "----------------------------------" grep '^ATOM' $1|cut -b61-66|cat |awk '{sum+=$1} END { print " Protein Average B =",sum/NR;print " Protein Atom Number =", NR}' grep '^HETATM' $1|grep -v 'HOH'|cut -b61-66 |cat|awk '{sum+=$1} END {print " Ligand/Ion Average B =",sum/NR;print "Ligand/Ion Atom Number =", NR}' grep '^HETATM' $1|grep 'HOH'|cut -b61-66|cat |awk '{sum+=$1} END {print " Water Average B =",sum/NR;print " Water Number =", NR}' echo "----------------------------------" - best, xiaopeng