shrc: provide an alias for number of CPUs online

dotfiles/shrc

@@ -40,6 +40,10 @@ if [ -d ~/local/libdata/perl5/site_perl ]; then
 	export PERL5LIB
 fi
 
+if [ -x /sbin/sysctl ] && /sbin/sysctl -n hw.ncpuonline >/dev/null 2>&1; then
+	alias ncpu="/sbin/sysctl -n hw.ncpuonline"
+fi
+
 PS1=
 
 case $SHELL in