memory: freebsd support

pfetch

@@ -212,7 +212,7 @@ get_host() {
             host="$name $version $model"
         ;;
 
-        Darwin*)
+        Darwin*|FreeBSD*)
             host=$(sysctl -n hw.model)
         ;;
 
@@ -401,8 +401,6 @@ get_memory() {
         ;;
 
         OpenBSD*)
-            # If you run OpenBSD and can send me the full output of
-            # 'vm_stat' I'll be able to add full support here.
             mem_full=$(($(sysctl -n hw.physmem) / 1024 / 1024))
 
             # This is a really simpler parser for 'vmstat' which grabs
@@ -426,10 +424,31 @@ get_memory() {
 			EOF
         ;;
 
+        # Used memory is calculated using the following "formula" (FreeBSD):
+        # (inactive_count + free_count + cache_count) * page_size / 1024
         FreeBSD*)
-            # If you run FreeBSD and can help me get
-            # the used memory amount, I'll be able to add support here.
             mem_full=$(($(sysctl -n hw.physmem) / 1024 / 1024))
+
+            # Use 'set --' to store the output of the command in the
+            # argument list. POSIX sh has no arrays but this is close enough.
+            #
+            # Disable the shellcheck warning for word-splitting
+            # as it's safe and intended ('set -f' disables globbing).
+            # shellcheck disable=2046
+            {
+                set -f
+                set +f -- $(sysctl -n hw.pagesize \
+                                      vm.stats.vm.v_inactive_count \
+                                      vm.stats.vm.v_free_count \
+                                      vm.stats.vm.v_cache_count)
+            }
+
+            # Calculate the amount of free memory.
+            # $1: hw.pagesize
+            # $2: vm.stats.vm.v_inactive_count
+            # $3: vm.stats.vm.v_free_count
+            # $4: vm.stats.vm.v_cache_count
+            mem_free=$((($2 + $3 + $4) * $1 / 1024 / 1024))
         ;;
 
         NetBSD*)