diff --git a/.README.md b/.README.md
index c98efa9..72061ed 100644
--- a/.README.md
+++ b/.README.md
@@ -401,6 +401,9 @@ Please note that colors depend on Terminal Emulator and may vary based on its se
 |yellow|`\033[0;33m`|
 |yellow (bold)|`\033[1;33m`|
 
+## Convert.
+`convert <FROM.gz> <TO.xz>`|Convert between different formats.
+
 ## Copy/paste.
 
 Command|Description
@@ -458,13 +461,6 @@ Command|Description
 `dcpu [SERVICE]`|Update and recreate a compose service.
 `dcul [SERVICE]`|Start a compose service and show its logs.
 
-## Pack.
-
-Command|Description
----|---
-`pack <TARGET.ext> <FILES>`|Create desired file format from other files.
-`unpack [FILES]`|Attempt to extract file content.
-
 ## Environment variables.
 
 Variable|Description
@@ -569,6 +565,13 @@ Command|Description
 ---|---
 `own [USER] [FILE]`|Change ownership & permissions to specified user. Ownership changes only when root.
 
+## Pack.
+
+Command|Description
+---|---
+`pack <TARGET.ext> <FILES>`|Create desired file format from other files.
+`unpack [FILES]`|Attempt to extract file content.
+
 ## Permissions.
 
 Command|Description
@@ -583,11 +586,18 @@ Command|Description
 `ps <PROGRAM>`|Show process info for matching [PROGRAM] name.
 
 ## Recursive.
+
 Command|Description
 ---|---
 `recursive <COMMAND>`|Cd into every directory recursively and run specified command in each dir.
 `recursive1 <COMMAND>`|Cd into every directory in current directory and run specified command in each dir.
 
+## Rust.
+
+Command|Description
+---|---
+`rust_book`|Open Rust book in a browser.
+
 ## Shopt.
 
 Shopt|Description
diff --git a/.config/bash/module/archive.sh b/.config/bash/module/archive.sh
index ef5664f..e71e235 100644
--- a/.config/bash/module/archive.sh
+++ b/.config/bash/module/archive.sh
@@ -117,12 +117,10 @@ archive_check()
   done
 
   # report result.
-  if [[ ${count} -gt 1 ]] || [[ "${*}" = "" ]]; then
-    if [[ ${failed} -gt 0 ]]; then
-      echo -e "${color_bred}Items failed to validate: ${failed}.${color_default}"
-    else
-      echo -e "${color_green}All successful.${color_default}"
-    fi
+  if [[ ${failed} -gt 0 ]]; then
+    echo -e "${color_bred}Items failed to validate: ${failed}.${color_default}"
+  else
+    echo -e "${color_green}All successful.${color_default}"
   fi
 }
 
diff --git a/.config/bash/module/convert.sh b/.config/bash/module/convert.sh
new file mode 100644
index 0000000..13cc51f
--- /dev/null
+++ b/.config/bash/module/convert.sh
@@ -0,0 +1,51 @@
+# Convert between different formats.
+# Usage: convert <FROM.gz> <TO.xz>
+convert() {
+  local input="${1}"
+  local output="${2}"
+  local from="${input##*.}"
+  local to="${output##*.}"
+
+  # Report no output.
+  if [[ "${to}" = "" ]]; then
+    echo -e "${color_bred}no output file/format.${color_default}"
+    return 1
+  fi
+
+  # Report no input.
+  if [[ "${from}" = "" ]]; then
+    echo -e "${color_bred}no input file/format.${color_default}"
+    return 2
+  fi
+
+  # Process.
+  case "${from}-${to}" in
+    "gz-xz"|"tgz-txz")
+      _convert_gz-xz "${input}" "${output}"
+      ;;
+    "xz-gz"|"txz-tgz")
+      _convert_xz-gz "${input}" "${output}"
+      ;;
+    *)
+      echo -e "${color_yellow}Conversion ${from}-${to} not supported.${color_default}"
+      return 3
+      ;;
+  esac
+
+  if [[ $? = 0 ]]; then
+    echo -e "${color_green}Done.${color_default}"
+  else
+    echo -e "${color_bred}There were errors.${color_default}"
+  fi
+}
+
+_convert_gz-xz() {
+  pv "${1}" | gzip -d | xz -9e > "${2}"
+}
+
+_convert_xz-gz() {
+  pv "${1}" | xz -d | gzip -1 > "${2}"
+}
+
+# Export.
+export -f convert _convert_gz-xz _convert_xz-gz