diff --git a/cert-expirations.sh b/cert-expirations.sh
index b9f294e..9dba20b 100644
--- a/cert-expirations.sh
+++ b/cert-expirations.sh
@@ -1,72 +1,124 @@
 #!/bin/sh
 
-SYSTEM=$(uname | tr '[:upper:]' '[:lower:]')
+VERSION="22.04"
 
-if [ "${SYSTEM}" = "openbsd" ]; then
-    carp=$(/sbin/ifconfig carp0 2>/dev/null | grep 'status' | cut -d' ' -f2)
-    
-    if [ "$carp" = "backup" ]; then
-        exit 0
-    fi
-fi
+show_version() {
+    cat <<END
+cert-expirations.sh version ${VERSION}
 
-cacert_path="/etc/openvpn/ssl/ca/cacert.pem"
-index_path="/etc/openvpn/ssl/ca/index.txt"
-somedays="3456000" # 40 days currently
-expired_certs=""
-expiring_soon_certs=""
-still_valid_certs=""
+Copyright 2020-2022 Evolix <info@evolix.fr>,
+                    Jérémy Lecour <jlecour@evolix.fr>,
+                    Jérémy Dubois <jdubois@evolix.fr>
+                    and others.
 
-echo "Warning : all times are in UTC !"
-echo ""
-echo "CA certificate:"
-openssl x509 -enddate -noout -in ${cacert_path} \
-    | cut -d '=' -f 2 \
-    | sed -e "s/^\(.*\)\ \(20..\).*/- \2 \1/"
-
-echo ""
-
-# Syntax "cmd | { while read line; do var="foo"; done echo $var }" needed, otherwise $var is empty at the end of while loop
-grep ^V ${index_path} \
-    | awk -F "/" '{print $1,$5}' \
-    | awk '{print $2,$5}' \
-    | sed 's/CN=//' \
-    | sed -E 's/([[:digit:]]{2})([[:digit:]]{2})([[:digit:]]{2})([[:digit:]]{2})([[:digit:]]{2})([[:digit:]]{2})Z (.*)/- 20\1 \2 \3 \4:\5:\6 \7/' \
-    | awk '{if ($3 == "01") $3="Jan"; else if ($3 == "02") $3="Feb"; else if ($3 == "03") $3="Mar"; else if ($3 == "04") $3="Apr"; else if ($3 == "05") $3="May"; else if ($3 == "06") $3="Jun"; else if ($3 == "07") $3="Jul"; else if ($3 == "08") $3="Aug"; else if ($3 == "09") $3="Sep"; else if ($3 == "10") $3="Oct"; else if ($3 == "11") $3="Nov"; else if ($3 == "12") $3="Dec"; print $0;}' \
-    | sort -n -k 2 -k 3M -k 4 | { 
-        while read -r line; do
-
-        # Predicting expirations - OpenBSD case (date is not the same than in Linux)
-        if [ "${SYSTEM}" = "openbsd" ]; then
-            # Already expired if expiration date is before now
-            if [ "$(TZ=:Zulu date -jf "%Y %b %d %H:%M:%S" "$(echo "$line" | awk '{print $2,$3,$4,$5}')" +%s)" -le "$(date +%s)" ]; then
-                expired_certs="${expired_certs}$line\n"
-            # Expiring soon if expiration date is after now and before now + $somedays days
-            elif [ "$(TZ=:Zulu date -jf "%Y %b %d %H:%M:%S" "$(echo "$line" | awk '{print $2,$3,$4,$5}')" +%s)" -gt "$(date +%s)" ] && [ "$(TZ=:Zulu date -jf "%Y %b %d %H:%M:%S" "$(echo "$line" | awk '{print $2,$3,$4,$5}')" +%s)" -lt "$(($(date +%s) + somedays))" ]; then
-                expiring_soon_certs="${expiring_soon_certs}$line\n"
-            # Still valid for a time if expiration date is after now + $somedays days
-            elif [ "$(TZ=:Zulu date -jf "%Y %b %d %H:%M:%S" "$(echo "$line" | awk '{print $2,$3,$4,$5}')" +%s)" -ge "$(($(date +%s) + somedays))" ]; then
-                still_valid_certs="${still_valid_certs}$line\n"
-            fi
-        # Non OpenBSD cases
-        else
-            # Already expired if expiration date is before now
-            if [ "$(TZ=:Zulu date -d "$(echo "$line" | awk '{print $3,$4,$2,$5}')" +%s)" -le "$(date +%s)" ]; then
-                expired_certs="${expired_certs}$line\n"
-            # Expiring soon if expiration date is after now and before now + $somedays days
-            elif [ "$(TZ=:Zulu date -d "$(echo "$line" | awk '{print $3,$4,$2,$5}')" +%s)" -gt "$(date +%s)" ] && [ "$(TZ=:Zulu date -d "$(echo "$line" | awk '{print $3,$4,$2,$5}')" +%s)" -lt "$(($(date +%s) + somedays))" ]; then
-                expiring_soon_certs="${expiring_soon_certs}$line\n"
-            # Still valid for a time if expiration date is after now + $somedays days
-            elif [ "$(TZ=:Zulu date -d "$(echo "$line" | awk '{print $3,$4,$2,$5}')" +%s)" -ge "$(($(date +%s) + somedays))" ]; then
-                still_valid_certs="${still_valid_certs}$line\n"
-            fi
-        fi
-    done
-    
-    echo "Expired client certificates:"
-    echo "${expired_certs}"
-    echo "Valid client certificates expiring soon (in less than $((somedays / 60 / 60 / 24)) days):"
-    echo "${expiring_soon_certs}"
-    echo "Valid client certificates expiring later (in more than $((somedays / 60 / 60 / 24)) days):"
-    echo "${still_valid_certs}"
+cert-expirations.sh comes with ABSOLUTELY NO WARRANTY.  This is free software,
+and you are welcome to redistribute it under certain conditions.
+See the MIT Licence for details.
+END
 }
+
+show_usage() {
+    cat <<END
+Usage: ${0} [--version]
+END
+}
+
+check_ca_expiration() {
+    echo "CA certificate:"
+    openssl x509 -enddate -noout -in ${cacert_path} \
+        | cut -d '=' -f 2 \
+        | sed -e "s/^\(.*\)\ \(20..\).*/- \2 \1/"
+}
+
+check_certs_expiration() {
+    # Syntax "cmd | { while read line; do var="foo"; done echo $var }" needed, otherwise $var is empty at the end of while loop
+    grep ^V ${index_path} \
+        | awk -F "/" '{print $1,$5}' \
+        | awk '{print $2,$5}' \
+        | sed 's/CN=//' \
+        | sed -E 's/([[:digit:]]{2})([[:digit:]]{2})([[:digit:]]{2})([[:digit:]]{2})([[:digit:]]{2})([[:digit:]]{2})Z (.*)/- 20\1 \2 \3 \4:\5:\6 \7/' \
+        | awk '{if ($3 == "01") $3="Jan"; else if ($3 == "02") $3="Feb"; else if ($3 == "03") $3="Mar"; else if ($3 == "04") $3="Apr"; else if ($3 == "05") $3="May"; else if ($3 == "06") $3="Jun"; else if ($3 == "07") $3="Jul"; else if ($3 == "08") $3="Aug"; else if ($3 == "09") $3="Sep"; else if ($3 == "10") $3="Oct"; else if ($3 == "11") $3="Nov"; else if ($3 == "12") $3="Dec"; print $0;}' \
+        | sort -n -k 2 -k 3M -k 4 | { 
+            while read -r line; do
+    
+            # Predicting expirations - OpenBSD case (date is not the same than in Linux)
+            if [ "${SYSTEM}" = "openbsd" ]; then
+                # Already expired if expiration date is before now
+                if [ "$(TZ=:Zulu date -jf "%Y %b %d %H:%M:%S" "$(echo "$line" | awk '{print $2,$3,$4,$5}')" +%s)" -le "$(date +%s)" ]; then
+                    expired_certs="${expired_certs}$line\n"
+                # Expiring soon if expiration date is after now and before now + $somedays days
+                elif [ "$(TZ=:Zulu date -jf "%Y %b %d %H:%M:%S" "$(echo "$line" | awk '{print $2,$3,$4,$5}')" +%s)" -gt "$(date +%s)" ] && [ "$(TZ=:Zulu date -jf "%Y %b %d %H:%M:%S" "$(echo "$line" | awk '{print $2,$3,$4,$5}')" +%s)" -lt "$(($(date +%s) + somedays))" ]; then
+                    expiring_soon_certs="${expiring_soon_certs}$line\n"
+                # Still valid for a time if expiration date is after now + $somedays days
+                elif [ "$(TZ=:Zulu date -jf "%Y %b %d %H:%M:%S" "$(echo "$line" | awk '{print $2,$3,$4,$5}')" +%s)" -ge "$(($(date +%s) + somedays))" ]; then
+                    still_valid_certs="${still_valid_certs}$line\n"
+                fi
+            # Non OpenBSD cases
+            else
+                # Already expired if expiration date is before now
+                if [ "$(TZ=:Zulu date -d "$(echo "$line" | awk '{print $3,$4,$2,$5}')" +%s)" -le "$(date +%s)" ]; then
+                    expired_certs="${expired_certs}$line\n"
+                # Expiring soon if expiration date is after now and before now + $somedays days
+                elif [ "$(TZ=:Zulu date -d "$(echo "$line" | awk '{print $3,$4,$2,$5}')" +%s)" -gt "$(date +%s)" ] && [ "$(TZ=:Zulu date -d "$(echo "$line" | awk '{print $3,$4,$2,$5}')" +%s)" -lt "$(($(date +%s) + somedays))" ]; then
+                    expiring_soon_certs="${expiring_soon_certs}$line\n"
+                # Still valid for a time if expiration date is after now + $somedays days
+                elif [ "$(TZ=:Zulu date -d "$(echo "$line" | awk '{print $3,$4,$2,$5}')" +%s)" -ge "$(($(date +%s) + somedays))" ]; then
+                    still_valid_certs="${still_valid_certs}$line\n"
+                fi
+            fi
+        done
+        
+        echo "Expired client certificates:"
+        echo "${expired_certs}"
+        echo "Valid client certificates expiring soon (in less than $((somedays / 60 / 60 / 24)) days):"
+        echo "${expiring_soon_certs}"
+        echo "Valid client certificates expiring later (in more than $((somedays / 60 / 60 / 24)) days):"
+        echo "${still_valid_certs}"
+    }
+}
+
+main() {
+    SYSTEM=$(uname | tr '[:upper:]' '[:lower:]')
+    
+    if [ "${SYSTEM}" = "openbsd" ]; then
+        carp=$(/sbin/ifconfig carp0 2>/dev/null | grep 'status' | cut -d' ' -f2)
+    
+        if [ "$carp" = "backup" ]; then
+            exit 0
+        fi
+    fi
+    
+    cacert_path="/etc/openvpn/ssl/ca/cacert.pem"
+    index_path="/etc/openvpn/ssl/ca/index.txt"
+    somedays="3456000" # 40 days currently
+    expired_certs=""
+    expiring_soon_certs=""
+    still_valid_certs=""
+
+    case "$1" in
+        version|--version)
+            show_version
+            exit 0
+        ;;
+
+        help|--help)
+            show_usage
+            exit 0
+        ;;
+
+        "")
+            echo "Warning : all times are in UTC !"
+            echo ""
+            check_ca_expiration
+            echo ""
+            check_certs_expiration
+        ;;
+
+        *)
+            show_usage >&2
+            exit 1
+        ;;
+    esac
+}
+
+main "$@"