Suppress output of popd and implement the help text.

ddos-mitigator/superscript.sh

@@ -47,8 +47,42 @@ blue="\033[38;2;0;85;255m"
 bold="\033[1m"
 reset="\033[0m"
 
+# Clean up when the script exits.
+trap 'sudo -k; popd >/dev/null; rm -r ${tmpdir}' EXIT
+
+# Create a temp directory, chdir into it and create the (initially empty)
+# banlist file.
+tmpdir=$(mktemp -d)
+# Suppress output of dir stack.
+pushd "${tmpdir}" > /dev/null
+touch "${banlist}"
+
 function printHelp() {
-	echo "Help ... to be written."
+	cat <<ENDOFHELP
+Usage: $(basename $0) [OPTION...]
+
+  -a, --auto[=LIMIT]  Enable the autopilot for automatically banning chinese IP
+                      addresses (whois output must contain "source: APNIC" and
+                      "country: CN").
+                      When LIMIT is given, only auto-ban IP addresses with at
+                      least LIMIT current connections.
+                      When LIMIT is omitted, assume LIMIT=1.
+
+  -n, --netmask=SIZE  SIZE defines the subnet size in bytes to be analyzed.
+                      Valid values are:
+                      - 1 or 8 for class A networks (X.0.0.0/8)
+                      - 2 or 16 for class B networks (X.X.0.0/16)
+                      - 3 or 24 for class C networks (X.X.X.0/24)
+                      - 4 or 32 for class D networks (X.X.X.X/32)
+
+  -h, --help          Show this help message
+
+Mandatory or optional arguments to long options are also mandatory or optional
+for any corresponding short options.
+
+When invoked without options, the autopilot is disabled and the netmask SIZE is
+inquired interactively.
+ENDOFHELP
 }
 
 function parseCommandline() {
@@ -117,16 +151,6 @@ function parseCommandline() {
 	done
 }
 
-# Clean up when the script exits.
-trap 'sudo -k; popd; rm -r ${tmpdir}' EXIT
-
-# Create a temp directory, chdir into it and create the (initially empty)
-# banlist file.
-tmpdir=$(mktemp -d)
-# Suppress output of dir stack.
-pushd "${tmpdir}" > /dev/null
-touch "${banlist}"
-
 # Parse the command line options
 autopilot=0
 netmask=0