add example

example.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -o errexit
+set -o nounset
+set -o pipefail
+
+if [[ "${1-}" =~ ^-*h(elp)?$ ]]; then
+    echo 'Usage: ./script.sh arg-one arg-two
+This is an awesome bash script to make your life better.
+'
+    exit
+fi
+
+if [[ "${TRACE-0}" == "1" ]]; then
+    set -o xtrace
+fi
+
+cd "$(dirname "$0")"
+
+main() {
+  # no connection
+  state=0
+
+  # test each interfaces for connectivity
+  for iface in $(ls /sys/class/net/ | grep -v lo); do
+    if [[ $(cat /sys/class/net/$iface/carrier 2>/dev/null) = 1 ]]; then
+      echo -e "$iface \e[32mconnected\e[0m"
+      state=1
+    else
+      echo -e "$iface \e[31mno_connection\e[0m"
+    fi
+  done
+
+  # check summary
+  if [[ $state -eq 0 ]]; then
+    echo -e " \n\e[31mno connection\e[0m" > /dev/stderr;
+    exit -1;
+  else
+    echo -e "\n\e[32mconnected\e[0m" > /dev/stdout;
+    exit 0;
+  fi
+}
+
+main "[email protected]"