ifonline

   1 #!/bin/sh
   2
   3 set -e
   4
   5 usage() {
   6   cat << EOF
   7 Executes a given command if there is an internet connection. Availability of an
   8 connection is tested by (i) the availability of a default route and (ii) the
   9 pingability of a test host.
  10
  11 Usage:
  12  $0 [OPTIONS]
  13  $0 -h
  14  $0 -c "echo 'online'"
  15
  16 OPTIONS:
  17   -h            Show this text
  18   -v            Verbose output
  19   -p HOST       Host for ping test. Default: 8.8.8.8
  20   -c CMD        Command to execute if online
  21 EOF
  22 }
  23
  24 CMD=""
  25 VERBOSE=0
  26 PINGHOST="8.8.8.8"
  27
  28 while getopts "hvc:p:" OPTION; do
  29
  30   case "${OPTION}" in
  31     h)
  32       usage
  33       exit
  34       ;;
  35     v)
  36       VERBOSE=1
  37       ;;
  38     p)
  39       PINGHOST=${OPTARG}
  40       ;;
  41     c)
  42       CMD=${OPTARG}
  43       ;;
  44   esac
  45 done
  46
  47 if [ -z "${CMD}" ]; then
  48     echo "No command given."
  49     usage
  50     exit 2
  51 fi
  52
  53 if [ -z "$(ip r list exact default)" ]; then
  54   if [ "1" -eq "${VERBOSE}" ];  then
  55     echo "Not online because no default route."
  56   fi
  57   exit
  58 fi
  59
  60
  61 if ! ping -c1 "${PINGHOST}" 2>&1 >/dev/null; then
  62   if [ "1" -eq "${VERBOSE}" ];  then
  63     echo "Not online because cannot ping ${PINGHOST}."
  64   fi
  65   exit
  66 fi
  67
  68 ${CMD}