#! /bin/sh

# set -x

dirs="/bin /usr/bin /sbin /usr/sbin /etc"
NETSTAT=`find ${dirs} -follow -name netstat -type f -print 2>/dev/null |
   head -n 1`
IFCONFIG=`find ${dirs} -follow -name ifconfig -type f -print 2>/dev/null |
   head -n 1`

if [ $# -gt 0 ] ; then
   if expr "${1}" + 0 2>&1 | grep non-numeric > /dev/null
   then
      echo "`basename ${0}`: non-numeric argument"
      exit 1
   fi
fi

# Default interval is 10 seconds.
interval=${1-10}

# Get list of network interfaces if none was specified.
ifaces=${2-`${NETSTAT} -in |
      grep "[0-9]" |
      cut -f1 -d" " |
      grep -v :`}
ifaces=${2-`${IFCONFIG} -a |
      grep : |
      grep -v '^ ' |
      sed 's/:* .*$//'`}

# See if `ifconfig' reports bytes.
if ${IFCONFIG} `echo ${ifaces} | cut -d" " -f1` | grep -i bytes > /dev/null
then
   unit=bytes
else
   unit=packets
fi

# Digits subexpression for `sed'
digits='\([0-9][0-9]*\)'

case ${unit} in
   bytes)
      tab='	'
      txrx() {
         ${IFCONFIG} "${1}" |
            grep bytes: |
sed "s/[${tab} ]*RX bytes:${digits}.*TX bytes:${digits}.*/RX=\1 TX=\2/"
      }
      ;;

   packets)
      field() {
         fieldname=${1}
         val=0
         set -f `${NETSTAT} -i | grep Name`
         while [ ! -z "${1}" ]
         do
            val=`expr ${val} + 1`
            if [ "${1}" = "${fieldname}" ]
            then
               break
            fi
            shift
         done
         echo ${val}
      }
      
      in=`field Ipkts`
      out=`field Opkts`
      unset field
      txrx() {
         ${NETSTAT} -in |
            grep "${1}" |
            sed "s/  */ /g" |
            cut -d" " -f${in},${out} |
            sed "s/^${digits}  *${digits}.*$/RX=\1 TX=\2/"
      }
      ;;
esac

# Initialize trap
for iface in ${ifaces}
do
   trap="${trap}
"
done

# So when we exit (via Ctrl-C), it leaves all the numbers up.
trap "exit" 1 2 3
trap "printf \"${trap}\"" 0

# Cursor up 1 motion.
cuu1=`tput cuu1`
# Erase 1 line.
el=`tput el`

total_time=0

# Start a timer.
sleep ${interval} &


while :
do
   for iface in ${ifaces}
   do
      iface_nm=`echo ${iface} | sed 's/:/_/'`
      eval `txrx ${iface}`

      # Get current count
      eval `echo TXC_${iface_nm}=${TX}`
      eval `echo RXC_${iface_nm}=${RX}`

      # Calculate data this interval.
      eval `
         echo 'TXD_'${iface_nm}'=\`
            expr ${TXC_'${iface_nm}'} - ${TXP_'${iface_nm}'} 2>/dev/null
         \`'
      `
      eval `
         echo 'RXD_'${iface_nm}'=\`
            expr ${RXC_'${iface_nm}'} - ${RXP_'${iface_nm}'} 2>/dev/null
         \`'
      `

      # Calculate total data.
      eval `
         echo 'TXT_'${iface_nm}'=\`
            expr ${TXT_'${iface_nm}'-0} + ${TXD_'${iface_nm}':-0}
         \`'
      `
      eval `
         echo 'RXT_'${iface_nm}'=\`
            expr ${RXT_'${iface_nm}'-0} + ${RXD_'${iface_nm}':-0}
         \`'
      `

      # Calculate current data rate (bandwidth).
      eval `
         echo 'TXB_'${iface_nm}'=\`
            expr ${TXD_'${iface_nm}':-0} / ${interval}
         \`'
      `
      eval `
         echo 'RXB_'${iface_nm}'=\`
            expr ${RXD_'${iface_nm}':-0} / ${interval}
         \`'
      `

      # Calculate average data rate.
      eval `
         echo 'TXA_'${iface_nm}'=\`
            expr ${TXT_'${iface_nm}'} / ${total_time} 2>/dev/null
         \`'
      `
      eval `
         echo 'RXA_'${iface_nm}'=\`
            expr ${RXT_'${iface_nm}'} / ${total_time} 2>/dev/null
         \`'
      `

      # Set new max bandwidth if reached.
      if eval [ `
         echo '"${TXM_'${iface_nm}'--1}" -lt "${TXB_'${iface_nm}'-0}"'
      ` ]
      then
         eval `echo 'TXM_'${iface_nm}'=${TXB_'${iface_nm}'-0}'`
      fi
      if eval [ `
         echo '"${RXM_'${iface_nm}'--1}" -lt "${RXB_'${iface_nm}'-0}"'
      ` ]
      then
         eval `echo 'RXM_'${iface_nm}'=${RXB_'${iface_nm}'-0}'`
      fi

      # Print the result.
      eval `echo printf \
'"%s%6s: TX=%s (%s max, %s avg) RX=%s (%s max, %s avg) ${unit}/sec"' \
            "${el}" \
            "${iface}"' \
            "${TXB_'${iface_nm}'}" \
            "${TXM_'${iface_nm}'}" \
            "${TXA_'${iface_nm}'}" \
            "${RXB_'${iface_nm}'}" \
            "${RXM_'${iface_nm}'}" \
            "${RXA_'${iface_nm}'}"'`
      echo

      # Set the current to previous.
      eval `echo 'TXP_'${iface_nm}'=${TXC_'${iface_nm}'}'`
      eval `echo 'RXP_'${iface_nm}'=${RXC_'${iface_nm}'}'`
   done

   # Move the cursor back up to the beginning.
   for iface in ${ifaces}
   do
      printf "%s\r" ${cuu1}
   done

   # Increment total time.
   total_time=`expr ${total_time} + ${interval}`

   # Wait for the timer to complete.
   wait

   # Start the next timer.
   sleep ${interval} &
done