Convert repeated code into a loop

Question

I have a router running DD-WRT that has a start up script used to wake my computer on LAN requests on certain ports. I found this shell script here and changed it to allow for wake on multiple ports. I tried doing a for loop so I wouldn't have to repeat any code, but that didn't work. That only thing that worked was:

#!/bin/sh
#Enable JFFS2 and place script in /jffs/ then run on startup in web interface.
#You can check the log from http://192.168.1.1/user/wol.html
INTERVAL=1
PINGTIME=1
OLD=""
PORTPLEX=32400
PORTFTPCTRL=20
PORTFTPDATA=21
PORTRDP=3389
WOLPORT=9
TARGET=192.168.1.8
BROADCAST=192.168.1.255
MAC=aa:bb:cc:dd:ee:ff
WOL=/usr/sbin/wol
LOGFILE="/tmp/www/wol.html"
echo "<meta http-equiv=\"refresh\" content=\"10\">" > $LOGFILE
echo "["`date`"] AUTO WOL Script started. <br>" >> $LOGFILE

while sleep $INTERVAL;do

NEW=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTPLEX"'/ {print }' | tail -1`
SRC=`dmesg | awk -F'[=| ]' '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTPLEX"'/ {print $7}' | tail -1`
LINE=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTPLEX"'/'`
if [ "$NEW" != "" -a "$NEW" != "$OLD" ]; then
   if ping -qw $PINGTIME $TARGET >/dev/null; then
      echo "NOWAKE $TARGET was accessed by $SRC and is already alive at" `date` "<br>">> $LOGFILE
   else
      echo "WAKE $SRC causes wake on lan at" `date` "<br>">> $LOGFILE
      $WOL -i $BROADCAST -p $WOLPORT $MAC >> $LOGFILE
      echo "<br>" >> $LOGFILE
      sleep 1
   fi
   OLD=$NEW
fi

NEW=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTFTPCTRL"'/ {print }' | tail -1`
SRC=`dmesg | awk -F'[=| ]' '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTFTPCTRL"'/ {print $7}' | tail -1`
LINE=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTFTPCTRL"'/'`
if [ "$NEW" != "" -a "$NEW" != "$OLD" ]; then
   if ping -qw $PINGTIME $TARGET >/dev/null; then
      echo "NOWAKE $TARGET was accessed by $SRC and is already alive at" `date` "<br>">> $LOGFILE
   else
      echo "WAKE $SRC causes wake on lan at" `date` "<br>">> $LOGFILE
      $WOL -i $BROADCAST -p $WOLPORT $MAC >> $LOGFILE
      echo "<br>" >> $LOGFILE
      sleep 1
   fi
   OLD=$NEW
fi

NEW=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTFTPDATA"'/ {print }' | tail -1`
SRC=`dmesg | awk -F'[=| ]' '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTFTPDATA"'/ {print $7}' | tail -1`
LINE=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTFTPDATA"'/'`
if [ "$NEW" != "" -a "$NEW" != "$OLD" ]; then
   if ping -qw $PINGTIME $TARGET >/dev/null; then
      echo "NOWAKE $TARGET was accessed by $SRC and is already alive at" `date` "<br>">> $LOGFILE
   else
      echo "WAKE $SRC causes wake on lan at" `date` "<br>">> $LOGFILE
      $WOL -i $BROADCAST -p $WOLPORT $MAC >> $LOGFILE
      echo "<br>" >> $LOGFILE
      sleep 1
   fi
   OLD=$NEW
fi

NEW=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTRDP"'/ {print }' | tail -1`
SRC=`dmesg | awk -F'[=| ]' '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTRDP"'/ {print $7}' | tail -1`
LINE=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORTRDP"'/'`
if [ "$NEW" != "" -a "$NEW" != "$OLD" ]; then
   if ping -qw $PINGTIME $TARGET >/dev/null; then
      echo "NOWAKE $TARGET was accessed by $SRC and is already alive at" `date` "<br>">> $LOGFILE
   else
      echo "WAKE $SRC causes wake on lan at" `date` "<br>">> $LOGFILE
      $WOL -i $BROADCAST -p $WOLPORT $MAC >> $LOGFILE
      echo "<br>" >> $LOGFILE
      sleep 1
   fi
   OLD=$NEW
fi

done

I'm guessing either (1) I don't really understand how for-loops work in bash, or (2) DD-WRT's shell scripting is different than other versions of Linux, or both.

How would I convert this portion of code to be executed in a for-loop that loops over each port?

NEW=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORT"'/ {print }' | tail -1`
SRC=`dmesg | awk -F'[=| ]' '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORT"'/ {print $7}' | tail -1`
LINE=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORT"'/'`
if [ "$NEW" != "" -a "$NEW" != "$OLD" ]; then
   if ping -qw $PINGTIME $TARGET >/dev/null; then
      echo "NOWAKE $TARGET was accessed by $SRC and is already alive at" `date` "<br>">> $LOGFILE
   else
      echo "WAKE $SRC causes wake on lan at" `date` "<br>">> $LOGFILE
      $WOL -i $BROADCAST -p $WOLPORT $MAC >> $LOGFILE
      echo "<br>" >> $LOGFILE
      sleep 1
   fi
   OLD=$NEW
fi

Thanks!

Answer 1

Have you tried ? :

for PORT in $PORTPLEX $PORTFTPCTRL $PORTFTPDATA $PORTRDP; do
            NEW=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORT"'/ {print }' | tail -1`
    SRC=`dmesg | awk -F'[=| ]' '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORT"'/ {print $7}' | tail -1`
    LINE=`dmesg | awk '/ACCEPT/ && /DST='"$TARGET"'/ && /DPT='"$PORT"'/'`
    if [ "$NEW" != "" -a "$NEW" != "$OLD" ]; then
       if ping -qw $PINGTIME $TARGET >/dev/null; then
          echo "NOWAKE $TARGET was accessed by $SRC and is already alive at" `date` "<br>">> $LOGFILE
       else
          echo "WAKE $SRC causes wake on lan at" `date` "<br>">> $LOGFILE
          $WOL -i $BROADCAST -p $WOLPORT $MAC >> $LOGFILE
          echo "<br>" >> $LOGFILE
          sleep 1
       fi
       OLD=$NEW
    fi
done