diff --git a/shellbox b/shellbox
index 2fa41a4..b6e4dc9 100755
--- a/shellbox
+++ b/shellbox
@@ -5,26 +5,21 @@
 
 HOME=/root
 . /etc/profile
+PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
 
-export PATH=$PATH:/usr/local/bin
-
-# AD84: export HOSTNAME=$(hostname -s)
-
-
-# AD84: added
 if [ -f /usr/local/bin/getIocBootEnv ]
 then
         . /usr/local/bin/getIocBootEnv
-	#echo ""
-	#echo "shellbox:  IOC=$IOC"
-	#echo "shellbox:    FACILITY=$FACILITY"
-	#echo "shellbox:    ROOTFSSERVERIP=$ROOTFSSERVERIP"
-	#echo "shellbox:    BOOTPC=$BOOTPC"
-	#echo "shellbox:    CMDLINE_HOST=$CMDLINE_HOST"
-	#echo "shellbox:    CMDLINE_ETH=$CMDLINE_ETH"
-	#echo "shellbox:    BOOTIF_BCAST=$BOOTIF_BCAST"
-	#echo "shellbox:    BOOTIF_IP=$BOOTIF_IP"
-	#echo ""
+        #echo ""
+        #echo "shellbox:  IOC=$IOC"
+        #echo "shellbox:    FACILITY=$FACILITY"
+        #echo "shellbox:    ROOTFSSERVERIP=$ROOTFSSERVERIP"
+        #echo "shellbox:    BOOTPC=$BOOTPC"
+        #echo "shellbox:    CMDLINE_HOST=$CMDLINE_HOST"
+        #echo "shellbox:    CMDLINE_ETH=$CMDLINE_ETH"
+        #echo "shellbox:    BOOTIF_BCAST=$BOOTIF_BCAST"
+        #echo "shellbox:    BOOTIF_IP=$BOOTIF_IP"
+        #echo ""
 fi
 if [ "$IOC" == "" ]
 then
@@ -33,28 +28,39 @@ else
   HOSTNAME=$IOC
 fi
 export HOSTNAME
-# AD84: end added
 
+fail () {
+  echo $@ >&2
+  exit 1
+}
 
-exe=/usr/local/bin/procServ
 options="-k ^X --killsig 15 -x ^D -i ^C --allow -c"
 prog=shellbox
-params=
 conf=/etc/shellbox.conf
 logdir=/var/log/$prog
 shells=/var/run/$prog
 
-fail () {
-  echo $@
-  exit 1
-}
+# color only if printing to terminal
+declare -A COLOR
+if [ -t 1 ]
+then
+  COLOR[RUNNING]=
+  COLOR[STOPPED]=$'\033[46;30m'
+  COLOR[DISABLED]=$'\033[47;38;5;8m'
+  COLOR[OBSOLETE]=$'\033[48;5;8;37m'
+  COLOR[MODIFIED]=$'\033[43;30m'
+  COLOR[DEAD]=$'\033[41;37m'
+  COLOR[NORMAL]=$'\033[0;39m'
+  COLOR[HEADER]=$'\033[0;1;4m'
+fi
+
 
 echo_failure () {
   echo " [failed]"
 }
 
 checkpid () {
-  [ -d /proc/$PID ] 
+  [ -d /proc/$* ]
 }
 
 launch () {
@@ -64,87 +70,129 @@ launch () {
     reload=YES
     shift
   fi
+
+  [ -d /var/run/procServ ] || mkdir -pm 755 /var/run/procServ
+  [ -z "$logdir" -o -d "$logdir" ] || mkdir -pm 755 "$logdir"
+
   temp=$(mktemp -p $(dirname $shells)) || fail "can't create temporary file"
-  while read PORT USER DIR COMMAND ARGS
-  do
-    # check for empty lines and comments
-    [[ $PORT == "" || $PORT == \#* ]] && continue
-
-    # AD84: added
-    DIR=${DIR//_IOCNAME_/$HOSTNAME}
-    ARGS=${ARGS//_IOCNAME_/$HOSTNAME}
-    # AD84: end added
-
-    # check if already started shell is still alive
-    if LINE=$(grep "$PORT $USER $DIR $COMMAND $ARGS" $shells 2> /dev/null)
-    then
-      PID=${LINE%% *}
-      if checkpid $PID
+  # delete entries for dead shell that we are going to restart
+  if [ -f $shells ]
+  then
+    while read -r PID PORT LINE
+    do
+      if ! checkpid $PID
       then
-        if [ -z "$reload" ] && [ -z "$*" ] || echo "$*" | grep -qE "(^|[[:space:]])$PORT([[:space:]]|$)"
-        then
-          echo "Already running: $PORT $USER $DIR $COMMAND $ARGS"
-        fi
-        echo "$LINE" >> $temp
-        continue
+        [ -z "$*" ] && continue
+        for p in "$@"; do [ "$p" = "$PORT" ] && continue 2; done
       fi
+      # keep all other shell entries (dead or running)
+      echo "$PID $PORT $LINE" >> $temp
+      _PID[$PORT]=$PID
+      _LINE[$PORT]="$LINE"
+    done < $shells
+  fi
+
+  # add entries for shells we start
+  while read -r PORT USER DIR COMMAND
+  do
+    # ignore empty lines and comments
+    [ "${PORT%#*}" ] && STATUS=STOPPED || STATUS=DISABLED
+    PORT="${PORT#\#}"
+    test "$PORT" -ge 0 2>/dev/null || continue
+
+    # skip if line does not match given port number
+    if [ "$*" ]
+    then
+      for p in "$@" end; do [ "$p" = "$PORT" ] && break; done
+      [ $p = end ] && continue
     fi
 
-    # check if we have to start all shells or only this PORT
-    [ "$*" ] && echo "$*" | grep -qvE "(^|[[:space:]])$PORT([[:space:]]|$)" && continue
+    if [ $STATUS = DISABLED ]
+    then
+      echo "Shell $PORT has been disabled in the configuration" >&2
+      continue
+    fi
+
+    DIR=${DIR//_IOCNAME_/$HOSTNAME}
+    ARGS=${ARGS//_IOCNAME_/$HOSTNAME}
+
+    # check if this shell had already been started
+    if [ "${_PID[$PORT]}" ]
+    then
+      # warn if trying to start already running shell
+      if [ -z "$reload" ]
+      then
+        if [ "$USER $DIR $COMMAND" != "${_LINE[$PORT]}" ]
+        then
+          echo "Running but modified: ${_LINE[$PORT]}" >&2
+          echo "New configuration   : $USER $DIR $COMMAND" >&2
+          echo "You may want to restart $PORT" >&2
+          mod=1
+        else
+          echo "Already running: $PORT ${_LINE[$PORT]}" >&2
+        fi
+      fi
+      # skip already running shells
+      continue
+    fi
 
     if [ -n "$logdir" ]
     then
-      [ -d $logdir ] || mkdir -m 777 $logdir
       LOG=$logdir/$PORT
       rm -f $LOG
     else
       LOG=/dev/null
     fi
 
-    # start shellbox as other user
-    echo -n Starting: $PORT $USER $DIR $COMMAND $ARGS
-
-    if /usr/bin/sudo -E true 2> /dev/null
+    # start shell
+    echo Starting: $PORT $USER $DIR $COMMAND
+    if [ "$UID" -eq 0 ]
     then
-        SUDO="/usr/bin/sudo -H -u $USER SHELLBOX=$HOSTNAME:$PORT EPICS_HOST_ARCH=$EPICS_HOST_ARCH PATH=$PATH"
-    elif /usr/bin/sudo true 2> /dev/null
-    then
-      	SUDO="/usr/bin/sudo -H -u $USER"
+        # sudo may be installed in different locations
+        # and may delete important environment variables
+        SUDO=$(which sudo) && SUDO+=" -H -u $USER SHELLBOX=$HOSTNAME:$PORT EPICS_HOST_ARCH=$EPICS_HOST_ARCH PATH=$PATH"
     fi
 
-    SUDO="/usr/bin/sudo -H -u $USER SHELLBOX=$HOSTNAME:$PORT EPICS_HOST_ARCH=$EPICS_HOST_ARCH PATH=$PATH"
-
-    #export SHELLBOX=$HOSTNAME:$PORT
-
-    pidfile=/var/run/procServ-$PORT.pid
+    pidfile=/var/run/procServ/$PORT.pid
     rm -f $pidfile
-    L=/tmp/$SHELLBOX.log
-    mknod -m 666 $L p 2>/dev/null 
-    logger -p local0.info -t shellbox["$PORT"] -f $L &
-    $exe -p $pidfile $options $DIR $params -L $L $PORT $SUDO $(which $COMMAND) $ARGS >> $LOG 2>&1 < /dev/null
+    logpipe=/tmp/procServ-$PORT.log
+    mknod -m 666 $logpipe p 2>/dev/null
+    cat $logpipe | logger -p local0.info -t shellbox[$PORT] 2>/dev/null &
+    $exe -p $pidfile $options $DIR -L $logpipe $PORT $SUDO $COMMAND >> $LOG 2>&1 < /dev/null
     # check if starting worked or failed
     usleep 100000
     if [ -e $pidfile ]
     then
       PID=$(<$pidfile)
-      echo "$PID $PORT $USER $DIR $COMMAND $ARGS" >> $temp
-      echo
+      _PID[$PORT]=$PID
+      echo "$PID $PORT $USER $DIR $COMMAND" >> $temp
     else
+      _PID[$PORT]=fail
       echo_failure
       echo
       cat $LOG
     fi
   done < $conf
   mv $temp $shells
-  chmod 0644 $shells
+  chmod 0444 $shells
+  for p in "$@"
+  do
+    if [ -z ${_PID[$p]]} ]
+    then
+      echo "No configuration for $p found" >&2
+    fi
+  done
+
+  [ "$mod" ] && fail "To apply all modifcations use reload"
 }
 
 start () {
   [ -r $conf ] || fail "$conf not readable"
+  exe=$(which procServ) || fail "procServ not found"
   [ -x $exe ] || fail "$exe is not executable"
-  launch $*
+  mkdir -pm 755 /var/lock/subsys
   touch /var/lock/subsys/$prog
+  launch $*
 }
 
 stopshell() {
@@ -162,7 +210,7 @@ stopshell() {
 
 stop () {
   # anything to stop?
-  if [ ! -r $shells ]
+  if [ ! -f $shells ]
   then
     echo "$prog: No shells started."
     exit 0
@@ -170,7 +218,7 @@ stop () {
   if [ -z "$1" ]
   then
     # kill all shellboxes
-    while read PID PORT ARGS
+    while read -r PID PORT ARGS
     do
       stopshell $PID $PORT $ARGS
     done < $shells
@@ -179,31 +227,32 @@ stop () {
   else
     # kill only selected shellboxes
     temp=$(mktemp -p $(dirname $shells)) || fail "can't create temporary file"
-    while read PID PORT ARGS
+    while read -r PID PORT ARGS
     do
-      echo "$*" | grep -qE "(^|[[:space:]])$PORT([[:space:]]|$)" && stopshell $PID $PORT $ARGS || echo "$PID $PORT $ARGS" >> $temp
+      echo "$*" | grep -qE "(^|[[:space:]])$PORT([[:space:]]|$)" && \
+        stopshell $PID $PORT $ARGS || \
+        echo "$PID $PORT $ARGS" >> $temp
     done < $shells
     mv $temp $shells
-    chmod 0644 $shells
+    chmod 0444 $shells
   fi
 }
 
 reload () {
-  echo "Reloading $conf: "
-  [ -r $conf ] || fail "not readable"
+  echo "Reloading $conf... "
+  [ -f $conf ] || fail "not readable"
   # anything to stop?
-  if [ -r $shells ]
+  if [ -f $shells ]
   then
-    #first kill all shells that are not configured any more
+    # first kill all shells that are modified or not configured any more
     temp=$(mktemp -p $(dirname $shells)) || fail "can't create temporary file"
-    while read PID LINE
+    while read -r PID LINE
     do
-      while read PORT USER DIR COMMAND ARGS
+      while read -r PORT USER DIR COMMAND ARGS
       do
-        # AD84: added
         DIR=${DIR//_IOCNAME_/$HOSTNAME}
         ARGS=${ARGS//_IOCNAME_/$HOSTNAME}
-        # AD84: end added
+
         if [ "$PORT $USER $DIR $COMMAND $ARGS" = "$LINE" ]
         then
           echo "Keeping: $LINE"
@@ -214,62 +263,123 @@ reload () {
       stopshell $PID $PORT $LINE
     done < $shells
     mv $temp $shells
-    chmod 0644 $shells
+    chmod 0444 $shells
   fi
-  #now start all new shells
+  # now start all new or modified shells
   sleep 2
   launch -reload
 }
 
 status () {
-  [ -r $conf ] || fail "$conf not readable"
-  if [ "$1" = "-log" ]
-  then
-    log=YES
-    shift
-  fi
-  echo -e "pid\tport\tuser\tdir\t\t\tcommand"
-  while read PORT USER DIR COMMAND ARGS
+  while [ "$1" ]
   do
-    # check for empty lines and comments
-    [[ $PORT == "" || $PORT == \#* ]] && continue
+    case "$1" in
+      -log | --log) log=1; shift ;;
+      --json5) json5=1; shift ;;
+      --) shift; break;;
+      -* ) echo "unknown option $1 ignored" >&2; shift ;;
+      *) break
+    esac
+  done
 
-    # AD84: added
-    DIR=${DIR//_IOCNAME_/$HOSTNAME}
-    ARGS=${ARGS//_IOCNAME_/$HOSTNAME}
-    # AD84: end added
+  # First read all configured shells
+  if [ -f $conf ]
+  then
+    while read -r PORT USER DIR CMD
+    do
+      # Assume stopped until proven otherwise
+      [ "${PORT%#*}" ] && STATUS=STOPPED || STATUS=DISABLED
+      # check for empty lines, comments, rubbish
+      PORT="${PORT#\#}"
+      test "$PORT" -ge 0 2>/dev/null || continue
+      _STATUS[$PORT]=$STATUS
+      _USER[$PORT]=$USER
+      _DIR[$PORT]=${DIR//_IOCNAME_/$HOSTNAME}
+      _CMD[$PORT]=${CMD//_IOCNAME_/$HOSTNAME}
+      _CFG[$PORT]="${_USER[$PORT]} ${_DIR[$PORT]} ${_CMD[$PORT]}"
+    done < $conf
+  fi
 
-    # check if we have to report all shells
-    [ "$*" ] &&  echo "$*" | grep -qvE "(^|[[:space:]])$PORT([[:space:]]|$)" && continue
-    
-    if [ "$logdir" -a "$log" ]
-    then
-      echo "-------------------------------------------------------------------"
-    fi
-    
-    if LINE=$(grep "$PORT $USER $DIR $COMMAND $ARGS" $shells 2> /dev/null)
-    then 
-      PID=${LINE%% *}
+  # Now check all started shells
+  if [ -f $shells ]
+  then
+    while read -r PID PORT USER DIR CMD
+    do
+      CFG="$USER $DIR $CMD"
+      _PID[$PORT]=$PID
+      _USER[$PORT]=$USER
+      _DIR[$PORT]=$DIR
+      _CMD[$PORT]=$CMD
       if checkpid $PID
       then
-        echo -n $PID
+        if [ "${_STATUS[$PORT]}" = DISABLED ]
+        then
+          _STATUS[$PORT]=OBSOLETE
+        elif [ -z "${_CFG[$PORT]}" ]
+        then
+          _STATUS[$PORT]=OBSOLETE
+        elif [ "${_CFG[$PORT]}" != "$CFG" ]
+        then
+          _STATUS[$PORT]=MODIFIED
+        else
+          _STATUS[$PORT]=RUNNING
+        fi
       else
-        $SETCOLOR_FAILURE
-        echo -n DEAD
-        $SETCOLOR_NORMAL
+        _STATUS[$PORT]=DEAD
+        _PID[$PORT]=
       fi
-    else
-      $SETCOLOR_FAILURE
-      echo -n STOPPED 
-      $SETCOLOR_NORMAL
-    fi
-    echo -e "\t$PORT\t$USER\t$DIR\t$COMMAND $ARGS"
-    
+    done < $shells
+  fi
+
+
+  if [ "$json5" ]
+  then
+    echo '{ shells: ['
+    for PORT in ${!_STATUS[*]}
+    do
+      echo '  {'
+      echo '   port: '$PORT','
+      [ "${_PID[$PORT]}" ] && echo '   pid: '${_PID[$PORT]}','
+      echo '   status: "'${_STATUS[$PORT]}'",'
+      echo '   user: "'${_USER[$PORT]}'",'
+      dir=${_DIR[$PORT]//\\/\\\\}
+      echo '   dir: "'${dir//\"/\\\"}'",'
+      cmd=${_CMD[$PORT]//\\/\\\\}
+      echo '   cmd: "'${cmd//\"/\\\"}'"'
+      echo '  },'
+    done
+    echo ']}'
+    exit
+  fi
+
+  USERLEN=0
+  for v in "${_USER[@]}"
+  do
+    [ ${#v} -gt $USERLEN ] && USERLEN=${#v}
+  done
+  DIRLEN=0
+  for v in "${_DIR[@]}"
+  do
+    [ ${#v} -gt $DIRLEN ] && DIRLEN=${#v}
+  done
+  CMDLEN=0
+  for v in "${_CMD[@]}"
+  do
+    [ ${#v} -gt $CMDLEN ] && CMDLEN=${#v}
+  done
+
+  printf "${COLOR[HEADER]}#%-5s  %-8s  %-5s  %-*s  %-*s  %-*s ${COLOR[NORMAL]}\n" pid status port $USERLEN user $DIRLEN dir $CMDLEN command
+
+  for PORT in ${!_STATUS[*]}
+  do
+    # check if we have to report all shells
+    [ "$*" ] &&  echo "$*" | grep -qvE "(^|[[:space:]])$PORT([[:space:]]|$)" && continue
+    printf "${COLOR[${_STATUS[$PORT]}]}%-6s  %-8s  %5d  %-*s  %-*s  %-*s ${COLOR[NORMAL]}\n" "${_PID[$PORT]}" ${_STATUS[$PORT]} $PORT $USERLEN ${_USER[$PORT]} $DIRLEN ${_DIR[$PORT]} $CMDLEN "${_CMD[$PORT]}"
     if [ "$logdir" -a "$log" ]
     then
-        grep '\*\*\*\*' $logdir/$PORT 2>/dev/null
+      grep '\*\*\*\*' $logdir/$PORT 2>/dev/null
     fi
-  done < $conf
+  done
 }
 
 CMD=$1