Linux scripts for datalogging and graphing of the radiation measurements

Here are the scripts that I'm using on my Linux box to capture the measurement data that is sent by my Geiger-Counter processor Computer (RS232) interface.
It sends one line with the radiation value (in mR/h) measured during each sampling period (111.11s).

---

create.sh:

#!/bin/sh
# create.sh - create rrd for storing radiation measurement values (run once)
RRD=rad.rrd

rrdtool create $RRD \
--start 1301511639  --step 111 \
DS:mR-h:GAUGE:333:0:10000.0 \
RRA:AVERAGE:0.5:1:6000  \
RRA:AVERAGE:0.5:6:3000  \
RRA:AVERAGE:0.5:16:3000 

---

sc.sh:

#!/bin/sh
# sc - simple serialport capture script
SERIAL=/dev/ttyS0

# run loop forever:
while true ; do
    read a < $SERIAL
    N="`date  +%s`"
    echo "rrdtool update rad.rrd $N:$a" >> data.log
    rrdtool update rad.rrd $N:$a
    echo $a >> geiger.log
    sh graph.sh
done

---

graph.sh

#!/bin/sh
# graph.sh - generate graphs from rrd

# mR (milliRoentgen) to Roentgen: CDEF:value=mR,1000,/ \
# mR (milliRoentgen) to Sievert: CDEF:value=mR,100000,/ \

rrdtool graph radday.png -s -24h -e now \
 -l 0 -r \
 --alt-y-grid \
 --units-length 5 \
 --units-exponent -6 \
 --width 800 --height 500 \
 -t "Beta+Gamma Radiation last 24h - `date`" \
 --vertical-label "Sievert/h -------->" \
 --right-axis 100:0 \
 --right-axis-label "R/h ------->" \
 --color FONT#000000 -R light --font "DEFAULT:0:DejaVuSansMono" \
 DEF:mR=rad.rrd:mR-h:AVERAGE \
 CDEF:value=mR,100000,/ \
 CDEF:smoothed=value,3333,TRENDNAN \
 VDEF:rad5max=value,MAXIMUM \
 VDEF:rad5min=value,MINIMUM \
 VDEF:rad5avg=value,AVERAGE \
 VDEF:slope=value,LSLSLOPE \
 VDEF:int=value,LSLINT \
 CDEF:trend=value,POP,slope,COUNT,*,int,+ \
 AREA:smoothed#0000ff40: \
 LINE1.5:smoothed#0000ff:" Radiation (avg)   " \
 LINE1:value#ff000080:" Radiation (raw)   " \
 LINE1:trend#000000:"--- trend\c":dashes \
 VDEF:rad5las=value,LAST \
                COMMENT:"      " \
                COMMENT:"Maximum       " \
                COMMENT:"Minimum       " \
                COMMENT:"Average       " \
                COMMENT:"Last          \n" \
                COMMENT:"     " \
                GPRINT:rad5max:"%6.2lf %SSv/h" \
                GPRINT:rad5min:"%6.2lf %SSv/h" \
                GPRINT:rad5avg:"%6.2lf %SSv/h" \
                GPRINT:rad5las:"%6.2lf %SSv/h \l" \

---