sh script to convert inches to mm and cm

[J65nko]

I found a few interesting DIY wood working projects on the interwebs and because the measurements were in inches I wrote a simple sh script to convert these to millimeters and centimeters.

#!/bin/sh

# use 'bc(1)', the multiprecision calculator to convert inches to mm and cm

INCH='25.4'     # millimeter (mm)
PRECISION=4     # nr of fractional digits

VALUE=1

cat <<END
You can enter values like '1 1/4' or '2 3/8' inch as '1+1/4' and '2+3/8'
-----------------------
Nr of inches: 1/8
1/8 inch = 3.1750 mm or .3175 cm

Nr of inches: 1+1/4
1+1/4 inch = 31.7500 mm or 3.1750 cm
-----------------------

Press CNTRL-C to exit.

END

while true ; do    
        printf "\nNr of inches: " 
        read VALUE
        MM=$( echo "scale = ${PRECISION} ; ( ${VALUE} ) * ${INCH}" | bc )
        CM=$( echo "scale = ${PRECISION} ; ${MM} / 10" | bc )
        echo "${VALUE} inch = ${MM} mm or ${CM} cm"
done

Example where I convert the size of a 2 by 4" and the 1/16" holes to drill in a 3/4" PVC irrigation pipe:

$ ./inch2milli.sh
You can enter values like '1 1/4' or '2 3/8' inch as '1+1/4' and '2+3/8'
-----------------------
Nr of inches: 1/8
1/8 inch = 3.1750 mm or .3175 cm

Nr of inches: 1+1/4
1+1/4 inch = 31.7500 mm or 3.1750 cm
-----------------------

Press CNTRL-C to exit.


Nr of inches: 2
2 inch = 50.8 mm or 5.0800 cm

Nr of inches: 4
4 inch = 101.6 mm or 10.1600 cm

Nr of inches: 1/16
1/16 inch = 1.5875 mm or .1587 cm

Nr of inches: 3/4
3/4 inch = 19.0500 mm or 1.9050 cm

Nr of inches: ^C$