[GRASS5] viewing map attribute table

[Hamish]

> Thinking about this a little more: it should be possible to select the
> contents of two columns into two arrays, do the calculation in the
> shell script and then update a third column with the resulting values.
> However, I am not sure if all shells support arrays ?


I think you will need to save to temp files. (use g.tempfile)


hints--


integer math in a shell:

expr 1 + 2



integer math in a bash shell:

echo $(( 1 + 2 ))



floating point math using "bc":

echo "scale=6;  1 / 2" | bc

But "bc" in not guaranteed to be installed on all systems.


floating point math using "awk":

echo "1 2" | awk '{print $1 / $2}'




then add column and populate with
echo "INSERT INTO $NAME VALUES ()" | db.execute



Hamish