I want to write/make/use a 3D array of [m][n][k] in BASH. From what I understand, BASH does not support array that are not 1D.
Any ideas how to do it?
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3 Answers
Fake multi-dimensionality with a crafted associative array key:
declare -A ary
for i in 1 2 3; do
for j in 4 5 6; do
for k in 7 8 9; do
ary["$i,$j,$k"]=$((i*j*k))
done
done
done
for key in "${!ary[@]}"; do printf "%s\t%d\n" "$key" "${ary[$key]}"; done | sort
1,4,7 28
1,4,8 32
1,4,9 36
1,5,7 35
1,5,8 40
1,5,9 45
1,6,7 42
1,6,8 48
1,6,9 54
2,4,7 56
2,4,8 64
2,4,9 72
2,5,7 70
2,5,8 80
2,5,9 90
2,6,7 84
2,6,8 96
2,6,9 108
3,4,7 84
3,4,8 96
3,4,9 108
3,5,7 105
3,5,8 120
3,5,9 135
3,6,7 126
3,6,8 144
3,6,9 162
I used sort because keys of an assoc.array have no inherent order.
Comments
You can use associative arrays if your bash is recent enough:
unset assoc
declare -A assoc
assoc["1.2.3"]=x
But, I'd rather switch to a language that supports multidimensional arrays (e.g. Perl).
1 Comment
amphetamachine
Good practice is to
unset assoc before using declare because it'll cause an error if assoc is already a non-associative array. (i.e. foo=(1,2,3); declare -A foo causes an error)As in C, you can simulate multidimensional array using an offset.
#! /bin/bash
xmax=100
ymax=150
zmax=80
xymax=$((xmax*ymax))
vol=()
for ((z=0; z<zmax; z++)); do
for ((y=0; y<ymax; y++)); do
for ((x=0; x<xmax; x++)); do
((t = z*xymax+y*xmax+x))
if ((vol[t] == 0)); then
((vol[t] = vol[t-xymax] + vol[t-ymax] + vol[t-1]))
fi
done
done
done
