Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
Example 26−10. Simulating a two−dimensional array, then tilting it
#!/bin/bash
# Simulating a two−dimensional array.
# A two−dimensional array stores rows sequentially.
Rows=5
Columns=5
declare −a alpha
# char alpha [Rows] [Columns];
# Unnecessary declaration.
load_alpha ()
{
local rc=0
local index
for i in A B C D E F G H I J K L M N O P Q R S T U V W X Y
do
local row=`expr $rc / $Columns`
local column=`expr $rc % $Rows`
let "index = $row * $Rows + $column"
alpha[$index]=$i # alpha[$row][$column]
let "rc += 1"
done
# Simpler would be
# declare −a alpha=( A B C D E F G H I J K L M N O P Q R S T U V W X Y )
# but this somehow lacks the "flavor" of a two−dimensional array.
}
print_alpha ()
{
local row=0
local index
echo
while [ "$row" −lt "$Rows" ]
do
local column=0
# Print out in "row major" order −
# columns vary
# while row (outer loop) remains the same.
while [ "$column" −lt "$Columns" ]
do
let "index = $row * $Rows + $column"
echo −n "${alpha[index]} " # alpha[$row][$column]
let "column += 1"
done
let "row += 1"
echo
done
# The simpler equivalent is
# echo ${alpha[*]} | xargs −n $Columns
echo
}
Chapter 26. Arrays 307