#! /bin/bash
# array-append.bash
# Copyright (c) Michael S. Zick, 2003, All rights reserved.
# License: Unrestricted reuse in any form, for any purpose.
# Version: $ID$
#
# Slightly modified in formatting by M.C.
# Array operations are Bash-specific.
# Legacy UNIX /bin/sh lacks equivalents.
# Pipe the output of this script to 'more'
#+ so it doesn't scroll off the terminal.
# Subscript packed.
declare -a array1=( zero1 one1 two1 )
# Subscript sparse ([1] is not defined).
declare -a array2=( [0]=zero2 [2]=two2 [3]=three2 )
echo
echo '- Confirm that the array is really subscript sparse. -'
echo "Number of elements: 4" # Hard-coded for illustration.
for (( i = 0 ; i < 4 ; i++ ))
do
echo "Element [$i]: ${array2[$i]}"
done
# See also the more general code example in basics-reviewed.bash.
declare -a dest
# Combine (append) two arrays into a third array.
echo
echo 'Conditions: Unquoted, default IFS, All-Elements-Of operator'
echo '- Undefined elements not present, subscripts not maintained. -'
# # The undefined elements do not exist; they are not being dropped.
dest=( ${array1[@]} ${array2[@]} )
# dest=${array1[@]}${array2[@]} # Strange results, possibly a bug.
# Now, list the result.
echo
echo '- - Testing Array Append - -'
cnt=${#dest[@]}
echo "Number of elements: $cnt"
for (( i = 0 ; i < cnt ; i++ ))
do
echo "Element [$i]: ${dest[$i]}"
done
# Assign an array to a single array element (twice).
dest[0]=${array1[@]}
dest[1]=${array2[@]}
# List the result.
echo
echo '- - Testing modified array - -'
cnt=${#dest[@]}
echo "Number of elements: $cnt"
for (( i = 0 ; i < cnt ; i++ ))
do
echo "Element [$i]: ${dest[$i]}"
done
# Examine the modified second element.
echo
echo '- - Reassign and list second element - -'
declare -a subArray=${dest[1]}
cnt=${#subArray[@]}
echo "Number of elements: $cnt"
for (( i = 0 ; i < cnt ; i++ ))
do
echo "Element [$i]: ${subArray[$i]}"
done
# The assignment of an entire array to a single element
#+ of another array using the '=${ ... }' array assignment
#+ has converted the array being assigned into a string,
#+ with the elements separated by a space (the first character of IFS).
# If the original elements didn't contain whitespace . . .
# If the original array isn't subscript sparse . . .
# Then we could get the original array structure back again.
# Restore from the modified second element.
echo
echo '- - Listing restored element - -'
declare -a subArray=( ${dest[1]} )
cnt=${#subArray[@]}
echo "Number of elements: $cnt"
for (( i = 0 ; i < cnt ; i++ ))
do
echo "Element [$i]: ${subArray[$i]}"
done
echo '- - Do not depend on this behavior. - -'
echo '- - This behavior is subject to change - -'
echo '- - in versions of Bash newer than version 2.05b - -'
# MSZ: Sorry about any earlier confusion folks.
exit 0