#! /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