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