92 lines
2.0 KiB
Bash
Executable File
92 lines
2.0 KiB
Bash
Executable File
#!/bin/bash
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#-------------------------------------------------------------------------------
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# Example 1 for Bash Tips show 20: deleting individual array elements
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#-------------------------------------------------------------------------------
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#
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# Seed the random number generator with a nanosecond number
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#
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RANDOM=$(date +%N)
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echo "Indexed array"
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echo "-------------"
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#
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# Create indexed array and populate with ad ae ... cf
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#
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declare -a iarr
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mapfile -t iarr < <(printf '%s\n' {a..c}{d..f})
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#
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# Report element count and show the structure
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#
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echo "Length: ${#iarr[*]}"
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declare -p iarr
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#
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# Unset a random element
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#
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ind=$((RANDOM % ${#iarr[*]}))
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echo "Element $ind to be removed, contents: ${iarr[$ind]}"
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unset "iarr[$ind]"
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#
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# Report on the result of the element removal
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#
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echo "Length: ${#iarr[*]}"
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declare -p iarr
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echo
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echo "Associative array"
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echo "-----------------"
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#
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# Create associative array. Populate with the indices from the indexed array
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# using the array contents as the subscripts.
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#
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declare -A aarr
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for (( i = 0; i <= ${#iarr[*]}; i++ )); do
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# If there's a "hole" in iarr don't create an element
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[[ -v iarr[$i] ]] && aarr[${iarr[$i]}]=$i
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done
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#
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# Report element count and keys
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#
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echo "Length: ${#aarr[*]}"
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echo "Keys: ${!aarr[*]}"
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#
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# Use a loop to report array contents in sorted order
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#
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for key in $(echo "${iarr[@]}" | sort); do
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echo "aarr[$key]=${aarr[$key]}"
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done
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#
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# Make another contiguous indexed array of the associative array's keys. We
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# don't care about their order
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#
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declare -a keys
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mapfile -t keys < <(printf '%s\n' ${!aarr[*]})
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#
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# Unset a random element. The indexed array 'keys' contains the keys
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# of the associative array so we use the selected one as a subscript. We use
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# this array because it doesn't have any "holes". If we'd used 'iarr' we might
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# have hit the "hole" we created earlier!
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#
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k=$((RANDOM % ${#keys[*]}))
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echo "Element '${keys[$k]}' to be removed, contents: ${aarr[${keys[$k]}]}"
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unset "aarr[${keys[$k]}]"
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#
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# Report final element count and keys
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#
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echo "Length: ${#aarr[*]}"
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echo "Keys: ${!aarr[*]}"
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declare -p aarr
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exit
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