Slice an array with spaces in bash

Question

I want to use a key-value storage in bash, and then access the elements and work with them. I have the following code so far, which finds the key in the storage, but can't extract the values from the array without interpreting the spaces.

A straight forward solution to this (since I know there will be three values for each key) is to access those directly, but surely there must be a way to slice the array properly.

# the array is a key: value storage, the keys do not contain spaces, but the values might
# there are always three values for each key, but the number of words in them is unknown
services=("key1" "some values" "another_value" "a lot of values"
          "key2" "other values" "simple_value2" "a lot of values here"
          "key3" "something else here" "another_value3" "whatever")

# this should look for the given value in the array and return the key and respective values if its found
function find_key () {
    arr=("${@:2}")
    len=$(( ${#arr[@]} -1 ))
    for i in $(seq 0 4 "$len")
    do
    if [[ ${arr[$i]} == "$1" ]] ; then
        # this should get the i'th element and 4 following elements (the values), which works correctly
        result="${arr[*]:$i:4}"
        # at this point result is just a regular array and there is no way to separate the values again

        # this prints just one line with all words
        for x in "${result[@]}"; do
            echo "element: '$x'"
        done

        # I want to return the array ("key" "value 1" "value 2" "the third value") from here to work with it later
        echo "${result[@]}"
        return 0
    fi
    done
    return 1
}

key_and_values="$(find_key "key2" "${services[@]}")"
echo "${key_and_values[@]}"

The output is:

element: 'key2 other values simple_value2 a lot of values here'
key2 other values simple_value2 a lot of values here

And I am looking for:

element: 'key2'
element: 'other values'
element: 'simple_value2'
element: 'a lot of values here'
key2 other values simple_value2 a lot of values here

No, it is not. The problem is at the line result="${arr[*]:$i:4}", where it changes from array to string — drali
– drali, Commented Feb 19, 2020 at 10:43

KamilCuk · Accepted Answer · 2020-02-19 10:56:03Z

1

Change:

result="${arr[*]:$i:4}"

into an array:

result=("${arr[@]:$i:4}")

There are some problems with your script:

"${key_and_values[@]}" - key_and_values is not an array, it's a normal variable.
echo "${result[@]}" will work abnormally when for example result[0]='-n'. Use printf "%s\n" "${result[@]}" | paste -sd ' ' or similar.

I think I would go with something along:

find_key() {
    arr=("${@:2}")
    for ((i=0; i < ${#arr[@]}; i+=4)); do
        if [[ ${arr[$i]} == "$1" ]] ; then
            printf "%s\0" "${arr[@]:$i:4}"
            return 0
        fi
    done
    return 1
}

readarray -d '' -t key_and_values < <(find_key "key2" "${services[@]}")
printf "element: %s\n" "${key_and_values[@]}"
printf "%s\n" "${key_and_values[@]}" | paste -sd' '

edited Feb 19, 2020 at 10:56

answered Feb 19, 2020 at 10:48

KamilCuk

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Comments

Ivan · Accepted Answer · 2020-02-19 11:34:30Z

0

I use this tehniq in piu-piu

array=("abs 123 ---" "DEF 456 +++")
for items in "${array[@]}"; {
    sub=( $items )
    echo  ======
    for item in ${sub[@]}; {
        echo $item
    }
}

output

======
abs
123
---
======
DEF
456
+++

Also you can use an associative array and loop over indexes

declare -A items=( [item1]="123 abc" [item2]="dfe 234" )

for key in ${!items[@]}; {
    echo "key=$key"
    echo "val=${items[$key]}"
}

output

key=item2
val=dfe 234
key=item1
val=123 abc

But the question was about slicing right?), of course you can slice an array like this

array=("abs 123" "DEF 456" "ASA 789")

$ echo "${array[@]:1}"
DEF 456 ASA 789

$ echo "${array[@]::1}"
abs 123

$ echo "${array[@]:1:3}"
DEF 456 ASA 789

$ echo "${array[@]:1:1}"
DEF 456

edited Feb 19, 2020 at 11:34

answered Feb 19, 2020 at 11:25

Ivan

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