Extract value from bash array with a delimiter-CodePudding

I have an array my_array=(foo:123 bar:456 baz:789 lorem:012 ipsum:345)

I want to extract the value after delimiter for a given key

eg. passing foo should return 123. Similarly, passing lorem should return 012

CodePudding user response：

If it is acceptable to prepare another (associative) array variable, how about:

#!/bin/bash

my_array=(foo:123 bar:456 baz:789 lorem:012 ipsum:345)
declare -A $(printf "%s\n" "${my_array[@]}" | sed 's/\(.*\):\(.*\)/my_array2[\1]=\2/')

declare -p my_array2

Output:

declare -A my_array2=([bar]="456" [baz]="789" [foo]="123" [lorem]="012" [ipsum]="345" )

Then echo "${my_array2[foo]}" will output 123 as an example.

Please note passing variables or command outputs to declare has a possible vulnerability risk. Make sure the strings in my_array are fully under control.

CodePudding user response：

If you just need to access a few keys then you might consider something like:

#!/bin/bash
shopt -s extglob

my_array=(foo:123 bar:456 baz:789 lorem:012 ipsum:345)

my_key=lorem
my_val=${my_array[@]/@("$my_key":|!("$my_key":*))/}

echo "$my_val"

If you'll be accessing a lot of keys then the previous method is too inefficient so you'll need to build an associative array (bash 4 ):

#!/bin/bash

my_array=(foo:123 bar:456 baz:789 lorem:012 ipsum:345)

declare -A my_hash
for elem in "${my_array[@]}"
do
    IFS=':' read -r key val <<< "$elem"
    my_hash["$key"]=$val
done

echo "${my_hash[lorem]}"

CodePudding user response：

If you are using older bash versions where associative arrays are not available you could use bash regex matching and parameter substitution:

#!/bin/bash

pattern=${1:-lorem}

arr=(foo:123 bar:456 baz:789 lorem:012 ipsum:345)

for i in "${arr[@]}" ; do
    if [[ "${i}" =~ ^${pattern}:* ]] ; then
        echo "${i##*:}"
    fi
done

Output:

$ ./foo.sh   # default pattern is lorem
012
$ ./script foo
123
$ ./script bar
456
$ ./script baz
789
$ ./script lorem
012
$ ./script ipsum
345