Define Hash Tables in Bash #bash

define_hash_tables_in_bash3.bash

#!/usr/bin/env bash

# Assumes you are running with Bash 3
# {see: https://stackoverflow.com/questions/1494178/how-to-define-hash-tables-in-bash}

# First, indirection.
animals_moo=cow; sound=moo; i="animals_$sound"; echo "${!i}"

# Secondly, `declare`:
sound=moo; animal=cow; declare "animals_$sound=$animal"; echo "$animals_moo

# Bring them together

# Set a value:
declare "array_$index=$value"

# Get a value:
arrayGet() {
    local array=$1 index=$2
    local i="${array}_$index"
    printf '%s' "${!i}"
}

define_hash_tables_in_bash4.bash

#!/usr/bin/env bash

# Assumes your are running with Bash 4
# {see: https://stackoverflow.com/questions/1494178/how-to-define-hash-tables-in-bash}

declare -A animals

# You can fill it up with elements using the normal arry assignment operator.
# For example, if you want to have a map of `animal[sound(key)] = animal(value)`:
animals=( animals["moo"]="cow" ["woof"]="dog")

# Or merge them:
# declare -A animals=( animals["moo"]="cow" ["woof"]="dog")

# Then use them just like normal arrays. Use
# * `animals['key']='value'` to set value
# * `"${animals[@]}"` to expand the values
# * `"${!animals[@]}"` (notice the `!`) to expand the keys

# Don't forget to quote them:

echo "${animals[@]}"
for sound in "${!animals[@]}"; do echo "$sound - ${animals[$sound]}"; done