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@jayliew
Created January 16, 2021 21:40
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Cheat sheet for using a bash "dictionary". Also known as a hash or an associative array
#!/bin/bash
################################################################################
#
# Cheat sheet for using a bash "dictionary". Also known as a hash or
# associative array. Because the stone ages need modern data structures too.
#
# jayliew (a) jayliew (.) com
#
################################################################################
# declare hash / dictionary / associative array
declare -A dictionary
dictionary["key1"]="value1"
dictionary["key2"]="value2"
################################################################################
# access an element
echo ${dictionary["key1"]}
################################################################################
# get all values (1 long string, space delimited)
echo ${dictionary[@]}
################################################################################
# get all keys (1 long string, space delimited)
echo ${!dictionary[@]}
################################################################################
# how to iterate through keys
for key in "${!dictionary[@]}"; do
echo $key
done
################################################################################
# check if key exists
test_key="key3"
if [ ${dictionary[${test_key}]+true} ] ; then
echo "key exists"
else
echo "key does NOT exist"
fi
################################################################################
# function to test if key exists
does_key_exist() {
local -n arr=$1 # argument passed by reference
for key in "${!arr[@]}"; do
if [[ $key == $2 ]]; then
echo "exists" # this is the actual returned value
return 0 # must return to break out of loop (0 status code == success)
fi
done
echo "does_not_exist"
return 1 # status code: unsuccessful
}
# usage: does_key_exist dictionary_name key_name
ret_val=$(does_key_exist dictionary "key2")
echo "Returned value is: ${ret_val}"
################################################################################
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