Accessing bash array keys (mac) - macos

Question

For some reason, I am unable to access the array keys with the exclamation point syntax:
declare -a sites
sites=(["fr"]="frederick" ["an"]="annapolis")
for i in "${!sites[#]}"
do
echo "key: $i "
done
This Just echo's out "key : 0"
What am I doing wrong here?
Also, I would like to add the value.
So the our put would be:
key : fr , value : frederick

Answer 1

It Can be done in old bash versions.
In older versions of bash you can use the whole environment variable set to implement associative arrays (also called hashes)
export HASH_PREFIX="I_AM_A_HASH"
hash-set() {
HASH_NAME="$1" ; shift
HASH_KEY="$1" ; shift
HASH_VAL="$1" ; shift
eval "export ${HASH_PREFIX}_${HASH_NAME}_KEY_${HASH_KEY}='$HASH_VAL'"
}
hash-get() {
HASH_NAME="$1" ; shift
HASH_KEY="$1" ; shift
eval "echo \"\$${HASH_PREFIX}_${HASH_NAME}_KEY_${HASH_KEY}\""
}
hash-keys() {
HASH_NAME="$1" ; shift
HASH_PREFIX_NAME_LENGTH=$(( ${#HASH_PREFIX} + ${#HASH_NAME} + 6 ))
declare -x | while read -r LINE_READ ; do
LINE_READ="${LINE_READ:11}"
if [ x"${LINE_READ:0:HASH_PREFIX_NAME_LENGTH}" \
= x"${HASH_PREFIX}_${HASH_NAME}_KEY_" \
]
then
LINE_READ="${LINE_READ:HASH_PREFIX_NAME_LENGTH}"
LINE_READ="${LINE_READ/=*/}"
echo "${LINE_READ}"
fi
done
}
hash-set sites "fr" "frederick"
hash-set sites "an" "annapolis"
for i in $(hash-keys sites) ; do
echo "key: $i, value: $(hash-get sites $i)"
done
The keys are restricted to the same characters as Environment Variables (0-9,a-z,A-Z,_).
You could workaround by using "_xx" to mean non-alphanumeric ascii values (example "_5f" for "_" and "_3f" for "?"). rosettacode has how to convert back and forth between ascii characters and hex in pure-bash.
Also on mac laptop you can install homebrew then use it to install a newer bash.
You could also use the full associative arrays in awk or perl or ruby or python.

Answer 2

The problem is declare -a.
As per the man page, it should be declare -A.
declare [-aAfFgilrtux] [-p] [name[=value] ...]
...
-a Each name is an indexed array variable (see Arrays above).
-A Each name is an associative array variable (see Arrays above).
Try this instead:
declare -A sites
sites=(["fr"]="frederick" ["an"]="annapolis")
for i in "${!sites[#]}"
do
echo "key: $i, value: ${sites[$i]}"
done

Answer 3

I think it maybe a lack of capitalization getting in the way...
declare -A _sites=( ["fr"]="frederick" ["an"]="annapolis" )
for i in "${!_sites[#]}"; do
printf '%s -> %s\n' "${i}" "${_sites[$i]}"
done
Resources that where helpful in sorting the above out are not limited to the following;
An answer from #anubhava regarding declare -A usage
An answer from #lhunath that also covers a work around for Bash versions 3 or lower.
After reading the other posted answer's comments I think you'll want that last listed answer's work-around if stuck with older version of Bash that cannot be updated for reasons.
#Fenn a few more notes...
hash-set() {
HASH_NAME="$1" ; shift
HASH_KEY="$1" ; shift
HASH_VAL="$1" ; shift
eval "export ${HASH_PREFIX}_${HASH_NAME}_KEY_${HASH_KEY}='$HASH_VAL'"
}
... without shifting, or eval, and with required arguments might look like...
hash_set(){
local _name="${1:?${FUNCNAME[0]} not provided a Hash Name}"
local _key="${2:?${FUNCNAME[0]} not provided a Hash Key}"
local _value="${3:?${FUNCNAME[0]} not provided a Value}"
declare -g "${HASH_PREFIX}_${_name}_KEY_${_key}='${_value}'"
}
... hopefully this is a bit more helpful in translating that answer into something that can be up-voted.