Accessing a JSON object in Bash - associative array / list / another model
Solution 1:
If you want key and value, and based on How do i convert a json object to key=value format in JQ, you can do:
$ jq -r "to_entries|map(\"\(.key)=\(.value|tostring)\")|.[]" file
SALUTATION=Hello world
SOMETHING=bla bla bla Mr. Freeman
In a more general way, you can store the values into an array myarray[key] = value
like this, just by providing jq
to the while
with the while ... do; ... done < <(command)
syntax:
declare -A myarray
while IFS="=" read -r key value
do
myarray[$key]="$value"
done < <(jq -r 'to_entries|map("(.key)=(.value)")|.[]' file)
And then you can loop through the values like this:
for key in "${!myarray[@]}"
do
echo "$key = ${myarray[$key]}"
done
For this given input, it returns:
SALUTATION = Hello world
SOMETHING = bla bla bla Mr. Freeman
Solution 2:
Although this question is answered, I wasn't able to fully satiate my requirements from the posted answer. Here is a little write up that'll help any bash-newcomers.
Foreknowledge
A basic associative array declaration
#!/bin/bash
declare -A associativeArray=([key1]=val1 [key2]=val2)
You can also use quotes ('
, "
) around the declaration
, its keys
, and
values
.
#!/bin/bash
declare -A 'associativeArray=([key1]=val1 [key2]=val2)'
And you can delimit each [key]=value
pair via space or newline.
#!/bin/bash
declare -A associativeArray([key1]=value1
['key2']=value2 [key3]='value3'
['key4']='value2' ["key5"]="value3"
["key6"]='value4'
['key7']="value5"
)
Depending on your quote variation, you may need to escape your string.
Using Indirection to access both key and value in an associative array
example () {
local -A associativeArray=([key1]=val1 [key2]=val2)
# print associative array
local key value
for key in "${!associativeArray[@]}"; do
value="${associativeArray["$key"]}"
printf '%s = %s' "$key" "$value"
done
}
Running the example function
$ example
key2 = val2
key1 = val1
Knowing the aforementioned tidbits allows you to derive the following snippets:
The following examples will all have the result as the example above
String evaluation
#!/usr/bin/env bash
example () {
local arrayAsString='associativeArray=([key1]=val1 [key2]=val2)'
local -A "$arrayAsString"
# print associative array
}
Piping your JSON into JQ
#!/usr/bin/env bash
# Note: usage of single quotes instead of double quotes for the jq
# filter. The former is preferred to avoid issues with shell
# substitution of quoted strings.
example () {
# Given the following JSON
local json='{ "key1": "val1", "key2": "val2" }'
# filter using `map` && `reduce`
local filter='to_entries | map("[\(.key)]=\(.value)") |
reduce .[] as $item ("associativeArray=("; . + ($item|@sh) + " ") + ")"'
# Declare and assign separately to avoid masking return values.
local arrayAsString;
# Note: no encompassing quotation (")
arrayAsString=$(cat "$json" | jq --raw-output "${filter}")
local -A "$arrayAsString"
# print associative array
}
jq -n / --null-input option + --argfile && redirection
#!/usr/bin/env bash
example () {
# /path/to/file.json contains the same json as the first two examples
local filter filename='/path/to/file.json'
# including bash variable name in reduction
filter='to_entries | map("[\(.key | @sh)]=\(.value | @sh) ")
| "associativeArray=(" + add + ")"'
# using --argfile && --null-input
local -A "$(jq --raw-output --null-input --argfile file "$filename" \
"\$filename | ${filter}")"
# or for a more traceable declaration (using shellcheck or other) this
# variation moves the variable name outside of the string
# map definition && reduce replacement
filter='[to_entries[]|"["+(.key|@sh)+"]="+(.value|@sh)]|"("+join(" ")+")"'
# input redirection && --join-output
local -A associativeArray=$(jq --join-output "${filter}" < "${filename}")
# print associative array
}
Reviewing previous answers
@Ján Lalinský
To load JSON object into a bash associative array efficiently (without using loops in bash), one can use tool 'jq', as follows.
# first, load the json text into a variable: json='{"SALUTATION": "Hello world", "SOMETHING": "bla bla bla Mr. Freeman"}' # then, prepare associative array, I use 'aa': unset aa declare -A aa # use jq to produce text defining name:value pairs in the bash format # using @sh to properly escape the values aacontent=$(jq -r '. | to_entries | .[] | "[\"" + .key + "\"]=" + (.value | @sh)' <<< "$json") # string containing whole definition of aa in bash aadef="aa=($aacontent)" # load the definition (because values may contain LF characters, aadef must be in double quotes) eval "$aadef" # now we can access the values like this: echo "${aa[SOMETHING]}"
Warning: this uses eval, which is dangerous if the json input is from unknown source (may contain malicious shell commands that eval may execute).
This could be reduced to the following
example () {
local json='{ "key1": "val1", "key2": "val2" }'
local -A associativeArray="($(jq -r '. | to_entries | .[] |
"[\"" + .key + "\"]=" + (.value | @sh)' <<< "$json"))"
# print associative array
}
@fedorqui
If you want key and value, and based on How do i convert a json object to key=value format in JQ, you can do:
$ jq -r "to_entries|map(\"\(.key)=\(.value|tostring)\")|.[]" file SALUTATION=Hello world SOMETHING=bla bla bla Mr. Freeman
In a more general way, you can store the values into an array
myarray[key] = value
like this, just by providingjq
to thewhile
with thewhile ... do; ... done < <(command)
syntax:declare -A myarray while IFS="=" read -r key value do myarray[$key]="$value" done < <(jq -r "to_entries|map(\"\(.key)=\(.value)\")|.[]" file)
And then you can loop through the values like this:
for key in "${!myarray[@]}" do echo "$key = ${myarray[$key]}" done
For this given input, it returns:
SALUTATION = Hello world SOMETHING = bla bla bla Mr. Freeman
The main difference between this solution and my own is looping through the array in bash or in jq.
Each solution is valid and depending on your use case, one may be more useful then the other.
Solution 3:
Context: This answer was written to be responsive to a question title which no longer exists..
The OP's question actually describes objects, vs arrays.
To be sure that we help other people coming in who are actually looking for help with JSON arrays, though, it's worth covering them explicitly.
For the safe-ish case where strings can't contain newlines (and when bash 4.0 or newer is in use), this works:
str='["Hello world", "bla bla bla Mr. Freeman"]'
readarray -t array <<<"$(jq -r '.[]' <<<"$str")"
To support older versions of bash, and strings with newlines, we get a bit fancier, using a NUL-delimited stream to read from jq
:
str='["Hello world", "bla bla bla Mr. Freeman", "this is\ntwo lines"]'
array=( )
while IFS= read -r -d '' line; do
array+=( "$line" )
done < <(jq -j '.[] | (. + "\u0000")')
Solution 4:
This is how can it be done recursively:
#!/bin/bash
SOURCE="$PWD"
SETTINGS_FILE="$SOURCE/settings.json"
SETTINGS_JSON=`cat "$SETTINGS_FILE"`
declare -A SETTINGS
function get_settings() {
local PARAMS="$#"
local JSON=`jq -r "to_entries|map(\"\(.key)=\(.value|tostring)\")|.[]" <<< "$1"`
local KEYS=''
if [ $# -gt 1 ]; then
KEYS="$2"
fi
while read -r PAIR; do
local KEY=''
if [ -z "$PAIR" ]; then
break
fi
IFS== read PAIR_KEY PAIR_VALUE <<< "$PAIR"
if [ -z "$KEYS" ]; then
KEY="$PAIR_KEY"
else
KEY="$KEYS:$PAIR_KEY"
fi
if jq -e . >/dev/null 2>&1 <<< "$PAIR_VALUE"; then
get_settings "$PAIR_VALUE" "$KEY"
else
SETTINGS["$KEY"]="$PAIR_VALUE"
fi
done <<< "$JSON"
}
To call it:
get_settings "$SETTINGS_JSON"
The array will be accessed like so:
${SETTINGS[grandparent:parent:child]}
Solution 5:
To load JSON object into a bash associative array efficiently (without using loops in bash), one can use tool 'jq', as follows.
# first, load the json text into a variable:
json='{"SALUTATION": "Hello world", "SOMETHING": "bla bla bla Mr. Freeman"}'
# then, prepare associative array, I use 'aa':
unset aa
declare -A aa
# use jq to produce text defining name:value pairs in the bash format
# using @sh to properly escape the values
aacontent=$(jq -r '. | to_entries | .[] | "[\"" + .key + "\"]=" + (.value | @sh)' <<< "$json")
# string containing whole definition of aa in bash
aadef="aa=($aacontent)"
# load the definition (because values may contain LF characters, aadef must be in double quotes)
eval "$aadef"
# now we can access the values like this: echo "${aa[SOMETHING]}"
Warning: this uses eval, which is dangerous if the json input is from unknown source (may contain malicious shell commands that eval may execute).