I need to get a specific value from a json file using jq in a bash script (busybox). The json file looks like this:
{
"example.com": {
"backend": "1.3.7"
}
}
In my script there are two variables: project and app - as there are of course multiple projects and applications. I need to use these variable values to get the version value. In this example project is "example.com" and app is "backend"
I tried this
jq --arg p "$project" --arg a "$app" '.[$p].[$a]' file.json
But I do get the error
jq: error: syntax error, unexpected '[', expecting FORMAT or QQSTRING_START (Unix shell quoting issues?) at <top-level>, line 1:
.[$p].[$a]
jq: 1 compile error
You may use it like this:
jq -r --arg p "$project" --arg a "$app" '.[$p][$a]' file.json
or else:
jq -r --arg p "$project" --arg a "$app" '.[$p] | .[$a]' file.json
1.3.7
Related
I've got a jq command that works when running directly from the shell or from within a shell script, but when I try to add variable expansion, I get jq errors for unexpected format or invalid characters. My goal is to have a quick and easy way to update some json configuration.
Here's a simplified example.
The format of the json I'm modifying:
{
"pets": {
"some-new-pet": {
"PetInfo": {
"name": "my-brand-new-pet",
"toys": [
"toy1-postfix",
"toy2-postfix",
"toy3-postfix"
]
}
}
}
}
The jq without variable expansion:
cat myfile.json | jq '.pets."some-new-pet" += {PetInfo: {name: "my-brand-new-pet"}, toys: ["toy1", "toy2", "toy3"]}}'
The above runs fine, and adds the new pets.some-new-pet entry to my json.
Below is what I'm trying to do with variable expansion that fails.
jq_args = "'.pets.\"${PET}\" += {PetInfo: {name: \"${NAME}\"}, toys: [\"${toy1}-postfix\", \"${toy2}-postfix\", \"${toy3}-postfix\"]}}'"
cat myfile.json | jq $jq_args
The error message I get with the above:
jq: error: syntax error, unexpected INVALID_CHARACTER, expecting $end (Unix shell quoting issues?) at <top-level>, line 1: '.pets."some-new-pet"
My file is formatted as utf-8 and uses LF line endings.
I do not recommend constructing a jq filter using variable expansion or printf. It will work for simple cases but will fail if the string contains double quotes, backslashes or control-codes, as they have special meanings inside a JSON string. As an alternative to using printf, jq has a way to pass in variables directly via the command-line, avoiding all these issues.
pet='some-second-pet'
name='my-even-newer'
toy1=toy1
toy2=toy2
toy3=toy3
jq \
--arg pet "$pet" \
--arg name "$name" \
--arg toy1 "$toy1" \
--arg toy2 "$toy2" \
--arg toy3 "$toy3" \
'.pets[$pet] += {
PetInfo: {name: $name},
toys: ["\($toy1)-postfix", "\($toy2)-postfix", "\($toy3)-postfix"]
}' \
myfile.json
Output:
{
"pets": {
"some-new-pet": {
"PetInfo": {
"name": "my-brand-new-pet",
"toys": [
"toy1-postfix",
"toy2-postfix",
"toy3-postfix"
]
}
},
"some-second-pet": {
"PetInfo": {
"name": "my-even-newer-pet"
},
"toys": [
"toy1-postfix",
"toy2-postfix",
"toy3-postfix"
]
}
}
}
It would be cleaner and less error prone to format the string using printf
PET='dog'
NAME='sam'
toy1="t1"
toy2="t2"
toy3="t3"
jq_args=$(printf '.pets."%s" += {PetInfo: {name: "%s"}, toys: ["%s-postfix", "%s-postfix", "%s-postfix"]}}' "${PET}" "${NAME}" "${toy1}" "${toy2}" "${toy3}")
echo "$jq_args"
Result:
.pets."dog" += {PetInfo: {name: "sam"}, toys: ["t1-postfix", "t2-postfix", "t3-postfix"]}
Additionally, redundant quoting could be avoided by quoting the arg on this command
cat myfile.json | jq "$jq_args"
Fix your jq code by removing extra } at end
Fix bash jq call:
Add cotes "..." around your $jq_args
so don't use singles '...' in your jq_args definition
Use printf with -v option to define jq_args:
printf -v jq_args "...format..." value1 value2 ...
So your code became:
PET="some-new-pet"
NAME="my-brand-new-pet"
toy1="toy1"
toy2="toy2"
toy3="toy3"
format='.pets."%s" += {PetInfo: {name: "%s"}, toys: ["%s", "%s", "%s"]}'
printf -v jq_args "${format}" "${PET}" "${NAME}" "${toy1}" "${toy2}" "${toy3}"
cat myfile.json | jq "$jq_args"
Output:
{
"pets": {
"some-new-pet": {
"PetInfo": {
"name": "my-brand-new-pet"
},
"toys": [
"toy1",
"toy2",
"toy3"
]
}
}
}
Notes:
When you define your format, you put it into simple cotes '...'. It's really better to format JSON (or XML) without back-slashes (\\) before each double cotes (")
Use printf -v variable_name. It's more readable than var_name=$(printf ...)
By constructing the jq filter ("code") using outer bash variables ("data") you may run into escaping issues, which could eventually break or even divert your filter. (see https://en.wikipedia.org/wiki/Code_injection)
Instead, use mechanisms by jq to introduce external data through variables (parameter --arg):
jq --arg pet "${PET}" \
--arg name "${NAME}" \
--arg toy1 "${toy1}-postfix" \
--arg toy2 "${toy2}-postfix" \
--arg toy3 "${toy3}-postfix" \
'
.pets[$pet] += {PetInfo: {$name, toys: [$toy1,$toy2,$toy3]}}
' myfile.json
If you have an unknown number of variables to include, check out jq's --args parameter (note the additional s)
I want to populate json template with value "Hello Jack", but the "Hello" part shall remain inside of template, is there are any way of doing that, I've tried code below but it gives me error:
jq -n --arg person "Jack" '{my_key: "Hello "$person}'
jq: error: syntax error, unexpected '$', expecting '}' (Unix shell quoting issues?) at <top-level>, line 1:
Use string interpolation syntax like so:
jq -n --arg person Jack '{my_key: "Hello \($person)"}'
And to load the template from a file, use the -f switch:
$ cat template.json
{
"my_key": "Hello \($person)"
}
$ jq -n --arg person Jack -f template.json
{
"my_key": "Hello Jack"
}
I have a JSON file and I'm trying to add another field to it.
Example JSON File:
{"data":{}}
Looking at other answers the += seems to work:
objectName="objName"
cat $jsonFile | jq --arg objName $objectName '.data[$objName] += {"test": "json"}'
Outputs
{
"data": {
"objName": {
"test": "json"
}
}
}
just as expected.
The problem is that I can't hardcode the JSON so I'm inputting the string as a variable. But I can't get the syntax to work:
objectName="objName"
objJSON='{"test": "json"}'
cat $jsonFile | jq -r --arg objName $objectName --arg jsonString $objJSON '.data[$objName] += $jsonString'
I'm getting the error jq: error: syntax error, unexpected INVALID_CHARACTER, expecting $end (Unix shell quoting issues?) at <top-level>, line 1: "json"}
Use --argjson rather than --arg when passing JSON rather than strings.
When in doubt, quote your strings; that way if the shell executing your code isn't the one you think it is, you won't have your values being munged. (It's also helpful to stay in the habits necessary to write portable code; the whole reason I dropped zsh after spending 6 months learning it back in the mid-2000s is that my code quality when writing for other shells suffered).
objName="objName"
objJSON='{"test": "json"}'
echo '{"data":{}}' |
jq --arg objectName "$objName" \
--argjson jsonString "$objJSON" \
'.data[$objectName] += $jsonString'
...properly emits:
{
"data": {
"objName": {
"test": "json"
}
}
}
Given the following input:
J='{"a":1,"b":10,"c":100}
{"a":2,"b":20,"c":200}
{"a":3,"b":30,"c":300}'
The command
SELECT='a,b'; echo $J | jq -c -s --arg P1 $SELECT '.[]|{a,b}'
produces
{"a":1,"b":10}
{"a":2,"b":20}
{"a":3,"b":30}
but this command produces unexpected results:
SELECT='a,b'; echo $J | jq -c -s --arg P1 $SELECT '.[]|{$P1}'
{"P1":"a,b"}
{"P1":"a,b"}
{"P1":"a,b"}
How does one get jq to treat an arg string literally?
Using tostring gives an error
SELECT='a,b'; echo $J | jq -c -s --arg P1 $SELECT '.[]|{$P1|tostring}'
jq: error: syntax error, unexpected '|', expecting '}' (Unix shell quoting
issues?) at <top-level>, line 1:
.[]|{$SELECT|tostring}
jq: 1 compile error
SELECT needs to be a variable and not hardcoded in the script.
SELECT needs to be a variable and not hardcoded in the script.
Assuming you want to avoid the risks of "code injection" and that you want the shell variable SELECT to be a simple string such as "a,b", then consider this reduce-free solution along the lines you were attempting:
J='{"a":1,"b":10,"c":100}'
SELECT='a,b'
echo "$J" |
jq -c --arg P1 "$SELECT" '
. as $in | $P1 | split(",") | map( {(.): $in[.]} ) | add'
Output:
{"a":1,"b":10}
If you really want your data to be parsed as syntax...
This is not an appropriate use case for --arg. Instead, substitute into the code:
select='a,b'; jq -c -s '.[]|{'"$select"'}' <<<"$j"
Note that this has all the usual caveats of code injection: If the input is uncontrolled, the output (or other behavior of the script, particularly if jq gains more capable I/O features in the future) should be considered likewise.
If you want to split the literal string into a list of keys...
Here, we take your select_str (of the form a,b), and generate a map: {'a': 'a', 'b': 'b'}; then, we can break each data item into entries, select only the items in the map, and there's our output.
jq --arg select_str "$select" '
($select_str
| split(",")
| reduce .[] as $item ({}; .[$item]=$item)) as $select_map
| with_entries(select($select_map[.key]))' <<<"$j"
How to make jq treat an input argument as numeric instead of string? In the following example, CURR_INDEX is a Bash variable which has array index value that I want to extract.
jq --arg ARG1 $CURR_INDEX '.[$ARG1].patchSets' inputfile.json
I get the following error:
jq: error: Cannot index array with string
I tried the workaround of using bash eval but some jq filters do not work properly in eval statements.
You can convert it to a number, like this:
jq --arg ARG1 1 '.[$ARG1|tonumber]' <<< '["foo". "bar"]'
"bar"
--arg always binds the value as a string. You can use --argjson (introduced in version 1.5) to treat the argument as a json-encoded value instead.
jq --argjson ARG1 $CURR_INDEX '.[$ARG1].patchSets' inputfile.json
To see it in action, you can reproduce your original error:
$ jq --argjson ARG1 '"1"' '.[$ARG1]' <<< '["foo", "bar"]'
jq: error (at <stdin>:1): Cannot index array with string "1"
then correct it:
$ jq --argjson ARG1 1 '.[$ARG1]' <<< '["foo", "bar"]'
"bar"