I am trying to format a json string using jq with expected output like this:
[
{
"command": [
"printf 'this is a text'"
]
}
]
However, I cannot get it to work for the single quotes ('), e.g. $ jq -n '[{"command": ["printf 'this is a text'"]}]' gives me a compile error.
I also thought about escaping all double quotes e.g. jq -n "[{\"command\": [\"printf 'this is a text'\"]}]", this is fine however the json string is passed in from a function, I can replace all double quotes with \" first and then run the jq command but it's not very elegant.
Is there a better way to handle the single quotes inside a json string?
Here are four alternatives that should work with a bash or bash-like shell. They can be adapted for other shells as well.
jq -n $'[{"command": ["printf \'this is a text\'"]}]'
cat << EOF | jq .
[{"command": ["printf 'this is a text'"]}]
EOF
jq --arg cmd "printf 'this is a text'" -n '[{command: [ $cmd ]}]'
VAR="[{\"command\": [\"printf 'this is a text'\"]}]"
jq -n --argjson var "$VAR" '$var'
See also How to escape single quotes within single quoted strings
Trying to write a bash script that replaces values in a JSON file we are running into issues with Environment Variables that contain whitespaces.
Given an original JSON file.
{
"version": "base",
"myValue": "to be changed",
"channelId": 0
}
We want to run a command to update some variables in it, so that after we run:
CHANNEL_ID=1701 MY_VALUE="new value" ./test.sh
The JSON should look like this:
{
"version": "base",
"myValue": "new value",
"channelId": 1701
}
Our script is currently at something like this:
#!/bin/sh
echo $MY_VALUE
echo $CHANNEL_ID
function replaceValue {
if [ -z $2 ]; then echo "Skipping $1"; else jq --argjson newValue \"${2}\" '. | ."'${1}'" = $newValue' build/config.json > tmp.json && mv tmp.json build/config.json; fi
}
replaceValue channelId ${CHANNEL_ID}
replaceValue myValue ${MY_VALUE}
In the above all values are replaced by string and strings are getting truncated at whitespace. We keep alternating between this issue and a version of the code where substitutions just stop working entirely.
This is surely an issue with expansions but we would love to figure out, how we can:
- Replace values in the JSON with both strings and values.
- Use whitespaces in the strings we pass to our script.
You don't have to mess with --arg or --argjson to import the environment variables into jq's context. It can very well read the environment on its own. You don't need a script separately, just set the values along with the invocation of jq
CHANNEL_ID=1701 MY_VALUE="new value" \
jq '{"version": "base", myValue: env.MY_VALUE, channelId: env.CHANNEL_ID}' build/config.json
Note that in the case above, the variables need not be exported globally but just locally to the jq command. This allows you to not export multiple variables into the shell and pollute the environment, but just the ones needed for jq to construct the desired JSON.
To make the changes back to the original file, do > tmp.json && mv tmp.json build/config.json or more clearly download the sponge(1) utility from moreutils package. If present, you can pipe the output of jq as
| sponge build/config.json
Pass variables with --arg. Do:
jq --arg key "$1" --arg value "$2" '.[$key] = $value'
Notes:
#!/bin/sh indicates that this is posix shell script, not bash. Use #!/bin/bash in bash scripts.
function replaceValue { is something from ksh shell. Prefer replaceValue() { to declare functions. Bash obsolete and deprecated syntax.
Use newlines in your script to make it readable.
--argjson passes a json formatted argument, not a string. Use --arg for that.
\"${2}\" doesn't quote $2 expansion - it only appends and suffixes the string with ". Because the expansion is not qouted, word splitting is performed, which causes your input to be split on whitespaces when creating arguments for jq.
Remember to quote variable expansions.
Use http://shellcheck.net to check your scripts.
. | means nothing in jq, it's like echo $(echo $(echo))). You could jq '. | . | . | . | . | .' do it infinite number of times - it passes the same thing. Just write the thing you want to do.
Do:
#!/bin/bash
echo "$MY_VALUE"
echo "$CHANNEL_ID"
replaceValue() {
if [ -z "$2" ]; then
echo "Skipping $1"
else
jq --arg key "$1" --arg value "$2" '.[$key] = $value' build/config.json > tmp.json &&
mv tmp.json build/config.json
fi
}
replaceValue channelId "${CHANNEL_ID}"
replaceValue myValue "${MY_VALUE}"
#edit Replaced ."\($key)" with easier .[$key]
jq allows you to build new objects:
MY_VALUE=foo;
CHANNEL_ID=4
echo '{
"version": "base",
"myValue": "to be changed",
"channelId": 0
}' | jq ". | {\"version\": .version, \"myValue\": \"$MY_VALUE\", \"channelId\": $CHANNEL_ID}"
The . selects the whole input, and inputs that (|) to the construction of a new object (marked by {}). For version is selects .version from the input, but you can set your own values for the other two. We use double quotes to allow the Bash variable expansion, which means escaping the double quotes in the JSON.
You'll need to adapt my snippet above to scriptify it.
My Bash script has lots of variable assignments which are put in a JSON file:
var='Hello
"world".
This is \anything \or \nothing
'
echo "{ \"var\"= \"$var\" }" > output.json
When validating the file output.json jq says:
$ cat output.json | jq .
parse error: Invalid numeric literal at line 1, column 9
How can I make a valid JSON file out of it? Any \ and " should be preserved.
The correct JSON string would be
{ "var": "Hello
\"world\".
This is \\anything \\or \\nothing
" }
I cannot modify the variable assignments but the JSON creation.
Pass $var as a raw string argument and JQ will automatically convert it to a valid JSON string.
$ jq -n --arg var "$var" '{$var}'
{
"var": "Hello\n \"world\". \n This is \\anything \\or \\nothing\n"
}
"JSON strings can not contain line feeds", as oguz ismail already mentioned, so it's better to let dedicated tools like xidel (or jq) convert the line feeds to a proper escape sequence and to valid JSON.
Stdin:
$ var='Hello
"world".
This is \anything \or \nothing
'
$ xidel - -se '{"var":$raw}' <<< "$var"
{
"var": "Hello\n \"world\". \n This is \\anything \\or \\nothing\n"
}
Environment variable:
$ export var='Hello
"world".
This is \anything \or \nothing
'
$ xidel -se '{"var":environment-variable("var")}'
{
"var": "Hello\n \"world\". \n This is \\anything \\or \\nothing\n"
}
I need to read these bash variables into my JSON string and I am not familiar with bash. any help is appreciated.
#!/bin/sh
BUCKET_NAME=testbucket
OBJECT_NAME=testworkflow-2.0.1.jar
TARGET_LOCATION=/opt/test/testworkflow-2.0.1.jar
JSON_STRING='{"bucketname":"$BUCKET_NAME"","objectname":"$OBJECT_NAME","targetlocation":"$TARGET_LOCATION"}'
echo $JSON_STRING
You are better off using a program like jq to generate the JSON, if you don't know ahead of time if the contents of the variables are properly escaped for inclusion in JSON. Otherwise, you will just end up with invalid JSON for your trouble.
BUCKET_NAME=testbucket
OBJECT_NAME=testworkflow-2.0.1.jar
TARGET_LOCATION=/opt/test/testworkflow-2.0.1.jar
JSON_STRING=$( jq -n \
--arg bn "$BUCKET_NAME" \
--arg on "$OBJECT_NAME" \
--arg tl "$TARGET_LOCATION" \
'{bucketname: $bn, objectname: $on, targetlocation: $tl}' )
You can use printf:
JSON_FMT='{"bucketname":"%s","objectname":"%s","targetlocation":"%s"}\n'
printf "$JSON_FMT" "$BUCKET_NAME" "$OBJECT_NAME" "$TARGET_LOCATION"
much clear and simpler
A possibility:
#!/bin/bash
BUCKET_NAME="testbucket"
OBJECT_NAME="testworkflow-2.0.1.jar"
TARGET_LOCATION="/opt/test/testworkflow-2.0.1.jar
# one line
JSON_STRING='{"bucketname":"'"$BUCKET_NAME"'","objectname":"'"$OBJECT_NAME"'","targetlocation":"'"$TARGET_LOCATION"'"}'
# multi-line
JSON_STRING="{
\"bucketname\":\"${BUCKET_NAME}\",
\"objectname\":\"${OBJECT_NAME}\",
\"targetlocation\":\"${TARGET_LOCATION}\"
}"
# [optional] validate the string is valid json
echo "${JSON_STRING}" | jq
In addition to chepner's answer, it's also possible to construct the object completely from args with this simple recipe:
BUCKET_NAME=testbucket
OBJECT_NAME=testworkflow-2.0.1.jar
TARGET_LOCATION=/opt/test/testworkflow-2.0.1.jar
JSON_STRING=$(jq -n \
--arg bucketname "$BUCKET_NAME" \
--arg objectname "$OBJECT_NAME" \
--arg targetlocation "$TARGET_LOCATION" \
'$ARGS.named')
Explanation:
--null-input | -n disabled reading input. From the man page: Don't read any input at all! Instead, the filter is run once using null as the input. This is useful when using jq as a simple calculator or to construct JSON data from scratch.
--arg name value passes values to the program as predefined variables: value is available as $name. All named arguments are also available as $ARGS.named
Because the format of $ARGS.named is already an object, jq can output it as is.
First, don't use ALL_CAPS_VARNAMES: it's too easy to accidentally overwrite a crucial shell variable (like PATH)
Mixing single and double quotes in shell strings can be a hassle. In this case, I'd use printf:
bucket_name=testbucket
object_name=testworkflow-2.0.1.jar
target_location=/opt/test/testworkflow-2.0.1.jar
template='{"bucketname":"%s","objectname":"%s","targetlocation":"%s"}'
json_string=$(printf "$template" "$BUCKET_NAME" "$OBJECT_NAME" "$TARGET_LOCATION")
echo "$json_string"
For homework, read this page carefully: Security implications of forgetting to quote a variable in bash/POSIX shells
A note on creating JSON with string concatenation: there are edge cases. For example, if any of your strings contain double quotes, you can broken JSON:
$ bucket_name='a "string with quotes"'
$ printf '{"bucket":"%s"}\n' "$bucket_name"
{"bucket":"a "string with quotes""}
Do do this more safely with bash, we need to escape that string's double quotes:
$ printf '{"bucket":"%s"}\n' "${bucket_name//\"/\\\"}"
{"bucket":"a \"string with quotes\""}
I had to work out all possible ways to deal json strings in a command request, Please look at the following code to see why using single quotes can fail if used incorrectly.
# Create Release and Tag commit in Github repository
# returns string with in-place substituted variables
json=$(cat <<-END
{
"tag_name": "${version}",
"target_commitish": "${branch}",
"name": "${title}",
"body": "${notes}",
"draft": ${is_draft},
"prerelease": ${is_prerelease}
}
END
)
# returns raw string without any substitutions
# single or double quoted delimiter - check HEREDOC specs
json=$(cat <<-!"END" # or 'END'
{
"tag_name": "${version}",
"target_commitish": "${branch}",
"name": "${title}",
"body": "${notes}",
"draft": ${is_draft},
"prerelease": ${is_prerelease}
}
END
)
# prints fully formatted string with substituted variables as follows:
echo "${json}"
{
"tag_name" : "My_tag",
"target_commitish":"My_branch"
....
}
Note 1: Use of single vs double quotes
# enclosing in single quotes means no variable substitution
# (treats everything as raw char literals)
echo '${json}'
${json}
echo '"${json}"'
"${json}"
# enclosing in single quotes and outer double quotes causes
# variable expansion surrounded by single quotes(treated as raw char literals).
echo "'${json}'"
'{
"tag_name" : "My_tag",
"target_commitish":"My_branch"
....
}'
Note 2: Caution with Line terminators
Note the json string is formatted with line terminators such as LF \n
or carriage return \r(if its encoded on windows it contains CRLF \r\n)
using (translate) tr utility from shell we can remove the line terminators if any
# following code serializes json and removes any line terminators
# in substituted value/object variables too
json=$(echo "$json" | tr -d '\n' | tr -d '\r' )
# string enclosed in single quotes are still raw literals
echo '${json}'
${json}
echo '"${json}"'
"${json}"
# After CRLF/LF are removed
echo "'${json}'"
'{ "tag_name" : "My_tag", "target_commitish":"My_branch" .... }'
Note 3: Formatting
while manipulating json string with variables, we can use combination of ' and " such as following, if we want to protect some raw literals using outer double quotes to have in place substirution/string interpolation:
# mixing ' and "
username=admin
password=pass
echo "$username:$password"
admin:pass
echo "$username"':'"$password"
admin:pass
echo "$username"'[${delimiter}]'"$password"
admin[${delimiter}]pass
Note 4: Using in a command
Following curl request already removes existing \n (ie serializes json)
response=$(curl -i \
--user ${username}:${api_token} \
-X POST \
-H 'Accept: application/vnd.github.v3+json' \
-d "$json" \
"https://api.github.com/repos/${username}/${repository}/releases" \
--output /dev/null \
--write-out "%{http_code}" \
--silent
)
So when using it for command variables, validate if it is properly formatted before using it :)
If you need to build a JSON representation where members mapped to undefined or empty variables should be ommited, then jo can help.
#!/bin/bash
BUCKET_NAME=testbucket
OBJECT_NAME=""
JO_OPTS=()
if [[ ! "${BUCKET_NAME}x" = "x" ]] ; then
JO_OPTS+=("bucketname=${BUCKET_NAME}")
fi
if [[ ! "${OBJECT_NAME}x" = "x" ]] ; then
JO_OPTS+=("objectname=${OBJECT_NAME}")
fi
if [[ ! "${TARGET_LOCATION}x" = "x" ]] ; then
JO_OPTS+=("targetlocation=${TARGET_LOCATION}")
fi
jo "${JO_OPTS[#]}"
The output of the commands above would be just (note the absence of objectname and targetlocation members):
{"bucketname":"testbucket"}
can be done following way:
JSON_STRING='{"bucketname":"'$BUCKET_NAME'","objectname":"'$OBJECT_NAME'","targetlocation":"'$TARGET_LOCATION'"}'
For Node.js Developer, or if you have node environment installed, you can try this:
JSON_STRING=$(node -e "console.log(JSON.stringify({bucketname: $BUCKET_NAME, objectname: $OBJECT_NAME, targetlocation: $TARGET_LOCATION}))")
Advantage of this method is you can easily convert very complicated JSON Object (like object contains array, or if you need int value instead of string) to JSON String without worrying about invalid json error.
Disadvantage is it's relying on Node.js environment.
These solutions come a little late but I think they are inherently simpler that previous suggestions (avoiding the complications of quoting and escaping).
BUCKET_NAME=testbucket
OBJECT_NAME=testworkflow-2.0.1.jar
TARGET_LOCATION=/opt/test/testworkflow-2.0.1.jar
# Initial unsuccessful solution
JSON_STRING='{"bucketname":"$BUCKET_NAME","objectname":"$OBJECT_NAME","targetlocation":"$TARGET_LOCATION"}'
echo $JSON_STRING
# If your substitution variables have NO whitespace this is sufficient
JSON_STRING=$(tr -d [:space:] <<JSON
{"bucketname":"$BUCKET_NAME","objectname":"$OBJECT_NAME","targetlocation":"$TARGET_LOCATION"}
JSON
)
echo $JSON_STRING
# If your substitution variables are more general and maybe have whitespace this works
JSON_STRING=$(jq -c . <<JSON
{"bucketname":"$BUCKET_NAME","objectname":"$OBJECT_NAME","targetlocation":"$TARGET_LOCATION"}
JSON
)
echo $JSON_STRING
#... A change in layout could also make it more maintainable
JSON_STRING=$(jq -c . <<JSON
{
"bucketname" : "$BUCKET_NAME",
"objectname" : "$OBJECT_NAME",
"targetlocation" : "$TARGET_LOCATION"
}
JSON
)
echo $JSON_STRING
To build upon Hao's answer using NodeJS: you can split up the lines, and use the -p option which saves having to use console.log.
JSON_STRING=$(node -pe "
JSON.stringify({
bucketname: process.env.BUCKET_NAME,
objectname: process.env.OBJECT_NAME,
targetlocation: process.env.TARGET_LOCATION
});
")
An inconvenience is that you need to export the variables beforehand, i.e.
export BUCKET_NAME=testbucket
# etc.
Note: You might be thinking, why use process.env? Why not just use single quotes and have bucketname: '$BUCKET_NAME', etc so bash inserts the variables? The reason is that using process.env is safer - if you don't have control over the contents of $TARGET_LOCATION it could inject JavaScript into your node command and do malicious things (by closing the single quote, e.g. the $TARGET_LOCATION string contents could be '}); /* Here I can run commands to delete files! */; console.log({'a': 'b. On the other hand, process.env takes care of sanitising the input.
You could use envsubst:
export VAR="some_value_here"
echo '{"test":"$VAR"}' | envsubst > json.json
also it might be a "template" file:
//json.template
{"var": "$VALUE", "another_var":"$ANOTHER_VALUE"}
So after you could do:
export VALUE="some_value_here"
export ANOTHER_VALUE="something_else"
cat json.template | envsubst > misha.json
For a general case of building JSON from bash with arbitrary inputs, many of the previous responses (even the high voted ones with jq) omit cases when the variables contain " double quote, or \n newline escape string, and you need complex string concatenation of the inputs.
When using jq you need to printf %b the input first to get the \n converted to real newlines, so that once you pass through jq you get \n back and not \\n.
I found this with version with nodejs to be quite easy to reason about if you know javascript/nodejs well:
TITLE='Title'
AUTHOR='Bob'
JSON=$( TITLE="$TITLE" AUTHOR="$AUTHOR" node -p 'JSON.stringify( {"message": `Title: ${process.env.TITLE}\n\nAuthor: ${process.env.AUTHOR}`} )' )
It's a bit verbose due to process.env. but allows to properly pass the variables from shell, and then format things inside (nodejs) backticks in a safe way.
This outputs:
printf "%s\n" "$JSON"
{"message":"Title: Title\n\nAuthor: Bob"}
(Note: when having a variable with \n always use printf "%s\n" "$VAR" and not echo "$VAR", whose output is platform-dependent! See here for details)
Similar thing with jq would be
TITLE='Title'
AUTHOR='Bob'
MESSAGE="Title: ${TITLE}\n\nAuthor: ${AUTHOR}"
MESSAGE_ESCAPED_FOR_JQ=$(printf %b "${MESSAGE}")
JSON=$( jq '{"message": $jq_msg}' --arg jq_msg "$MESSAGE_ESCAPED_FOR_JQ" --null-input --compact-output --raw-output --monochrome-output )
(the last two params are not necessary when running in a subshell, but I just added them so that the output is then same when you run the jq command in a top-level shell).
Bash will not insert variables into a single-quote string. In order to get the variables bash needs a double-quote string.
You need to use double-quote string for the JSON and just escape double-quote characters inside JSON string.
Example:
#!/bin/sh
BUCKET_NAME=testbucket
OBJECT_NAME=testworkflow-2.0.1.jar
TARGET_LOCATION=/opt/test/testworkflow-2.0.1.jar
JSON_STRING="{\"bucketname\":\"$BUCKET_NAME\",\"objectname\":\"$OBJECT_NAME\",\"targetlocation\":\"$TARGET_LOCATION\"}"
echo $JSON_STRING
if you have node.js and get minimist installed in global:
jc() {
node -p "JSON.stringify(require('minimist')(process.argv), (k,v) => k=='_'?undefined:v)" -- "$#"
}
jc --key1 foo --number 12 --boolean \
--under_score 'abc def' --'white space' ' '
# {"key1":"foo","number":12,"boolean":true,"under_score":"abc def","white space":" "}
you can post it with curl or what:
curl --data "$(jc --type message --value 'hello world!')" \
--header 'content-type: application/json' \
http://server.ip/api/endpoint
be careful that minimist will parse dot:
jc --m.room.member #gholk:ccns.io
# {"m":{"room":{"member":"#gholk:ccns.io"}}}
Used this for AWS Macie configuration:
JSON_CONFIG=$( jq -n \
--arg bucket_name "$BUCKET_NAME" \
--arg kms_key_arn "$KMS_KEY_ARN" \
'{"s3Destination":{"bucketName":$bucket_name,"kmsKeyArn":$kms_key_arn}}'
)
aws macie2 put-classification-export-configuration --configuration "$JSON_CONFIG"
You can simply make a call like this to print the JSON.
#!/bin/sh
BUCKET_NAME=testbucket
OBJECT_NAME=testworkflow-2.0.1.jar
TARGET_LOCATION=/opt/test/testworkflow-2.0.1.jar
echo '{ "bucketName": "'"$BUCKET_NAME"'", "objectName": "'"$OBJECT_NAME"'", "targetLocation": "'"$TARGET_LOCATION"'" }'
or
JSON_STRING='{ "bucketName": "'"$BUCKET_NAME"'", "objectName": "'"$OBJECT_NAME"'", "targetLocation": "'"$TARGET_LOCATION"'" }'
echo $JOSN_STRING
I want to replace some text in a variable by another variable.
body='{ "server": {
"metadata": "metaToReplace"
}
}'
meta="{
ARTS_ORACLE_INT_IP: 10.120.47.151,
ARTS_USER: performance
}"
I tried this, but didn't work:
body=$(echo "${body}" | sed "s|\"metaToReplace\"|${meta}|g")
I got this error :
sed: -e expression #1, char 19: unterminated `s' command
The newlines in the replacement variable are wrecking the syntax of the s/// command:
$ echo "${body}" | sed "s|\"metaToReplace\"|${meta}|g"
sed: -e expression #1, char 19: unterminated `s' command
I'd use awk: You can transfer the contents of the shell variable to an awk variable:
body=$( awk -v rep="$meta" '{gsub(/"metaToReplace"/, rep); print}' <<< "$body" )
The problem is that the double quotes aren't being put into the body string. Since you started the string with double quotes, the inner quotes are simply matching that and ending the string. Use single quotes around it so that the inner quotes will be treated literally, rather than as delimiters.
body='{ "server": {
"metadata": "metaToReplace"
}
}'
You can do this:
meta="$(echo "$meta" |sed ':a;N;s/\n/\\n/;ta;')"
body=$(echo "${body}" | sed "s|\"metaToReplace\"|$meta|g")
echo "$body"
Output:
{ "server": {
"metadata": {
ARTS_ORACLE_INT_IP: 10.120.47.151,
ARTS_USER: performance
}
}
}
How it works:
echo "$meta" |sed ':a;N;s/\n/\\n/;ta;'
replaces all newlines in meta to leteral \n and thus meta becomes a single line string:
{\n ARTS_ORACLE_INT_IP: 10.120.47.151,\n ARTS_USER: performance\n}
which is then used as a replace string and in replacement, \n is interpreted as new line again.