argument list too long curl - bash

Question

Trying to solve "argument list too long"
I have been searching for a solution and found the closest one to my issue
curl: argument list too long
however the response is not clear as I am still having the issue "argument list too long"
curl -X POST -d #data.txt \
https://Path/to/attachments \
-H 'content-type: application/vnd.api+json' \
-H 'x-api-key: KEY' \
-d '{
"data": {
"type": "attachments",
"attributes": {
"attachment": {
"content": "'$(cat data.txt | base64 --wrap=0)'",
"file_name": "'"$FileName"'"
}
}
}
}'
thank you

Answer 1

Use jq to format your base64 encoded data string into a proper JSON string, and then pass the JSON data as standard input to the curl command.
#!/usr/bin/env sh
attached_file='img.png'
# Pipe the base64 encoded content of attached_file
base64 --wrap=0 "$attached_file" |
# into jq to make it a proper JSON string within the
# JSON data structure
jq --slurp --raw-input --arg FileName "$attached_file" \
'{
"type": "attachments",
"attributes": {
"attachment": {
"content": .,
"file_name": $FileName
}
}
}
' |
# Get the resultant JSON piped into curl
# that will read the data from the standard input
# using -d #-
curl -X POST -d #- \
'https://Path/to/attachments' \
-H 'content-type: application/vnd.api+json' \
-H 'x-api-key: KEY'

Answer 2

Per the linked answer
you are trying to pass the entirety of the base64'd content on the command line
This is a limitation of the shell, not curl. That is, the shell is responding with error argument list too long. The program curl is never even started.
The recommendation is
curl has the ability to load in data to POST from a file
Write the json data to some file /tmp/data.json using piping.(the commands will use piping | and file redirection > >> which can handle arbitrarily large amounts of data. Whereas, you cannot place arbitrarily large amounts of data into a single command, there is a limit).
echo -n '
{
"data": {
"type": "attachments",
"attributes": {
"attachment": {
"content": "' > /tmp/data.json
cat data.txt | base64 --wrap=0 >> /tmp/data.json
echo -n '",
"file_name": "'"$FileName"'"
}
}
}
}' >> /tmp/data.json
Pass that file path /tmp/data.json to the curl command using # so curl knows it's a file path.
curl -X POST -d #/tmp/data.json \
"https://Path/to/attachments" \
-H 'content-type: application/vnd.api+json' \
-H 'x-api-key: KEY'