Elasticsearch not_analyzed field transform double '$' symbol - elasticsearch

Question

I have a problem when I include a double dollar sign symbol in a not analyzed field. When I check the mapping for the type with the following command:
curl -XGET 'http://localhost:9200/documents/_mapping/document'
I get this output for the code field:
{
"documents": {
"mappings": {
"document": {
"properties": {
"code": {
"index": "not_analyzed",
"type": "string"
},
// More field mappings
If I test the mapping with the following command:
curl -XGET 'http://localhost:9200/documents/_analyze?field=code' -d "ABC$"
I get the following output:
{"tokens":[{"token":"ABC$","start_offset":0,"end_offset":4,"type":"word","position":1}]}
This is ok because the token has the same value that the data entered in the command. The problem is when I use a double dollar sign like this:
 curl -XGET 'http://localhost:9200/documents/_analyze?field=code' -d "ABC$$"
Then I get the following token:
{"tokens":[{"token":"ABC4088","start_offset":0,"end_offset":7,"type":"word","position":1}]}
It looks like the double dollar sign gets replaced by the number 4088. According to the docs, the not_analyzed index attribute means:
Index this field, so it is searchable, but index the value exactly as specified. Do not analyze it.
Do miss something in the code field mapping to avoid this?

Answer 1

This is because $$ is a special environment variable in your shell that gets expanded to the ID of the current shell process.
So when running the curl command what happens is that the PID of your current shell is resolved and replaces the $$ variable, hence the 4088 you see instead of $$.
Try to issue echo $$ and you'll see the ID of your current shell.
curl -XGET 'http://localhost:9200/documents/_analyze?field=code' -d "ABC4088"
^
|
$$ replaced by the ID of your process
Try to simply escape the $ characters and you should be fine
curl -XGET 'http://localhost:9200/documents/_analyze?field=code' -d "ABC\$\$"