I found several errors in your approach, let's examine them one by one.
Date format
MongoDB expects date to be a number or ISO 8601 string.
Unfortunately, unix date utility have no build-in support for this format, so you should use:
d=`date --date="-3 month" -u +"%Y-%m-%dT%H:%M:%SZ"`
Using extended JSON
JSON specification have no support for dates, so you should use MongoDB extended JSON. So, your final query should look like this:
{ "timeCreated": { "$lte": { "$date": "2014-05-12T08:53:29Z" } } }
test.sh output
You messed up with quotation marks. Here is a script example, outputting correct JSON:
#!/bin/bash
d=`date --date="-3 month" -u +"%Y-%m-%dT%H:%M:%SZ"`
echo '{ "timeCreated": { "$lte": { "$date": "'$d'" } } }'
Passing query to mongoexport
mongoexport expects --query to be a JSON string, not .sh script. So, when you're passing file path to --query, mongoexport expects it to be a JSON file.
To fix it you should execute test2.sh yourself and pass resulting string to mongoexport:
mongoexport --db game_server --collection GameHistory \
--query "`./test2.sh`" --out ./test2.json
N.B. Notice " quotation marks around ./test2.sh call. They're telling bash to treat ./test2.sh output as a single parameter, ignoring all inner quotation marks and whitespaces.
