Mongo query works in mongo shell but not in a bash mongo --eval? - mongodb

Question

Here is an example query:
db.readings.find( {"_id.s" : ISODate("2012-11-01T00:05:00Z") } ).count()
Query works in the mongo shell. However, in a bash script or directly in the Ubuntu shell
mongo fivemin --eval "printjson(db.readings.find( {"_id.s" : ISODate("2012-11-01T00:05:00Z") } ).count())"
returns a SyntaxError: missing : after property id (shell eval):1
I can't seem to find a problem with the query. I reverted to { "_id" : {"s" : ...} }, and it still gives the same problem. find().count() works however.

Answer 1

Had the same issue in bash shell.
This will fail because of double quotes:
mongo fivemin --eval "printjson(db.readings.find( {"_id.s" : ISODate("2012-11-01T00:05:00Z") } ).count())"
But using the eval string in single quote it works:
mongo fivemin --eval 'printjson(db.readings.find( {"_id.s" : ISODate("2012-11-01T00:05:00Z") } ).count())'
And if you use a $ sign like $regex you need to escape it:
mongo fivemin --eval 'printjson(db.readings.find( {"_id.s" : {"\$regex":"2012-11-01T*"} } ).count())'

Answer 2

use single quotes into double,
e.g.:
mongo fivemin --eval "printjson(db.readings.find( {'_id.s' : ISODate('2012-11-01T00:05:00Z') } ).count())"

Answer 3

There is also another possible issue using --eval with bash double quotes, if the query contains mongo operators i.e. $ne, $gt etc, since operators start with $.
double quotes:
$ echo " '$ne': null "
$ => '': null
single quotes:
$ echo ' "$ne": null '
$ => "$ne": null
Bash tries to replace these operators with variables.
$ ne = 'test'
$ echo " '$ne': null "
$ => 'test': null
So, I always recommend to use --eval with single quotes.

Answer 4

Just sat and thought about it. It seems to be a problem with bash exiting out on the " (should have noticed immediately!). Instead I used ' (or I guess you can use /" for JSON) so the query looks like:
printjson(db.readings.find({'_id.s' : ISODate('2013-01-01T00:05:00Z') }).count())"

Answer 5

The best way to handle this is to build the mongo command in a var. Then use eval command to execute the mongo command:
mongo_update_query="db.collectionName.update({ name:\""${some_name}"\", \
{ \$addToSet: { nick_names : { \$each : [ ${name_array} ] }}});"
mongo_cmd_str=$(echo "mongo --host ${mongo_host} --port ${mongo_port} ${mongo_database} --eval '${mongo_update_query}'")
# the actual call to mongo query
eval ${mongo_cmd_str}