Mongo eval arguments taken from a list bash script-CodePudding

I am working on a bash script and would like to have a for loop iterate over specific collections in mongo and perform a count. If any of these specific collections is non-zero, then break the loop.

I have initialize this variable inside my script (assume the connection is working):

MONGO_EVAL="mongo prod $MONGO_CONN_CONF --quiet --eval"

and also a list for specific collections (initialized above, at an early phase in the script):

db_collections=(collectionA collectionB collectionC....)

Then iterate over a for loop and count the documents on each collection.

 for str in ${db_collections[@]}; do
   $MONGO_EVAL 'db.$db_collections.count();'
 done

How do I do it the right way?

CodePudding user response：

Should be rather this:

db_collections=(collectionA collectionB collectionC....)

for str in ${db_collections[@]}; do
    mongo "$MONGO_CONN_CONF" --quiet --eval "db.${str}.count();"
done

for str in ${db_collections[@]}; do
    mongo "$MONGO_CONN_CONF" --quiet --eval "db.getCollection('${str}').count();"
done

mongo "$MONGO_CONN_CONF" --quiet --eval "for (let c of ['collectionA', 'collectionB', 'collectionC']) db.getCollection(c).count();"

Note, you have to use double quotes ("), otherwise ${str} is not replaced by variable value.

Regarding your actual problem "If any of these specific collections is non-zero, then break the loop" if could be like this:

for (let c of ['collectionA', 'collectionB', 'collectionC']) {
   let count = db.getCollection(c).count();
   if (count > 0) break;
}

Bear in mind, this loop actually does nothing, just count and potentially exit. I assume you would also need at least a print(c) or something similar.