embed bash variable in mongodb query

Question

I have a bash variable $i which has to be embed in mongo shell query to get the data by comparing date.

i=10
while [  "$i" -lt 12 ]; do
        mongo $MONGO_DATABASE --eval 'printjson(db.mycollection.find({"created_at":{"$lte":ISODate(2016-04-\"$i\"T09:26:31.190Z)}}).toArray())' > $OUTPUT_DIRECTORY/$FILE_NAME  
done

The above implementation is giving i: command not found

Tom Fenech · Accepted Answer · 2016-07-13 10:47:29Z

1

Shell variables aren't expanded within single quotes. Use double quotes:

mongo "$MONGO_DATABASE" --eval "printjson...ISODate(2016-04-${i}T09:26:31.190Z)

You will then need to escape your usages of double quotes within the string that you are evaluating, e.g. \"created_at\". You will also need to escape other usages of $, e.g. \$lte.

Alternatively, you can use single quotes around the whole command and then use something like this:

mongo "$MONGO_DATABASE" --eval 'printjson...ISODate(2016-04-'"$i"'T09:26:31.190Z)

i.e. close the single quotes, concatenate the shell variable (inside double quotes), then reopen the single quotes.

edited Jul 13, 2016 at 10:47

answered Jul 13, 2016 at 10:03

Tom Fenech

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