Complex MongoDB syntax in Linux Shell script

Question

I have created a CRON job that takes backup of database everyday.

The script has a command of Mongodump with a condition to dump the records that are 7 days old.

The script runs fine until I added the --query parameter into the mongodump command.

mongodump [host, port and dbparams] --query "{_id: {\$lt: ObjectId(Math.floor(new Date(Date.now() - 86400000*7)/1000).toString(16) + '0000000000000000')}}"

An error thrown because of the --query, which says:

assertion: 16619 code FailedToParse: FailedToParse: Expecting quoted string: offset:21

So what is the correct way to integrate this query into the script?

@OneOfOne Nope, the '$lt' without '\' gives error 'First character in field must be [A-Za-z$_]: offset:7'. I have added '\' to escape the $ . — sohel khalifa
– sohel khalifa, Commented Nov 1, 2013 at 13:07
@sohelkhalifa can we run the scripts without having mongo shell installed in machine? — Ravi Teja Muddada
– Ravi Teja Muddada, Commented Aug 21, 2021 at 6:35

Bruce Lucas · Accepted Answer · 2013-11-01 14:14:46Z

2

You could compute the date string using the shell and then pass that into the --query option. Here is your original Javascript expression and the equivalent computation in the shell:

$ mongo --eval "Math.floor(new Date(Date.now() - 86400000*7)/1000).toString(16) + '0000000000000000'"
526a7ac00000000000000000
$ printf '%x0000000000000000' $(($(date +%s) - 86400*7))
526a7ac00000000000000000

You would then use this in a short script such as the following:

now=$(printf '%x0000000000000000' $(($(date +%s) - 86400*7)))
mongodump --query "{_id: {\$lt: '$now'}}"

Hope this helps,

Bruce

answered Nov 1, 2013 at 14:14

Bruce Lucas

9595 silver badges5 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Rafa Viotti Over a year ago

Bruce's solution, a little simpler: printf '%x0000000000000000' $(date --date='7 days ago' +%s)

Bruce Lucas Over a year ago

Good improvement Rafa.

Collectives™ on Stack Overflow

Complex MongoDB syntax in Linux Shell script

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related