Because the output of the upgradeCheck() helper can be potentially very long, it makes sense to pipe output to a file rather than in the shell directly.

We should include something like the following example:

To connect to the admin database on localhost and use secondary:

# ./mongo --eval "db.getMongo().setSlaveOk();
                db.upgradeCheckAllDbs()" localhost/admin | tee /tmp/upgradecheck.txt

To connect to the myDb database and check the myColl collection on localhost of a primary, standalone or mongos:

# ./mongo --eval "db.upgradeCheck({collection:'myColl')" 
                 localhost/myDb | tee /tmp/upgradecheck.txt