mongodb 搜索结果保存到文件中
mongo localhost:11111/test -u *** -p **** --quiet --eval "db.collections1.find({image_url: { $regex: '43.12'}}, {image_url: 1, id: 1}).sort({id: -1}).forEach(printjson);" > 1.txt


http://docs.mongodb.org/manual/tutorial/write-scripts-for-the-mongo-shell/#mongo-shell-new-connections