$ cat tmp/foo.js db.foo.drop(); db.foo.insert({ foo: 'bar' }); db.foo.insert({ foo: 'bar' }); db.foo.createIndex({ foo: 1 }, { unique: true }); db.foo.getIndexes(); $ mongo tmp/foo.js MongoDB shell version: 3.2.18 connecting to: test $ echo $? 0 $ mongo < tmp/foo.js MongoDB shell version: 3.2.18 connecting to: test true WriteResult({ "nInserted" : 1 }) WriteResult({ "nInserted" : 1 }) { "ok" : 0, "errmsg" : "E11000 duplicate key error index: test.foo.$foo_1 dup key: { : \"bar\" }", "code" : 11000 } [ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "test.foo" } ] bye $ echo $? 0