Question 304826 in Mongodb Question posted in
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Can mongosh (new MongoDB shell) produce the same output format than mongo (legacy MongoDB shell)?

The following command executed with legacy mongo shell:

mongo --quiet << EOF
  show dbs
EOF

provides this output

admin   0.000GB
config  0.000GB
local   0.000GB

However, the same command with new shell (mongosh)

$ mongosh --quiet << EOF
  show dbs
EOF

provides a slightly different ouput:

test>   show dbs
admin   40.00 KiB
config  36.00 KiB
local   40.00 KiB
test>

I have a set of old script using mongo that I want to migrate to mongosh but that slight difference in the output makes them break in some point. I wonder if I could avoid extra work adapting it configuring mongosh to provide output in the exact same way than mongo.

Is there some way of doing so, please?

Thanks in advance!

EDIT: the show db above is just an example. I’m looking for a general solution that covers in general any other case. For instance, this new one:

Legacy shell:

$ echo 'db.dropDatabase()' | mongo sample-db --quiet
{ "ok" : 1 }

New shell:

$ echo 'db.dropDatabase()' | mongosh sample-db --quiet
sample-db> db.dropDatabase()
{ ok: 1, dropped: 'sample-db' }
sample-db>

In fact, just the ability of removing the prompt part that output (test>, sample-db>, etc.) would help a lot.

Tags:

2

Answers


  1. 0

    show dbs is a shell internal command, thus it would be difficult.

    Some commands from legacy mongo shell you can get by loading mongocompat. You can add this to your .mongoshrc.js

    load('.../index.js');

    To get all databases you can also query collection db.getSiblingDB('config').databases

    Try

    db.getSiblingDB('config').databases.find({}).forEach(x => {
   print(`${x._id} ${db.getSiblingDB(x._id).stats(1000 * 1000 * 1000).storageSize}GB`)
})

    It should produce the same output as show dbs

    For your problem, better use

    mongosh --quiet --nodb --eval 'print("Hello World")'
Hello World

    instead of

    echo 'print("Hello World")' | mongosh --quiet --nodb 
(NoDB)> print("Hello World")
Hello World

(NoDB)>
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  2. 0

    There is eval parameter for that.

    Instead of

    $ echo 'db.dropDatabase()' | mongosh sample-db --quiet

    Do

    $ mongosh sample-db --quiet --eval 'db.dropDatabase()'

    It outputs exactly

    { ok: 1, dropped: 'sample-db' }
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