CODEWITHSUNDEEP
mongodbmongo-shellmongosh
fgalan
fgalan

Reputation: 12322

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.

Upvotes: 0

Views: 221

Answers (2)

Alex Blex
Alex Blex

Reputation: 37108

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' }

Upvotes: 1

Wernfried Domscheit
Wernfried Domscheit

Reputation: 59592

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)>

Upvotes: 1

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