This example demonstrates the usage of obtaining and interpreting statistics about the a given NVS partition, namely free/used/available/total entries and namespace count.

The default "nvs" partition is first erased, then a mock string data configuration is written to 2 different namespaces, followed by checking the changed statistics and mainly the number of newly used NVS entries.

Statistics obtained via nvs_get_stats() are the following:


`available entries`	Essential statistic, specifies free non-reserved entries available for data storage.
`used entries`	Includes 1 overhead entry per namespace + actual data entries used by data storage.
`free entries`	Free entries are both the free available to the user entries, and free but internally reserved (not available to the user).
`total entries`	Number of all entries (free + used).

Detailed functional description of NVS and API is provided in documentation.

How to use example

Hardware required

This example does not require any special hardware, and can be run on any common development board.

Build and flash

Build the project and flash it to the board, then run monitor tool to view serial output:

idf.py -p PORT flash monitor

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

Example Output

...
I (265) nvs_statistics_example: Erasing the contents of the default NVS partition...
I (475) nvs_statistics_example: Opening Non-Volatile Storage (NVS) handle for namespace '_mock_data'...
I (485) nvs_statistics_example: Getting NVS statistics...
I (485) nvs_statistics_example: NVS statistics:
I (485) nvs_statistics_example: Used NVS entries: 1
I (485) nvs_statistics_example: Free NVS entries: 755
I (495) nvs_statistics_example: Available NVS entries: 629
I (495) nvs_statistics_example: Total NVS entries: 756
I (505) nvs_statistics_example: Namespace count: 1
I (505) nvs_statistics_example: Writing mock data key-value pairs to NVS namespace '_mock_data'...
I (525) nvs_statistics_example: Committing data in NVS namespace '_mock_data'...
I (525) nvs_statistics_example: Getting post-commit NVS statistics...
I (525) nvs_statistics_example: NVS statistics:
I (535) nvs_statistics_example: Used NVS entries: 30
I (535) nvs_statistics_example: Free NVS entries: 726
I (545) nvs_statistics_example: Available NVS entries: 600
I (545) nvs_statistics_example: Total NVS entries: 756
I (555) nvs_statistics_example: Namespace count: 1
I (555) nvs_statistics_example: Newly used entries match expectation.
I (565) nvs_statistics_example: Newly used entries: 29, expected: 29.
I (575) nvs_statistics_example: NVS handle for namespace '_mock_data' closed.
I (575) nvs_statistics_example: Opening Non-Volatile Storage (NVS) handle for namespace '_mock_data'...
I (585) nvs_statistics_example: Reading stored data from NVS namespace '_mock_data'...
I (595) nvs_statistics_example: Read key-value pair from NVS: 'wifi_ssid':'HomeNetwork'
I (605) nvs_statistics_example: Read key-value pair from NVS: 'wifi_pass':'MySecretPass'
I (605) nvs_statistics_example: Read key-value pair from NVS: 'dev_name':'LivingRoomThermostat'
I (615) nvs_statistics_example: Read key-value pair from NVS: 'temp_unit':'Celsius'
I (625) nvs_statistics_example: Read key-value pair from NVS: 'target_temp':'22'
I (635) nvs_statistics_example: Read key-value pair from NVS: 'eco_mode':'false'
I (635) nvs_statistics_example: Read key-value pair from NVS: 'fw_version':'1.2.3'
I (645) nvs_statistics_example: Read key-value pair from NVS: 'led_bright':'80'
I (655) nvs_statistics_example: Read key-value pair from NVS: 'auto_update':'true'
I (665) nvs_statistics_example: Read key-value pair from NVS: 'last_sync':'2025-01-01T08:00:00Z'
I (665) nvs_statistics_example: Read key-value pair from NVS: 'user_lang':'en'
I (675) nvs_statistics_example: Read key-value pair from NVS: 'long_token':'2f8c1e7b5a4d9c6e3b0f1a8e5d7c2b6f4e1a9c7b'
I (685) nvs_statistics_example: Read key-value pair from NVS: 'very_long_token':'7e2b1c9f5a4d8e3b0f1a6c7e2d9b5a4c8e1f7b2d6c3a9e5b0f1a8c7e2d9b5a4c8e1f7b2d6c3a9e5b'
I (705) nvs_statistics_example: NVS handle for namespace '_mock_data' closed.
I (705) nvs_statistics_example: Opening Non-Volatile Storage (NVS) handle for namespace '_mock_backup'...
I (715) nvs_statistics_example: Getting NVS statistics...
I (725) nvs_statistics_example: NVS statistics:
I (725) nvs_statistics_example: Used NVS entries: 31
I (735) nvs_statistics_example: Free NVS entries: 725
I (735) nvs_statistics_example: Available NVS entries: 599
I (745) nvs_statistics_example: Total NVS entries: 756
I (745) nvs_statistics_example: Namespace count: 2
I (755) nvs_statistics_example: Writing mock data key-value pairs to NVS namespace '_mock_backup'...
I (765) nvs_statistics_example: Committing data in NVS namespace '_mock_backup'...
I (765) nvs_statistics_example: Getting post-commit NVS statistics...
I (775) nvs_statistics_example: NVS statistics:
I (775) nvs_statistics_example: Used NVS entries: 60
I (785) nvs_statistics_example: Free NVS entries: 696
I (785) nvs_statistics_example: Available NVS entries: 570
I (795) nvs_statistics_example: Total NVS entries: 756
I (795) nvs_statistics_example: Namespace count: 2
I (805) nvs_statistics_example: Newly used entries match expectation.
I (805) nvs_statistics_example: Newly used entries: 29, expected: 29.
I (815) nvs_statistics_example: NVS handle for namespace '_mock_backup' closed.
I (825) nvs_statistics_example: Opening Non-Volatile Storage (NVS) handle for namespace '_mock_backup'...
I (835) nvs_statistics_example: Reading stored data from NVS namespace '_mock_backup'...
I (835) nvs_statistics_example: Read key-value pair from NVS: 'wifi_ssid':'HomeNetwork'
I (845) nvs_statistics_example: Read key-value pair from NVS: 'wifi_pass':'MySecretPass'
I (855) nvs_statistics_example: Read key-value pair from NVS: 'dev_name':'LivingRoomThermostat'
I (865) nvs_statistics_example: Read key-value pair from NVS: 'temp_unit':'Celsius'
I (865) nvs_statistics_example: Read key-value pair from NVS: 'target_temp':'22'
I (875) nvs_statistics_example: Read key-value pair from NVS: 'eco_mode':'false'
I (885) nvs_statistics_example: Read key-value pair from NVS: 'fw_version':'1.2.3'
I (895) nvs_statistics_example: Read key-value pair from NVS: 'led_bright':'80'
I (895) nvs_statistics_example: Read key-value pair from NVS: 'auto_update':'true'
I (905) nvs_statistics_example: Read key-value pair from NVS: 'last_sync':'2025-01-01T08:00:00Z'
I (915) nvs_statistics_example: Read key-value pair from NVS: 'user_lang':'en'
I (925) nvs_statistics_example: Read key-value pair from NVS: 'long_token':'2f8c1e7b5a4d9c6e3b0f1a8e5d7c2b6f4e1a9c7b'
I (935) nvs_statistics_example: Read key-value pair from NVS: 'very_long_token':'7e2b1c9f5a4d8e3b0f1a6c7e2d9b5a4c8e1f7b2d6c3a9e5b0f1a8c7e2d9b5a4c8e1f7b2d6c3a9e5b'
I (945) nvs_statistics_example: NVS handle for namespace '_mock_backup' closed.
I (955) nvs_statistics_example: Returning from app_main().
I (955) main_task: Returned from app_main()
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