How to write string (const char*) to ESP32 NVS

Also see: How to read string (const char*) from ESP32 NVS

You can use this utility function to write a string (const char*) into the NVS:

bool _NVS_WriteString(nvs_handle_t nvs, const char* key, const char* value) {
    esp_err_t err;
    if((err = nvs_set_str(nvs, key, value)) != ESP_OK) {
        Serial.printf("Failed to write NVS key %s: %s\r\n", key, esp_err_to_name(err));
        return false;
    }
    return true;
}

Usage example

This example is based on How to initialize NVS on ESP32. Most importantly, it assumes you have already initialized the NVS and myNVS exists and is valid.

char mySerialNo[128] = {0};

_NVS_WriteString(myNVS, "SerialNo", "0000001");

This will write the value 0000001 to the NVS with key SerialNo

Note that NVS strings are length-delimited (as in: The length is stored in the NVS) and not neccessarily NUL-terminated. This code does not store the NUL terminator in NVS.