tencent cloud


Checking Whether Objects Exist

Last updated: 2022-01-23 14:17:47


    This document provides an overview of the API and sample code for quickly checking whether an object exists in a bucket.

    API Operation Description
    HEAD Object Querying object metadata Queries the metadata of an object

    Checking Whether an Object Exists


    This API is used to check whether an object exists in a bucket. It actually calls the HEAD Object API to perform the action.

    Method prototype

    cos_status_t *cos_check_object_exist(const cos_request_options_t *options, 
                                       const cos_string_t *bucket, 
                                       const cos_string_t *object,
                                       cos_table_t *headers, 
                                       cos_object_exist_status_e *object_exist,
                                       cos_table_t **resp_headers);

    Parameter description

    Parameter Description Type
    options COS request options Struct
    bucket Bucket name in the format of BucketName-APPID String
    object Object name String
    headers Additional headers of a COS request Struct
    object_exist Whether an object exists. Enumerated values: exist, non exist, unknown (no explicit state is obtained) Enum
    resp_headers Returns the HTTP response headers Struct

    Response description

    Response Parameter Description Type
    code Error code Int
    error_code Error code content String
    error_msg Error code description String
    req_id Request message ID String


    #include "cos_http_io.h"
    #include "cos_api.h"
    #include "cos_log.h"
    // `endpoint` is the COS access domain name. For more information, see https://www.tencentcloud.com/document/product/436/6224.
    static char TEST_COS_ENDPOINT[] = "cos.ap-guangzhou.myqcloud.com";
    // A developer-owned secret ID/key used for the project. It can be obtained at https://console.tencentcloud.com/cam/capi.
    static char *TEST_ACCESS_KEY_ID;                // Your SecretId
    static char *TEST_ACCESS_KEY_SECRET;            // Your SecretKey
    // A unique user-level resource identifier for COS access. It can be obtained at https://console.tencentcloud.com/cam/capi.
    static char TEST_APPID[] = "<APPID>";    // Your APPID
    // COS bucket name, in the format of [bucket]-[appid], for example `mybucket-1253666666`. It can be obtained at https://console.tencentcloud.com/cos5/bucket.
    static char TEST_BUCKET_NAME[] = "<bucketname-appid>";  
    // A unique identifier of an object stored in COS. For more information about objects and object keys, please see https://www.tencentcloud.com/document/product/436/13324.
    static char TEST_OBJECT_NAME1[] = "1.txt";
    void log_status(cos_status_t *s)
      cos_warn_log("status->code: %d", s->code);
      if (s->error_code) cos_warn_log("status->error_code: %s", s->error_code);
      if (s->error_msg) cos_warn_log("status->error_msg: %s", s->error_msg);
      if (s->req_id) cos_warn_log("status->req_id: %s", s->req_id);
    void init_test_config(cos_config_t *config, int is_cname)
      cos_str_set(&config->endpoint, TEST_COS_ENDPOINT);
      cos_str_set(&config->access_key_id, TEST_ACCESS_KEY_ID);
      cos_str_set(&config->access_key_secret, TEST_ACCESS_KEY_SECRET);
      cos_str_set(&config->appid, TEST_APPID);
      config->is_cname = is_cname;
    void init_test_request_options(cos_request_options_t *options, int is_cname)
      options->config = cos_config_create(options->pool);
      init_test_config(options->config, is_cname);
      options->ctl = cos_http_controller_create(options->pool, 0);
    void test_check_object_exist()
      cos_pool_t *p = NULL;
      int is_cname = 0;
      cos_status_t *s = NULL;
      cos_request_options_t *options = NULL;
      cos_string_t bucket;
      cos_string_t object;
      cos_table_t *resp_headers;
      cos_table_t *headers = NULL;
      cos_object_exist_status_e object_exist;
       cos_pool_create(&p, NULL);
      options = cos_request_options_create(p);
      init_test_request_options(options, is_cname);
      cos_str_set(&bucket, TEST_BUCKET_NAME);
      cos_str_set(&object, TEST_OBJECT_NAME1);
       // Check whether an object exists
      s = cos_check_object_exist(options, &bucket, &object, headers, &object_exist, &resp_headers);
      if (object_exist == COS_OBJECT_NON_EXIST) {
          printf("object: %.*s non exist.\n", object.len, object.data);
      } else if (object_exist == COS_OBJECT_EXIST) {
          printf("object: %.*s exist.\n", object.len, object.data);
      } else {
          printf("object: %.*s unknown status.\n", object.len, object.data);
    int main(int argc, char *argv[])
      // Get SecretId and SecretKey from environment variables
      TEST_ACCESS_KEY_ID     = getenv("COS_SECRETID");
        if (cos_http_io_initialize(NULL, 0) != COSE_OK) {
       // Set the log level. Default value: `COS_LOG_WARN`
       // Set log output. Default value: `stderr`
       return 0;
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