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Querying Object Metadata
Last updated: 2024-02-01 18:01:21
Querying Object Metadata
Last updated: 2024-02-01 18:01:21

Overview

This document provides an overview of APIs and SDK code samples related to querying object metadata.
API
Operation
Description
Querying object metadata
Queries the metadata of an object

Querying Object Metadata

Description

This API is used to query the metadata of an object.

Method prototype

cos_status_t *cos_head_object(const cos_request_options_t *options,
const cos_string_t *bucket,
const cos_string_t *object,
cos_table_t *headers,
cos_table_t **resp_headers);

Parameter description

Parameter
Description
Type
options
COS request options
Struct
bucket
Bucket name in the format: BucketName-APPID
String
object
Object name
String
headers
Additional headers of a COS request
Struct
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

Sample

#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";

static void print_headers(cos_table_t *headers)
{
const cos_array_header_t *tarr;
const cos_table_entry_t *telts;
int i = 0;

if (apr_is_empty_table(headers)) {
return;
}

tarr = cos_table_elts(headers);
telts = (cos_table_entry_t*)tarr->elts;

printf("headers:\\n");
for (; i < tarr->nelts; i++) {
telts = (cos_table_entry_t*)(tarr->elts + i * tarr->elt_size);
printf("%s: %s\\n", telts->key, telts->val);
}
}

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_head_object()
{
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 = NULL;

// Create a memory pool
cos_pool_create(&p, NULL);

// Initialize the request options
options = cos_request_options_create(p);
init_test_request_options(options, is_cname);
cos_str_set(&bucket, TEST_BUCKET_NAME);

// Get object metadata
cos_str_set(&object, TEST_OBJECT_NAME1);
s = cos_head_object(options, &bucket, &object, NULL, &resp_headers);
print_headers(resp_headers);
if (cos_status_is_ok(s)) {
printf("head object succeeded\\n");
} else {
printf("head object failed\\n");
}

// Destroy the memory pool.
cos_pool_destroy(p);
}

int main(int argc, char *argv[])
{
// Get SecretId and SecretKey from environment variables
TEST_ACCESS_KEY_ID = getenv("COS_SECRETID");
TEST_ACCESS_KEY_SECRET = getenv("COS_SECRETKEY");

if (cos_http_io_initialize(NULL, 0) != COSE_OK) {
exit(1);
}

// Set the log level. Default value: `COS_LOG_WARN`
cos_log_set_level(COS_LOG_WARN);

// Set log output. Default value: `stderr`
cos_log_set_output(NULL);

test_head_object();

cos_http_io_deinitialize();

return 0;
}
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