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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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