Object Meta includes HTTP headers and user-defined Object Meta. For more information, see Object Meta in OSS Developer Guide.

Obtain Object Meta

After uploading files to OSS or before reading objects from OSS, you can use the oss_get_object_meta interface to obtain some of meta information about the objects, such as the length and type. Run the following code to configure and obtain Object Meta:

#include "oss_api.h"
#include "aos_http_io.h"
const char *endpoint = "<yourEndpoint>";
const char *access_key_id = "<yourAccessKeyId>";
const char *access_key_secret = "<yourAccessKeySecret>";
const char *bucket_name = "<yourBucketName>";
const char *object_name = "<yourObjectName>";
void init_options(oss_request_options_t *options)
    options->config = oss_config_create(options->pool);
    /* Use a char* string to initialize aos_string_t. */
    aos_str_set(&options->config->endpoint, endpoint);
    aos_str_set(&options->config->access_key_id, access_key_id);
    aos_str_set(&options->config->access_key_secret, access_key_secret);
    /* Determine whether the CNAME is used. The value 0 indicates that the CNAME is not used. */
    options->config->is_cname = 0;
    /* Configure network parameters, such as timeout. */
    options->ctl = aos_http_controller_create(options->pool, 0);
int main(int argc, char *argv[])
    /* Call the aos_http_io_initialize method in main() to initialize global resources, such as networks and memories. */
    if (aos_http_io_initialize(NULL, 0) ! = AOSE_OK) {
    /* Memory pool used to manage memories, equivalent to apr_pool_t. The implementation code is included in the apr library. */
    aos_pool_t *pool;
    /* Re-create a memory pool. The second parameter is NULL, indicating that the new pool does not inherit any other memory pool. */
    aos_pool_create(&pool, NULL);
    /* Create and initialize options. This parameter includes global configuration information, such as endpoint, access_key_id, acces_key_secret, is_cname, and curl. */
    oss_request_options_t *oss_client_options;
    /* Allocate the memories in the memory pool to options. */
    oss_client_options = oss_request_options_create(pool);
    /* Initialize oss_client_options. */
    /* Initialize parameters. */
    aos_string_t bucket;
    aos_string_t object;
    aos_table_t *headers;
    aos_list_t buffer;
    aos_table_t *resp_headers = NULL; 
    aos_status_t *resp_status = NULL; 
    aos_buf_t *content = NULL;
    char *content_length_str = NULL;
    char *object_type = NULL;
    char *object_author = NULL;
    int64_t content_length = 0;
    aos_str_set(&bucket, bucket_name);
    aos_str_set(&object, object_name);
    headers = aos_table_make(pool, 2);
    // Configure custom Object Meta. */
    apr_table_set(headers, "Expires", "Fri, 28 Feb 2032 05:38:42 GMT"); 
    apr_table_set(headers, "x-oss-meta-author", "oss");
    content = aos_buf_pack(oss_client_options->pool, object_content, strlen(object_content));
    aos_list_add_tail(&content->node, &buffer);
    /* Set object permissions and upload the object from the cache. */
    resp_status = oss_put_object_from_buffer(oss_client_options, &bucket, &object, 
               &buffer, headers, &resp_headers);
    if (aos_status_is_ok(resp_status)) {
        printf("put object from buffer with md5 succeeded\n");
    } else {
        printf("put object from buffer with md5 failed\n");
    /* Obtain the object permission. */
    resp_status = oss_get_object_meta(oss_client_options, &bucket, &object, &resp_headers);
    if (aos_status_is_ok(resp_status)) {
        content_length_str = (char*)apr_table_get(resp_headers, OSS_CONTENT_LENGTH);
        if (content_length_str ! = NULL) {
            content_length = atol(content_length_str);
        object_author = (char*)apr_table_get(resp_headers, OSS_AUTHORIZATION);
        object_type = (char*)apr_table_get(resp_headers, OSS_OBJECT_TYPE);
        printf("get object meta succeeded, object author:%s, object type:%s, content_length:%ld\n", object_author, object_type, content_length);
    } else {
        printf("req:%s, get object meta failed\n", resp_status->req_id);
    /* Release the memory pool, that is, the memories allocated to resources during the request. */
    /* Release the allocated global resources. */
    return 0;
Note For detailed information about HTTP header, see RFC2616.