Object Storage Service:Check whether a file exists (C++ SDK)

Usage notes

• In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS from other Alibaba Cloud services in the same region as OSS, use an internal endpoint. For more information about OSS regions and endpoints, see Regions and endpoints.

• In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient by using custom domain names or Security Token Service (STS), see Create an OSSClient instance.

• To determine whether an object exists, you must have the oss:GetObject permission. For more information, see Attach a custom policy to a RAM user.

Sample code

The following code shows how to check whether a file exists:

#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;

int main(void)
{
    /* Initialize OSS account information. */
            
    /* Set yourEndpoint to the endpoint of the region where the bucket is located. For example, for the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
    std::string Endpoint = "yourEndpoint";
    /* Set yourRegion to the region where the bucket is located. For example, for the China (Hangzhou) region, set the region to cn-hangzhou. */
    std::string Region = "yourRegion";
    /* Specify the bucket name. Example: examplebucket. */
    std::string BucketName = "examplebucket";
    /* Specify the full path of the object. The full path cannot include the bucket name. Example: exampledir/exampleobject.txt. */
    std::string ObjectName = "exampledir/exampleobject.txt";
    /* Initialize network resources. */
    InitializeSdk();

    ClientConfiguration conf;
    conf.signatureVersion = SignatureVersionType::V4;
    /* Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. */
    auto credentialsProvider = std::make_shared<EnvironmentVariableCredentialsProvider>();
    OssClient client(Endpoint, credentialsProvider, conf);
    client.SetRegion(Region);

    /* Check whether the file exists. */
    auto outcome = client.DoesObjectExist(BucketName, ObjectName);

    if (outcome) {
      std::cout << "The Object exists!" << std::endl;                       
    }                              
    else {                         
      std::cout << "The Object does not exist!" << std::endl;
    }

    /* Release network resources. */
    ShutdownSdk();
    return 0;
}

References

For the complete sample code for this operation, see GitHub.