How to check whether a file exists - Object Storage Service

This topic describes how to check whether a file exists.

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, access credentials are obtained from environment variables. For more information about how to configure access credentials, see Configure access credentials.
In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient instance by using custom domain names or Security Token Service (STS), see Configure OSSClient instances.
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 sample code shows how to check whether a file exists.

package main

import (
	"log"

	"github.com/aliyun/aliyun-oss-go-sdk/oss"
)

func main() {
	// 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 set.
	provider, err := oss.NewEnvironmentVariableCredentialsProvider()
	if err != nil {
		log.Fatalf("Failed to create credentials provider: %v", err)
	}

	// Create an OSSClient instance.
	// Set yourEndpoint to the Endpoint of the bucket. For example, for a bucket in the China (Hangzhou) region, set the value to https://oss-cn-hangzhou.aliyuncs.com. For other regions, set the value as needed.
	// Set yourRegion to the region where the bucket is located. For example, for a bucket in the China (Hangzhou) region, set the value to cn-hangzhou. For other regions, set the value as needed.
	clientOptions := []oss.ClientOption{oss.SetCredentialsProvider(&provider)}
	clientOptions = append(clientOptions, oss.Region("yourRegion"))
	// Set the signature version.
	clientOptions = append(clientOptions, oss.AuthVersion(oss.AuthV4))
	client, err := oss.New("yourEndpoint", "", "", clientOptions...)
	if err != nil {
		log.Fatalf("Failed to create OSS client: %v", err)
	}

	// Set yourBucketName to the name of the bucket.
	bucketName := "yourBucketName" // Replace with the actual bucket name.
	bucket, err := client.Bucket(bucketName)
	if err != nil {
		log.Fatalf("Failed to get bucket: %v", err)
	}

	// Check whether the file exists.
	// Set yourObjectName to the full path of the object. Do not include the bucket name.
	objectName := "yourObjectName" // Replace with the actual object path.
	isExist, err := bucket.IsObjectExist(objectName)
	if err != nil {
		log.Fatalf("Failed to check if object exists: %v", err)
	}
	log.Printf("Exist: %t\n", isExist)
}

References

For more information about the API operation for checking whether a file exists, see IsObjectExist.