'Determine if an object exists in a S3 bucket based on wildcard

Can someone please show me how to determine if a certain file/object exists in a S3 bucket and display a message if it exists or if it does not exist.

Basically I want it to:

1) Check a bucket on my S3 account such as testbucket

2) Inside of that bucket, look to see if there is a file with the prefix test_ (test_file.txt or test_data.txt).

3) If that file exists, then display a MessageBox (or Console message) that the file exists, or that the file does not exist.

Can someone please show me how to do this?

c++sharp

Solution 1:^[1]

Using the AWSSDK For .Net I Currently do something along the lines of:

public bool Exists(string fileKey, string bucketName)
{
        try
        {
            response = _s3Client.GetObjectMetadata(new GetObjectMetadataRequest()
               .WithBucketName(bucketName)
               .WithKey(key));

            return true;
        }

        catch (Amazon.S3.AmazonS3Exception ex)
        {
            if (ex.StatusCode == System.Net.HttpStatusCode.NotFound)
                return false;

            //status wasn't not found, so throw the exception
            throw;
        }
}

It kinda sucks, but it works for now.

Solution 2:^[2]

Use the S3FileInfo.Exists method:

using (var client = Amazon.AWSClientFactory.CreateAmazonS3Client(accessKey, secretKey))
{
    S3FileInfo s3FileInfo = new Amazon.S3.IO.S3FileInfo(client, "your-bucket-name", "your-file-name");
    if (s3FileInfo.Exists)
    {
         // file exists
    }
    else
    {
        // file does not exist
    }   
}

Solution 3:^[3]

This solves it:

List the bucket for existing objects and use a prefix like so.

    var request = new ListObjectsRequest()
        .WithBucketName(_bucketName)
        .WithPrefix(keyPrefix);

    var response = _amazonS3Client.ListObjects(request);

    var exists = response.S3Objects.Count > 0;

    foreach (var obj in response.S3Objects) {
        // act
    }

Solution 4:^[4]

I know this question is a few years old but the new SDK handles this beautifully. If anyone is still searching this. You are looking for S3DirectoryInfo Class

using (IAmazonS3 s3Client = new AmazonS3Client(accessKey, secretKey))
{
    S3DirectoryInfo s3DirectoryInfo = new Amazon.S3.IO.S3DirectoryInfo(s3Client, "testbucket");
    if (s3DirectoryInfo.GetFiles("test*").Any())
    {
        //file exists -- do something
    }
    else
    {
        //file doesn't exist -- do something else
    }
}

Solution 5:^[5]

Not sure if this applies to .NET Framework, but the .NET Core version of AWS SDK (v3) only supports async requests, so I had to use a slightly different solution:

/// <summary>
/// Determines whether a file exists within the specified bucket
/// </summary>
/// <param name="bucket">The name of the bucket to search</param>
/// <param name="filePrefix">Match files that begin with this prefix</param>
/// <returns>True if the file exists</returns>
public async Task<bool> FileExists(string bucket, string filePrefix)
{
    // Set this to your S3 region (of course)
    var region = Amazon.RegionEndpoint.USEast1;

    using (var client = new AmazonS3Client(region))
    {
        var request = new ListObjectsRequest {
            BucketName = bucket,
            Prefix = filePrefix,
            MaxKeys = 1
        };

        var response = await client.ListObjectsAsync(request, CancellationToken.None);

        return response.S3Objects.Any();
    }
}

And, if you want to search a folder:

/// <summary>
/// Determines whether a file exists within the specified folder
/// </summary>
/// <param name="bucket">The name of the bucket to search</param>
/// <param name="folder">The name of the folder to search</param>
/// <param name="filePrefix">Match files that begin with this prefix</param>
/// <returns>True if the file exists</returns>
public async Task<bool> FileExists(string bucket, string folder, string filePrefix)
{
    return await FileExists(bucket, $"{folder}/{filePrefix}");
}

Usage:

var testExists = await FileExists("testBucket", "test_");
// or...
var testExistsInFolder = await FileExists("testBucket", "testFolder/testSubFolder", "test_");

Solution 6:^[6]

I know this question is a few years old but the new SDK nowdays handles this in an easier manner.

  public async Task<bool> ObjectExistsAsync(string prefix)
  {
     var response = await _amazonS3.GetAllObjectKeysAsync(_awsS3Configuration.BucketName, prefix, null);
     return response.Count > 0;
  }

Where _amazonS3 is your IAmazonS3 instance and _awsS3Configuration.BucketName is your bucket name.

You can use your complete key as a prefix.

Solution 7:^[7]

I used the following code in C# with Amazon S3 version 3.1.5(.net 3.5) to check if the bucket exists:

BasicAWSCredentials credentials = new BasicAWSCredentials("accessKey", "secretKey");

AmazonS3Config configurationAmazon = new AmazonS3Config();
configurationAmazon.RegionEndpoint = S3Region.EU; // or you can use ServiceUrl

AmazonS3Client s3Client = new AmazonS3Client(credentials, configurationAmazon);


S3DirectoryInfo directoryInfo = new S3DirectoryInfo(s3Client, bucketName);
            bucketExists = directoryInfo.Exists;// true if the bucket exists in other case false.

I used the followings code(in C# with Amazon S3 version 3.1.5 .net 3.5) the file Exists.

Option 1:

S3FileInfo info = new S3FileInfo(s3Client, "butcketName", "key");
bool fileExists = info.Exists; // true if the key Exists in other case false

Option 2:

ListObjectsRequest request = new ListObjectsRequest();
        try
        {
            request.BucketName = "bucketName";
            request.Prefix = "prefix"; // or part of the key
            request.MaxKeys = 1; // max limit to find objects
            ListObjectsResponse response = s3Client .ListObjects(request);
            return response.S3Objects.Count > 0;
        }

Solution 8:^[8]

I'm not familiar with C#, but I use this method from Java (conversion to c# is immediate):

public boolean exists(AmazonS3 s3, String bucket, String key) {
    ObjectListing list = s3.listObjects(bucket, key);
    return list.getObjectSummaries().size() > 0;
}

Solution 9:^[9]

 s3 = new S3(S3KEY, S3SECRET, false);
 res = s3->getObjectInfo(bucketName, filename);

It will return array if file exists

Solution 10:^[10]

try this one:

    NameValueCollection appConfig = ConfigurationManager.AppSettings;

        AmazonS3 s3Client = AWSClientFactory.CreateAmazonS3Client(
                appConfig["AWSAccessKey"],
                appConfig["AWSSecretKey"],
                Amazon.RegionEndpoint.USEast1
                );

S3DirectoryInfo source = new S3DirectoryInfo(s3Client, "BUCKET_NAME", "Key");
if(source.Exist)
{
   //do ur stuff
}

Solution 11:^[11]

using Amazon;
using Amazon.S3;
using Amazon.S3.IO;
using Amazon.S3.Model;

string accessKey = "xxxxx";
string secretKey = "xxxxx";
string regionEndpoint = "EU-WEST-1";
string bucketName = "Bucket1";
string filePath = "https://Bucket1/users/delivery/file.json"

public bool FileExistsOnS3(string filePath)
{
   try
   {
      Uri myUri = new Uri(filePath);
      string absolutePath = myUri.AbsolutePath; // /users/delivery/file.json
      string key = absolutePath.Substring(1); // users/delivery/file.json
      using(var client = AWSClientFactory.CreateAmazonS3Client(accessKey, secretKey, regionEndpoint))
      {
         S3FileInfo file = new S3FileInfo(client, bucketName, key);
         if (file.Exists)
         {
            return true;
            // custom logic
         }
         else
         {
            return false;
            // custom logic
         }
      }
   }
   catch(AmazonS3Exception ex)
   {
      return false;
   }
}

Solution 12:^[12]

There is an overload for GetFileSystemInfos Notice this line has filename.*

var files= s3DirectoryInfo.GetFileSystemInfos("filename.*");

public bool Check()
{
    var awsCredentials = new Amazon.Runtime.BasicAWSCredentials("AccessKey", "SecretKey");

      using (var client = new AmazonS3Client(awsCredentials, Amazon.RegionEndpoint.USEast1))
       {
       S3DirectoryInfo s3DirectoryInfo = new S3DirectoryInfo(client, bucketName, "YourFilePath");
                var files= s3DirectoryInfo.GetFileSystemInfos("filename.*");
                if(files.Any())
                {
                    //fles exists
                }
            }
        }

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Paul Suart
Solution 2	Mitch Wheat
Solution 3	Alvis
Solution 4	Mitch Wheat
Solution 5	2Toad
Solution 6	Razvan Dumitru
Solution 7	user5219763
Solution 8	Monkiki
Solution 9	Deepika Patel
Solution 10	Prasad Shigwan
Solution 11	Tahir77667
Solution 12

'Determine if an object exists in a S3 bucket based on wildcard

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