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?
Solution 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:
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:
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:
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:
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_");