Is there a way to touch() a file in Amazon S3?

Question

I'm currently working with Amazon S3 and I am writing a program that uses the modified dates. I'm looking for a way to edit the modified dates.

I could loop trough all the files and save them as they are, but this sounds like a bad solution.

In PHP there is this function touch().

Does anyone know a solution, or has the same problem?

Answer 1

In response to @Daniel Golden's comment on @tkotisis answer. It looks like at least the AWS CLI tools do not let you copy an item on to itself. You can however 'force' a copy by updating the metadata.

$ aws s3 cp --metadata '{"touched":"now"}' s3://path/to/object s3://path/to/object

This recreates the object (downloads to the caller and reuploads it) replacing its content, owner and metadata. This will also trigger any attached Lambda events.

Answer 2

You can achieve the same through a copy object request, specifying the CopySource to be same as the target key.

In essence, this will issue a PUT Object - COPY request to S3 with the corresponding source and target bucket/key.

Answer 3

Here is another whay to upload a null (or o Byte) file to S3. I verified this works You can also use the S3 API to upload a file with no body, like so:

aws s3api put-object --bucket "myBucketName" --key "dir-1/my_null_file"

Normally you would specify a --body blob, but its option and will just add the key as expected. See more on S3 API put-object

The version of AWS CLI tested with is: aws-cli/2.0.4 Python/3.7.5 Windows/10 botocore/2.0.0dev8

Here's how I did it in PHP (even works in outdated 5.4, had to go way back):

// Init an S3Client
$awsConfig = $app->config('aws');
$aws       = Aws::factory($awsConfig);
$s3Bucket  = $app->config('S3_Bucket');
$s3Client  = $aws->get('s3');

// Set null/empty file.
$result = $s3Client->putObject([
    'Bucket' => $s3Bucket,
    'Key' => "dir-1/my_null_file",
    'Body' => '',
    'ServerSideEncryption' => 'AES256',
]);

Answer 4

I find myself performing the copy trick pretty often when testing, to the extent that I've added a handy function to my .bashrc:

s3-touch() {
  aws s3 cp \
    --metadata 'touched=touched' \
    --recursive --exclude="*" \
    --include="$2" \
    "${@:3}" \
    "$1" "$1"
}

Example usage:

# will do a dryrun on a copy operation
s3-touch s3://bucket/prefix/ "20200311*" --dryrun

# the real thing, creating events for all objects
# in s3://bucket/prefix/ that start with 20200311
s3-touch s3://bucket/prefix/ "20200311*"

I'm doing this mainly for the S3-events that I want to trigger.

Answer 5

Following @g-io answer that simplified my day, here is another version of the same that makes it easy to touch a single file

s3-touch-single() {
  aws s3 cp \
    --metadata 'touched=touched' \
    "${@:3}" \
    "$1" "$1"
}

for example, looping an array of files we need to touch:

paths=("mydir/image.png" "mydir2/image2.png")
for i in "${paths[@]}"; do s3-touch-single "s3://my-bucket/$i"; done

Answer 6

check out https://github.com/emdgroup/awscli-s3touch

It's a plugin to the AWS CLI that adds a touch command.

Usage:

aws s3 touch my-bucket --prefix myfolder/

It works by reading the events attached to the bucket and simulating them client side.