FileSystem is an abstract file system API,
LocalFileSystem is an implementation accessing files
on the local machine. SubTreeFileSystem is an implementation that delegates
to another implementation after prepending a fixed base path
LocalFileSystem$create() returns the object and takes no arguments.
SubTreeFileSystem$create() takes the following arguments:
base_path, a string path
base_fs, a FileSystem object
S3FileSystem$create() optionally takes arguments:
anonymous: logical, default FALSE. If true, will not attempt to look up
credentials using standard AWS configuration methods.
access_key, secret_key: authentication credentials. If one is provided,
the other must be as well. If both are provided, they will override any
AWS configuration set at the environment level.
session_token: optional string for authentication along with
access_key and secret_key
role_arn: string AWS ARN of an AccessRole. If provided instead of access_key and
secret_key, temporary credentials will be fetched by assuming this role.
session_name: optional string identifier for the assumed role session.
external_id: optional unique string identifier that might be required
when you assume a role in another account.
load_frequency: integer, frequency (in seconds) with which temporary
credentials from an assumed role session will be refreshed. Default is
900 (i.e. 15 minutes)
region: AWS region to connect to. If omitted, the AWS library will
provide a sensible default based on client configuration, falling back
to "us-east-1" if no other alternatives are found.
endpoint_override: If non-empty, override region with a connect string
such as "localhost:9000". This is useful for connecting to file systems
that emulate S3.
scheme: S3 connection transport (default "https")
background_writes: logical, whether OutputStream writes will be issued
in the background, without blocking (default TRUE)
allow_bucket_creation: logical, if TRUE, the filesystem will create
buckets if $CreateDir() is called on the bucket level (default FALSE).
allow_bucket_deletion: logical, if TRUE, the filesystem will delete
buckets if$DeleteDir() is called on the bucket level (default FALSE).
GcsFileSystem$create() optionally takes arguments:
anonymous: logical, default FALSE. If true, will not attempt to look up
credentials using standard GCS configuration methods.
access_token: optional string for authentication. Should be provided along
with expiration
expiration: optional date representing point at which access_token will
expire.
json_credentials: optional string for authentication. Point to a JSON
credentials file downloaded from GCS.
endpoint_override: if non-empty, will connect to provided host name / port,
such as "localhost:9001", instead of default GCS ones. This is primarily useful
for testing purposes.
scheme: connection transport (default "https")
default_bucket_location: the default location (or "region") to create new
buckets in.
retry_limit_seconds: the maximum amount of time to spend retrying if
the filesystem encounters errors. Default is 15 seconds.
default_metadata: default metadata to write in new objects.
$GetFileInfo(x): x may be a FileSelector or a character
vector of paths. Returns a list of FileInfo
$CreateDir(path, recursive = TRUE): Create a directory and subdirectories.
$DeleteDir(path): Delete a directory and its contents, recursively.
$DeleteDirContents(path): Delete a directory's contents, recursively.
Like $DeleteDir(),
but doesn't delete the directory itself. Passing an empty path ("") will
wipe the entire filesystem tree.
$DeleteFile(path) : Delete a file.
$DeleteFiles(paths) : Delete many files. The default implementation
issues individual delete operations in sequence.
$Move(src, dest): Move / rename a file or directory. If the destination
exists:
if it is a non-empty directory, an error is returned
otherwise, if it has the same type as the source, it is replaced
otherwise, behavior is unspecified (implementation-dependent).
$CopyFile(src, dest): Copy a file. If the destination exists and is a
directory, an error is returned. Otherwise, it is replaced.
$OpenInputStream(path): Open an input stream for
sequential reading.
$OpenInputFile(path): Open an input file for random
access reading.
$OpenOutputStream(path): Open an output stream for
sequential writing.
$OpenAppendStream(path): Open an output stream for
appending.
$type_name: string filesystem type name, such as "local", "s3", etc.
$region: string AWS region, for S3FileSystem and SubTreeFileSystem
containing a S3FileSystem
$base_fs: for SubTreeFileSystem, the FileSystem it contains
$base_path: for SubTreeFileSystem, the path in $base_fs which is considered
root in this SubTreeFileSystem.
On S3FileSystem, $CreateDir() on a top-level directory creates a new bucket.
When S3FileSystem creates new buckets (assuming allow_bucket_creation is TRUE),
it does not pass any non-default settings. In AWS S3, the bucket and all
objects will be not publicly visible, and will have no bucket policies
and no resource tags. To have more control over how buckets are created,
use a different API to create them.