`bm head`

Syntax

The bm head command displays the first n lines of an object, where n is an argument specified to the command.

bm head does not perform any transformation or formatting of object contents to facilitate readability. You can also use bm head against the local filesystem to produce similar results to the head commandline tool.

EXAMPLE

The following command returns the first 10 lines of an object in the mydata bucket on the mybuckit Buckit deployment:

bm head mybuckit/mydata/myobject.txt

SYNTAX

The command has the following syntax:

bm [GLOBALFLAGS] head                     \
                 [--lines int]            \
                 [--rewind "string"]      \
                 [--version-id "string"]  \
                 [--enc-c "string"]       \
                 ALIAS [ALIAS ...]

Brackets [] indicate optional parameters.
Parameters sharing a line are mutually dependent.
Parameters separated using the pipe | operator are mutually exclusive.

Copy the example to a text editor and modify as-needed before running the command in the terminal/shell.

Parameters

ALIAS

Required

The object or objects to print.

For an object on Buckit, specify the alias and the full path to that object (e.g. bucket and path to object). For example:

bm head play/mybucket/object.txt

You can specify multiple objects on the same or different Buckit deployments. For example:

bm head ~/mydata/object.txt mybuckit/mydata/object.txt

For an object on a local filesystem, specify the full path to that object. For example:

bm head ~/mydata/object.txt

--lines, n

Optional

The number of lines to print.

Defaults to 10.

--enc-c

Optional

Encrypt or decrypt objects using server-side SSE-C encryption with client-managed keys.

The parameter accepts a key-value pair formatted as KEY=VALUE

`KEY`	The full path to the object as `alias/bucket/path/object.ext`. You can specify only the top-level path to use a single encryption key for all operations in that path.
`VALUE`	Specify either a 32-byte RawBase64-encoded key or a 64-byte hex-encoded key for use with SSE-C encryption. Raw Base64 encoding rejects `=`-padded keys. Omit the padding or use a Base64 encoder that supports RAW formatting.

KEY

The full path to the object as alias/bucket/path/object.ext.

You can specify only the top-level path to use a single encryption key for all operations in that path.

VALUE

Specify either a 32-byte RawBase64-encoded key or a 64-byte hex-encoded key for use with SSE-C encryption.

Raw Base64 encoding rejects =-padded keys. Omit the padding or use a Base64 encoder that supports RAW formatting.

KEY - the full path to the object as alias/bucket/path/object.
VALUE - the 32-byte RAW Base64-encoded data key to use for encrypting object(s).

For example:

# RawBase64-Encoded string "mybucket32byteencryptionkeyssec"
--enc-c "mybuckit/mybucket/prefix/object.obj=bXlidWNrZXQzMmJ5dGVlbmNyeXB0aW9ua2V5c3NlYwo"

You can specify multiple encryption keys by repeating the parameter.

Specify the path to a prefix to apply encryption to all matching objects at that path:

--enc-c "mybuckit/mybucket/prefix/=bXlidWNrZXQzMmJ5dGVlbmNyeXB0aW9ua2V5c3NlYwo"

Note

Buckit strongly recommends against using SSE-C encryption in production workloads. Use SSE-KMS via the --enc-kms or SSE-S3 via --enc-s3 parameters instead.

--rewind

Optional

Directs bm head to operate only on the object version(s) that existed at specified point-in-time.

To rewind to a specific date in the past, specify the date as an ISO8601-formatted timestamp. For example: --rewind "2020.03.24T10:00".
To rewind a duration in time, specify the duration as a string in #d#hh#mm#ss format. For example: --rewind "1d2hh3mm4ss".

--rewind requires that the specified ALIAS be an S3-compatible service that supports Bucket Versioning. For Buckit deployments, use bm version to enable or disable bucket versioning.

--version-id, vid

Optional

Directs bm head to operate only on the specified object version.

--version-id requires that the specified ALIAS be an S3-compatible service that supports Bucket Versioning. For Buckit deployments, use bm version to enable or disable bucket versioning.

Global Flags

This command supports any of the global flags.

Examples

View Partial Contents of an Object

Use bm head to return the first 10 lines of an object:

bm head ALIAS/PATH

Replace ALIAS with the alias of the S3-compatible host.
Replace PATH with the path to the object on the S3-compatible host.

View Partial Contents of an Object at a Point in Time

Use bm head --rewind to return the first 10 lines of the object at a specific point-in-time in the past:

bm head ALIAS/PATH --rewind DURATION

Replace ALIAS with the alias of the S3-compatible host.
Replace PATH with the path to the object on the S3-compatible host.
Replace DURATION with the point-in-time in the past at which the command returns the object. For example, specify 30d to return the version of the object 30 days prior to the current date.

Requires Versioning

bm head requires bucket versioning to use this feature. Use bm version to enable versioning on a bucket.

View Partial Contents of an Object with Specific Version

Use bm head --version-id to return the first 10 lines of the object at a specific point-in-time in the past:

bm head ALIAS/PATH --version-id VERSION

Replace ALIAS with the alias of the S3-compatible host.
Replace PATH with the path to the object on the S3-compatible host.
Replace VERSION with the version of the object. For example, specify 30d to return the version of the object 30 days prior to the current date.

Requires Versioning

bm head requires bucket versioning to use this feature. Use bm version to enable versioning on a bucket.

Behavior

S3 Compatibility

The bm commandline tool is built for compatibility with the AWS S3 API and is tested with Buckit and AWS S3 for expected functionality and behavior.

Buckit provides no guarantees for other S3-compatible services, as their S3 API implementation is unknown and therefore unsupported. While bm commands may work as documented, any such usage is at your own risk.