mc head

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

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

mc head myminio/mydata/myobject.txt

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

Required

The object or objects to print.

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

mc head play/mybucket/object.txt

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

mc head ~/mydata/object.txt myminio/mydata/object.txt

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

mc head ~/mydata/object.txt

Optional

The number of lines to print.

Defaults to 10.

Optional

Decrypt the object using server-side SSE-C encryption with client-managed keys. This assumes the object was originally encrypted with SSE-C.

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.

For example:

# RawBase64-Encoded string "mybucket32byteencryptionkeyssec"
--enc-c "myminio/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 "myminio/mybucket/prefix/=bXlidWNrZXQzMmJ5dGVlbmNyeXB0aW9ua2V5c3NlYwo"

Optional

Directs mc 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#ssformat. For example: --rewind "1d2hh3mm4ss".

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

Alias: --vid

Optional

Directs mc 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 AIStor deployments, use mc version to enable or disable bucket versioning.

This command supports any of the global flags.

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

mc 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.

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

mc 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 theobject. For example, specify 30d to return the version of the object 30 days prior to the current date.

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

mc 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.

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

AIStor provides no guarantees for other S3-compatible services, As their S3 API implementation is unknown and therefore unsupported.

While mc commands may work as documented, any such usage is at your own risk.