Checking the existence of an object or folder

You use the HTTP HEAD method to check the existence of an object or folder in a bucket. To check the existence of an object, you need read permission for the bucket containing the object or for the object itself. To check the existence of a folder, you need read permission for the bucket.

In response to a request to check the existence of an object or folder, HCP returns a 200 (OK) status code if the object or folder exists and a 404 (Not Found) status code if the object or folder does not exist. If you do not have read permission for the bucket or object, HCP returns a 403 (Forbidden) status code.

Request line

Depending on whether the bucket name is included in the hostname in the S3 compatible request, a request to check the existence of an object, object version, or folder has either of these formats:

• With the bucket name included in the hostname:

  HEAD /(object-name[?versionId=version-id])|(folder-name(/|%2F)) HTTP/1.1

• With the bucket name following the hostname:

  HEAD /bucket-name/(object-name[?versionId=version-id])|(folder-name(/|%2F)) HTTP/1.1

Required headers

The next list describes the required headers to use in a request to check the existence of an object, object version, or folder.

Authorization

Specifies user credentials or requests anonymous access.

Date

Specifies the date and time when the request is being made according to the requester. Normally, this is the current date and time.

The date and time must always be specified using Greenwich Mean Time (GMT).

To specify the date and time, use this format:

DDD, dd MMM yyyy HH:mm:ss (+0000|GMT)

In this format:

DDD

The three-letter abbreviation for the day of the week, with an uppercase first letter (for example, Mon).

dd

The two-digit day of the month.

MMM

The three-letter abbreviation for the month, with an uppercase first letter (for example, Feb).

yyyy

The four-digit year.

HH

The hour on a 24-hour clock.

mm

The number of minutes.

ss

The number of seconds.

For example:

Thu, 23 Mar 2017 14:27:05 +0000

All S3 compatible requests must include either a Date header or an x-amz-date header. If a request includes both headers, HCP uses the date and time in the x-amz-date header.

Host

Specifies the hostname for the request. The host name identifies either a tenant or a bucket.

For a tenant, use this format:

tenant-name.hcp-domain-name

For a bucket, use this format:

bucket-name.tenant-name.hcp-domain-name

x-amz-date

Specifies the date and time at which the request is being made according to the requester. Normally, this is the current date and time.

For the valid values for this header, see the description of the Date header above.

Optional headers

If-Match

Specifies one or more values for comparison with the ETag of the specified item. If the ETag matches one of the specified values, HCP continues processing the request. If the ETag does not match any of the specified values, HCP returns a 412 (Precondition Failed) status code.

To specify the values for this header, use this format:

"value"[, "value"]...

In this format, each value can be any string of one or more characters and must be enclosed in double quotation marks (").

Alternatively, you can specify a single asterisk (*) as the value for the If-Match header. All ETags match an asterisk in an If-Match header.

If-Modified-Since

Specifies a date and time, in Greenwich Mean Time (GMT), for comparison with the date and time the specified item was last modified. If the modification date and time is later than the specified date and time, HCP continues processing the request. If the modification date and time is equal to or earlier than the specified date and time, HCP returns a 304 (Not Modified) status code.

To specify the date and time for this header, use one of these formats:

• DDD, dd MMM yyyy HH:mm:ss (+0000|GMT)

  For example: Tue, 07 Feb 2017 14:27:05 +0000

• DDDD, dd-MMM-yyyy HH:mm:ss (+0000|GMT)

  For example: Tuesday, 07-Feb-17 14:27:05 +0000

• DDD MMM d HH:mm:ss yyyy

  For example: Tue Feb 7 14:27:05 2017

If the value specified by the If-Modified-Since header does not conform to one of the formats shown above, the header is ignored.

If-None-Match

Specifies one or more values for comparison with the ETag of the specified item. If the ETag does not match any of the specified values, HCP continues processing the request. If the ETag matches any of the specified values, HCP returns a 304 (Not Modified) status code.

To specify the values for this header, use this format:

"value"[, "value"]...

In this format, each value can be any string of one or more characters and must be enclosed in double quotation marks (").

Alternatively, you can specify a single asterisk (*) as the value for the If-None-Match header. No ETags match an asterisk in an If-None-Match header.

If-Unmodified-Since

Specifies a date and time, in Greenwich Mean Time (GMT), for comparison with the date and time the specified item was last modified. If the modification date and time is equal to or earlier than the specified date and time, HCP continues processing the request. If the modification date and time is later than the specified date and time, HCP returns a 412 (Precondition Failed) status code.

For valid values, see the description of the If-Modified-Since header above.

Response headers

The next list describes the headers returned in response to a successful request to check the existence an object, object version, or folder.

Accept-Ranges

Indicates that HCP can accept requests for part of the object data, specified as a range of bytes. The value of this header is always bytes.

Content-length

Specifies the size, in bytes, of the object, object version, or folder. For a delete marker the size is 0.

Content-Type

Specifies the Internet media type of the object or object version, or folder. This is one of, in order of precedence:

• The Internet media type specified by the response-content-type request parameter.
• The Internet media type specified in the Content-Type header when the object was stored.
• An Internet media type determined by HCP based on the object name.
• application/octet-stream if HCP cannot determine the Internet media type. For a folder, the value of the Content-Type header is always application/octet-stream.

Date

The date and time when HCP responded to the request, in Greenwich Mean Time (GMT). The date and time are returned in this format:

DDD dd MMM yyyy HH:mm:ss GMT

For example:

Fri, 18 Sep 2020 14:27:05 GMT

ETag

Specifies the ETag for the specified object, object version, or folder. For a delete marker, this is the ETag of the object or object version that was deleted. Unlike objects, delete markers do not have ETags.

Last-Modified

Specifies the date and time when the object, object version, or folder was last modified, in Greenwich Mean Time (GMT).

The date and time are expressed in this format:

DDD, dd MMM yyyy HH:mm:ss GMT

For example:

Tue, 07 Feb 2017 19:46:03 GMT

Modifying an object means modifying its metadata. You cannot modify the content of an object.

x-amz-delete-marker

This header is returned only for delete markers and only if versioning is enabled for the bucket. The value is always true.

x-amz-meta-

For objects and object versions only, specifies a custom metadata property/value pair. The response headers include one x-amz-meta- header for each applicable pair.

x-amz-missing-meta

For objects and object versions only, indicates that the .metapairs annotation for the object or object version does not contain valid XML, that the first line in the annotation does not begin with the metapairs element. This header is returned only when applicable. The value is always 1 (one).

x-amz-version-id

Specifies the version ID of the object. This header is returned only while versioning is enabled for the bucket.

x-amz-object-lock-mode

Specify the Object Lock mode status for an object. The value can be either GOVERNANCE or COMPLIANCE.

GOVERNANCE

Use for objects that are subject to retention policies that are governed by a regulatory body.

COMPLIANCE

Use for objects that are subject to strict regulatory requirements.

Example

x-amz-object-lock-mode: GOVERNANCE

x-amz-object-lock-retain-until-date

Specify the date and time until which an object must be retained. The date and time must be in YYYY-MM-DDTHH:MM:SSZ format, where YYYY represents the year, MM represents the month, DD represents the day, T represents the time separator, HH represents the hour in 24-hour format, MM represents the minute, SS represents the second and Z represents the time zone.

Example

x-amz-object-lock-retain-until-date: 2023-03-30T00:00:00Z

x-amz-object-lock-legal-hold

Specify the Legal hold status of an object version. Valid values are ON and OFF.

ON

You cannot overwrite or delete the object version until you remove the legal hold status.

OFF

You can overwrite or delete the object version.

Example

x-amz-object-lock-legal-hold: ON

x-hcp-labelretentionhold

Specifies whether the object is on labeled hold. A Boolean value of true or false is returned.

For a user without privileged data access permission, the response header returns true or false indicating whether there are one or more labeled holds.

For a user with privileged data access permission:

• If the response header returns true, an additional header, x-hcp-labelretentionhold-labels, is returned.
• If the response header returns false, the x-hcp-labelretentionhold-labels header is not returned

x-hcp-labelretentionhold-labels

If the object is on labeled hold (x-hcp-labelretentionhold:true) and the user has privileged data access and read permissions on the bucket, this header is returned with a JSON format string specifying all labeled holds.

Example

X-HCP-LabelRetentionHold-Labels: [{"id":"UniqueLabelHold-1","hold": true},
[{"id":"UniqueLabelHold-2","hold": true},[{"id":"UniqueLabelHold-3","hold": true}] 

x-hcp-retention

Specifies the retention value for the object being stored. This value can be a fixed date, an offset, a retention class, or a special value.

x-hcp-retentionhold

Specifies whether the object is on hold. A Boolean value of true or false is returned.

Status codes

The following table describes HTTP status codes that can be returned in response to a request to check the existence of an object, object version, or folder.