^HW - Host Directory List

^HW lists the contents of one of the printer's memory devices, and returns the listing over the link as fixed-width ASCII. Software that downloads fonts and graphics uses it to check whether an object is already resident. Its printed counterpart is ^WD, and the difference decides this page: ^HW answers the host and renders no label.

Syntax

^HWd:o.x,f

Support

Recognised, deliberately skippedparsed: none · state: none · rendered: none

Accepted and skipped, because it configures the printer rather than the label. It cannot change the rendered output, and Labelary skips it too.

Returns a file listing over the printer's link. The store it would list holds only the objects ~DG downloaded earlier in the same request. The end of the request discards it, so a listing would be near-empty. The renderer does not parse this command. It reports IGNORED_COMMAND at info severity, which does not reach X-Warnings. Labelary is also silent, so the rendered label is identical in both engines. — not pinned by a test

Labelary renders this command.

Parameters

dStorage deviceoptional · single character

Which memory device to list: R:, E:, B:, A: or Z:. This service keeps one object store, so the device letter would not narrow the search.

Default: R:
Invalid value: not documented, and we have not measured it. The renderer does not parse or measure this command.
Test coverage

oObject nameoptional · text

Name pattern to match, one to eight alphanumeric characters. * and ? are wildcards, so ^HWR:*.* lists everything.

Default: *
Invalid value: not documented, and we have not measured it. The renderer does not parse or measure this command.
Test coverage

xExtensionoptional · text

Extension pattern to match, * for any.

Default: *
Invalid value: not documented, and we have not measured it. The renderer does not parse or measure this command.
Test coverage

fListing formatoptional · one of a set

Layout of the reply for the host.

Default: D
Invalid value: not documented, and we have not measured it. The renderer does not parse or measure this command.
Test coverage: No documented value is exercised by a test (D, C).

D: Default one-entry-per-line listing (default)
C: Column layout

Behavior

The reply has a fixed shape, not free text:

<STX>;
a DIR R: header line;
one line per object that starts with * — eight columns for the name, a full stop and three for the extension, then the size and three reserved option flags;
a -xxxxxxx bytes free line;
<ETX>.

The columns are fixed, so a name longer than eight characters cannot appear in full.

Like every ^ command, the printer processes ^HW in the order it appears in the format, not on arrival. The guide adds that the printer answers when it can, not immediately.

A render request has no link to answer on, and little to list. Its object store holds only what its own ~DG or ~DY commands put there, and it ends with the request. The renderer ignores the command, and the page is unchanged. It reports IGNORED_COMMAND at info severity, which does not reach X-Warnings. Labelary is also silent.

Differences from the specification

Labelary against the ZPL II guide

Where Labelary — our compatibility target — behaves differently from the printed specification.

The listing-format argument f is Labelary's, not the guide's. The 2006 guide's format line is ^HWd:o.x and its parameter table documents three arguments, with no choice of reply layout. — not pinned by a test

Example

Listing everything on R: in the default reply layout. The earlier version of this page showed ^HWR: with no name or extension pattern; the guide's own example is ^HWR:*.*, which is what is used here.

^XA
^HWR:*.*,D
^FO50,50^A0N,40,40^FDDirectory query^FS
^XZ

Open in viewer

^WD Print Directory LabelPrints a label listing the objects held in printer memory.
^HY Upload GraphicsSends a stored graphic back to the host as an image file.
^ID Image DeleteDeletes a stored object from printer memory.
~DG Download GraphicDownloads an ASCII-hex bitmap into printer memory as a `.GRF` object.
^HZ Display Description InformationSends printer status, configuration or object descriptions back to the host as XML.