DocBook Utils
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# frontend-spec

## Name

frontend-spec -- interface between jw and its frontends

## Description

jw(1) calls frontends like `frontends/docbook` to get the informations specific to a given input format. The frontend knows which information to return from the first command line parameter. It gets all necessary data via environment variables ready to use.

This document describes that command line parameter and those environment variables.

The frontend should return 0 if there weren't any problem, and return a positive value otherwise.

## Variables

`$1`

  The command line parameter, specifying which information to return. It can take the following values:

  centralized-catalog

    The frontend must return the DTD-specific centralized catalog name. Centralized catalogs normally reside in `/etc/sgml` and provide the location of all the catalog files useful for handling this input type (the catalog for the DTD, the catalog for the stylesheets, the catalog for the entities, ...)

  style-sheet

    The frontend must return the filename of the style sheet to be used for this document type and with the chosen backend.

`SGML_CATALOGS_DIR`

  The directory where the centralized catalogs reside. It is normally `/etc/sgml`.

  (This variable is valid only while determining the centralized catalog to use.)

`SGML_BASE_DIR`

  The base directory of the SGML system. It is normally `/usr/share/sgml`.

  (This variable is valid only while determining the style sheet to use.)

`SGML_FILE`

  The name of the file to convert.

  (This variable is valid only while determining the centralized catalog to use.)

`SGML_TYPE`

  The type of the backend to use, whether it produces output files to be displayed online or to be printed out. It can take the value `html` or `print`.

  (This variable is valid only while determining the style sheet to use).

`SGML_STYLESHEETS`

  The desired custom stylesheet type, either `none` or `default`. If `none`, the frontend must return the file name of the style sheet provided by the system beneath the docbook-utils. If `default`, the frontend must return the custom stylesheet provided by the docbook-utils.

  (This variable is valid only while determining the style sheet to use).

`SGML_XML`

  The metalanguage of the file to convert, either `sgml` or `xml`.

  (This variable is valid only while determining the centralized catalog to use).

## Files

## See also

backend-spec(7)

## Authors

Jochem Huhmann `<joh@revier.com>`

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