FRONTEND-SPEC(7)

💖 NAME 💖

okay so this is frontend-spec, bestie — it's the manpage (section 7, we fancy) that explains the literal interface between jw and its frontends. like, the whole glue that makes them talk to each other 🫶

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✨ DESCRIPTION ✨

so here's the tea: jw(1) calls frontends like frontends/docbook to get the info that's specific to a given input format. the frontend knows which info to hand back by peeking at the first command line parameter 👀 and it gets all the data it needs via environment variables that are already set up and ready to use. no cap, they're just sitting there waiting for you.

this doc describes that command line parameter and those environment variables. that's it, that's the vibe.

and the exit code situation is simple: the frontend should return 0 if there weren't any problem, and return a positive value otherwise. that's the whole rule. slay 💅

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🌸 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). ⭐

quick vibe check: those "valid only while determining…" notes are fr fr important — each variable is only in play during that specific step, don't go assuming it's set the whole time 🙈

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🎀 FILES 🎀

literally nothing listed here, bestie — the section is just vibes and empty space 💀

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🦋 SEE ALSO 🦋

• backend-spec(7) — the sibling page, go read it, iykyk 💜

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👑 AUTHORS 👑

• Jochem Huhmann <joh@revier.com> — the icon who wrote this, show some respect 🌈

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that's the whole page, bestie!! this was FRONTEND-SPEC(7), dated 05 December 2025, and honestly it ate 💅✨ go forth and write frontends that return 0, mwah 🍓