MANDOC(3)

MANDOC(3) | Library Functions Manual | MANDOC(3)

# NAME

`mandoc`, `deroff`, `mparse_alloc`, `mparse_copy`, `mparse_free`, `mparse_open`, `mparse_readfd`, `mparse_reset`, `mparse_result` — mandoc macro compiler library

# SYNOPSIS

`#include <sys/types.h>`
`#include <stdio.h>`
`#include <mandoc.h>`

`#define ASCII_NBRSP`
`#define ASCII_HYPH`
`#define ASCII_BREAK`

struct mparse *
`mparse_alloc`(int options, enum mandoc_os oe_e, char *os_s);

void
`mparse_free`(struct mparse *parse);

void
`mparse_copy`(const struct mparse *parse);

int
`mparse_open`(struct mparse *parse, const char *fname);

void
`mparse_readfd`(struct mparse *parse, int fd, const char *fname);

void
`mparse_reset`(struct mparse *parse);

struct roff_meta *
`mparse_result`(struct mparse *parse);

`#include <roff.h>`

void
`deroff`(char **dest, const struct roff_node *node);

`#include <sys/types.h>`
`#include <mandoc.h>`
`#include <mdoc.h>`

extern const char * const * mdoc_argnames;
extern const char * const * mdoc_macronames;

`#include <sys/types.h>`
`#include <mandoc.h>`
`#include <man.h>`

extern const char * const * man_macronames;

# DESCRIPTION

The `mandoc` library parses a UNIX manual into an abstract syntax tree (AST). UNIX manuals are composed of mdoc(7) or man(7), and may be mixed with roff(7), tbl(7), and eqn(7) invocations.

The following describes a general parse sequence:

1. initiate a parsing sequence with mchars_alloc(3) and `mparse_alloc`();
2. open a file with open(2) or `mparse_open`();
3. parse it with `mparse_readfd`();
4. close it with close(2);
5. retrieve the syntax tree with `mparse_result`();
6. if information about the validity of the input is needed, fetch it with `mparse_updaterc`();
7. iterate over parse nodes with starting from the first member of the returned struct roff_meta;
8. free all allocated memory with `mparse_free`() and mchars_free(3), or invoke `mparse_reset`() and go back to step 2 to parse new files.

# REFERENCE

This section documents the functions, types, and variables available via `<mandoc.h>`, with the exception of those documented in mandoc_escape(3) and mchars_alloc(3).

## Types

enum mandocerr
  An error or warning message during parsing.
enum mandoclevel
  A classification of an enum mandocerr as regards system operation. See the DIAGNOSTICS section in mandoc(1) regarding the meanings of the levels.
struct mparse
  An opaque pointer to a running parse sequence. Created with `mparse_alloc`() and freed with `mparse_free`(). This may be used across parsed input if `mparse_reset`() is called between parses.

## Functions

`deroff`()
  Obtain a text-only representation of a struct roff_node, including text contained in its child nodes. To be used on children of the first member of struct roff_meta. When it is no longer needed, the pointer returned from `deroff`() can be passed to free(3).
`mparse_alloc`()
  Allocate a parser. The arguments have the following effect:
  options
    When the `MPARSE_MDOC` or `MPARSE_MAN` bit is set, only that parser is used. Otherwise, the document type is automatically detected.

    When the `MPARSE_SO` bit is set, roff(7) `so` file inclusion requests are always honoured. Otherwise, if the request is the only content in an input file, only the file name is remembered, to be returned in the sodest field of struct roff_meta.

    When the `MPARSE_QUICK` bit is set, parsing is aborted after the NAME section. This is for example useful in makewhatis(8) `-Q` to quickly build minimal databases.

    When the `MARSE_VALIDATE` bit is set, `mparse_result`() runs the validation functions before returning the syntax tree. This is almost always required, except in certain debugging scenarios, for example to dump unvalidated syntax trees.

  os_e
    Operating system to check base system conventions for. If `MANDOC_OS_OTHER`, the system is automatically detected from `Os`, `-Ios`, or uname(3).
  os_s
    A default string for the mdoc(7) `Os` macro, overriding the `OSNAME` preprocessor definition and the results of uname(3). Passing `NULL` sets no default.

  The same parser may be used for multiple files so long as `mparse_reset`() is called between parses. `mparse_free`() must be called to free the memory allocated by this function. Declared in `<mandoc.h>`, implemented in read.c.

`mparse_free`()
  Free all memory allocated by `mparse_alloc`(). Declared in `<mandoc.h>`, implemented in read.c.
`mparse_copy`()
  Dump a copy of the input to the standard output; used for `-man` `-T` `man`. Declared in `<mandoc.h>`, implemented in read.c.
`mparse_open`()
  Open the file for reading. If that fails and fname does not already end in ‘`.gz`’, try again after appending ‘`.gz`’. Save the information whether the file is zipped or not. Return a file descriptor open for reading or -1 on failure. It can be passed to `mparse_readfd`() or used directly. Declared in `<mandoc.h>`, implemented in read.c.
`mparse_readfd`()
  Parse a file descriptor opened with open(2) or `mparse_open`(). Pass the associated filename in fname. This function may be called multiple times with different parameters; however, close(2) and `mparse_reset`() should be invoked between parses. Declared in `<mandoc.h>`, implemented in read.c.
`mparse_reset`()
  Reset a parser so that `mparse_readfd`() may be used again. Declared in `<mandoc.h>`, implemented in read.c.
`mparse_result`()
  Obtain the result of a parse. Declared in `<mandoc.h>`, implemented in read.c.

## Variables

man_macronames
  The string representation of a man(7) macro as indexed by enum mant.
mdoc_argnames
  The string representation of an mdoc(7) macro argument as indexed by enum mdocargt.
mdoc_macronames
  The string representation of an mdoc(7) macro as indexed by enum mdoct.

# IMPLEMENTATION NOTES

This section consists of structural documentation for mdoc(7) and man(7) syntax trees and strings.

## Man and Mdoc Strings

Strings may be extracted from mdoc and man meta-data, or from text nodes (MDOC_TEXT and MAN_TEXT, respectively). These strings have special non-printing formatting cues embedded in the text itself, as well as roff(7) escapes preserved from input. Implementing systems will need to handle both situations to produce human-readable text. In general, strings may be assumed to consist of 7-bit ASCII characters.

The following non-printing characters may be embedded in text strings:

`ASCII_NBRSP`
  A non-breaking space character.
`ASCII_HYPH`
  A soft hyphen.
`ASCII_BREAK`
  A breakable zero-width space.

Escape characters are also passed verbatim into text strings. An escape character is a sequence of characters beginning with the backslash (‘\’). To construct human-readable text, these should be intercepted with mandoc_escape(3) and converted with one the functions described in mchars_alloc(3).

## Man Abstract Syntax Tree

This AST is governed by the ontological rules dictated in man(7) and derives its terminology accordingly.

The AST is composed of struct roff_node nodes with element, root and text types as declared by the type field. Each node also provides its parse point (the line, pos, and sec fields), its position in the tree (the parent, child, next and prev fields) and some type-specific data.

The tree itself is arranged according to the following normal form, where capitalised non-terminals represent nodes.

ROOT
  ← mnode+
mnode
  ← ELEMENT | TEXT | BLOCK
BLOCK
  ← HEAD BODY
HEAD
  ← mnode*
BODY
  ← mnode*
ELEMENT
  ← ELEMENT | TEXT*
TEXT
  ← [[:ascii:]]*

The only elements capable of nesting other elements are those with next-line scope as documented in man(7).

## Mdoc Abstract Syntax Tree

This AST is governed by the ontological rules dictated in mdoc(7) and derives its terminology accordingly. "In-line" elements described in mdoc(7) are described simply as "elements".

The AST is composed of struct roff_node nodes with block, head, body, element, root and text types as declared by the type field. Each node also provides its parse point (the line, pos, and sec fields), its position in the tree (the parent, child, last, next and prev fields) and some type-specific data, in particular, for nodes generated from macros, the generating macro in the tok field.

The tree itself is arranged according to the following normal form, where capitalised non-terminals represent nodes.

ROOT
  ← mnode+
mnode
  ← BLOCK | ELEMENT | TEXT
BLOCK
  ← HEAD [TEXT] (BODY [TEXT])+ [TAIL [TEXT]]
ELEMENT
  ← TEXT*
HEAD
  ← mnode*
BODY
  ← mnode* [ENDBODY mnode*]
TAIL
  ← mnode*
TEXT
  ← [[:ascii:]]*

Of note are the TEXT nodes following the HEAD, BODY and TAIL nodes of the BLOCK production: these refer to punctuation marks. Furthermore, although a TEXT node will generally have a non-zero-length string, in the specific case of ‘.Bd -literal’, an empty line will produce a zero-length string. Multiple body parts are only found in invocations of ‘Bl -column’, where a new body introduces a new phrase.

The mdoc(7) syntax tree accommodates for broken block structures as well. The ENDBODY node is available to end the formatting associated with a given block before the physical end of that block. It has a non-null end field, is of the BODY type, has the same tok as the BLOCK it is ending, and has a pending field pointing to that BLOCK's BODY node. It is an indirect child of that BODY node and has no children of its own.

An ENDBODY node is generated when a block ends while one of its child blocks is still open, like in the following example:

    .Ao ao
    .Bo bo ac
    .Ac bc
    .Bc end

This example results in the following block structure:

    BLOCK Ao
        HEAD Ao
        BODY Ao
            TEXT ao
            BLOCK Bo, pending -> Ao
                HEAD Bo
                BODY Bo
                    TEXT bo
                    TEXT ac
                    ENDBODY Ao, pending -> Ao
                    TEXT bc
    TEXT end

Here, the formatting of the `Ao` block extends from TEXT ao to TEXT ac, while the formatting of the `Bo` block extends from TEXT bo to TEXT bc. It renders as follows in `-T` `ascii` mode:

`<ao [bo ac> bc] end`

Support for badly-nested blocks is only provided for backward compatibility with some older mdoc(7) implementations. Using badly-nested blocks is strongly discouraged; for example, the `-T` `html` front-end to mandoc(1) is unable to render them in any meaningful way. Furthermore, behaviour when encountering badly-nested blocks is not consistent across troff implementations, especially when using multiple levels of badly-nested blocks.

# SEE ALSO

mandoc(1), man.cgi(3), mandoc_escape(3), mandoc_headers(3), mandoc_malloc(3), mansearch(3), mchars_alloc(3), tbl(3), eqn(7), man(7), mandoc_char(7), mdoc(7), roff(7), tbl(7)

# AUTHORS

The `mandoc` library was written by Kristaps Dzonsons <kristaps@bsd.lv> and is maintained by Ingo Schwarze <schwarze@openbsd.org>.

December 30, 2018 | NetBSD 11.0