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MANDOC(3)

Library Functions Manual

MANDOC(3)

NAME

mandoc, man_deroff, man_meta, man_mparse, man_node, mdoc_deroff, mdoc_meta, mdoc_node, mparse_alloc, mparse_free, mparse_getkeep, mparse_keep, mparse_open, mparse_readfd, mparse_reset, mparse_result, mparse_strerror, mparse_strlevel mparse_wait, — mandoc macro compiler library

SYNOPSIS

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

#define ASCII_NBRSP
#define ASCII_HYPH
#define ASCII_BREAK

struct mparse *
mparse_alloc(int options, enum mandoclevel wlevel, mandocmsg mmsg, const struct mchars *mchars, char *defos);

void
(*mandocmsg)(enum mandocerr errtype, enum mandoclevel level, const char *file, int line, int col, const char *msg);

void
mparse_free(struct mparse *parse);

const char *
mparse_getkeep(const struct mparse *parse);

void
mparse_keep(struct mparse *parse);

enum mandoclevel
mparse_open(struct mparse *parse, int *fd, const char *fname);

enum mandoclevel
mparse_readfd(struct mparse *parse, int fd, const char *fname);

void
mparse_reset(struct mparse *parse);

void
mparse_result(struct mparse *parse, struct mdoc **mdoc, struct man **man, char **sodest);

const char *
mparse_strerror(enum mandocerr);

const char *
mparse_strlevel(enum mandoclevel);

enum mandoclevel
mparse_wait(struct mparse *parse);

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

void
mdoc_deroff(char **dest, const struct mdoc_node *node);

const struct mdoc_meta *
mdoc_meta(const struct mdoc *mdoc);

const struct mdoc_node *
mdoc_node(const struct mdoc *mdoc);

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

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

void
man_deroff(char **dest, const struct man_node *node);

const struct man_meta *
man_meta(const struct man *man);

const struct mparse *
man_mparse(const struct man *man);

const struct man_node *
man_node(const struct man *man);

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:

initiate a parsing sequence with mchars_alloc(3) and mparse_alloc();
open a file with open(2) or mparse_open();
parse it with mparse_readfd();
retrieve the syntax tree with mparse_result();
iterate over parse nodes with mdoc_node() or man_node();
free all allocated memory with mparse_free() and mchars_free(3), or invoke mparse_reset() and 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.
struct mchars: An opaque pointer to a a character table. Created with mchars_alloc(3) and freed with mchars_free(3).
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.
mandocmsg: A prototype for a function to handle error and warning messages emitted by the parser.

Functions

man_deroff()

Obtain a text-only representation of a struct man_node, including text contained in its child nodes. To be used on children of the pointer returned from man_node(). When it is no longer needed, the pointer returned from man_deroff() can be passed to free(3).

man_meta()

Obtain the meta-data of a successful man(7) parse. This may only be used on a pointer returned by mparse_result(). Declared in <man.h>, implemented in man.c.

man_mparse()

Get the parser used for the current output. Declared in <man.h>, implemented in man.c.

man_node()

Obtain the root node of a successful man(7) parse. This may only be used on a pointer returned by mparse_result(). Declared in <man.h>, implemented in man.c.

mdoc_deroff()

Obtain a text-only representation of a struct mdoc_node, including text contained in its child nodes. To be used on children of the pointer returned from mdoc_node(). When it is no longer needed, the pointer returned from mdoc_deroff() can be passed to free(3).

mdoc_meta()

Obtain the meta-data of a successful mdoc parse. This may only be used on a pointer returned by mparse_result(). Declared in <mdoc.h>, implemented in mdoc.c.

mdoc_node()

Obtain the root node of a successful mdoc parse. This may only be used on a pointer returned by mparse_result(). Declared in <mdoc.h>, implemented in mdoc.c.

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 argument of mparse_result().
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.
wlevel: Can be set to MANDOCLEVEL_BADARG, MANDOCLEVEL_ERROR, or MANDOCLEVEL_WARNING. Messages below the selected level will be suppressed.
mmsg: A callback function to handle errors and warnings. See main.c for an example.
mchars: An opaque pointer to a a character table obtained from mchars_alloc(3).
defos: A default string for the mdoc(7) ‘Os’ macro, overriding the OSNAME preprocessor definition and the results of uname(3).

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_getkeep()

Acquire the keep buffer. Must follow a call of mparse_keep(). Declared in <mandoc.h>, implemented in read.c.

mparse_keep()

Instruct the parser to retain a copy of its parsed input. This can be acquired with subsequent mparse_getkeep() calls. Declared in <mandoc.h>, implemented in read.c.

mparse_open()

If the fname ends in .gz, open with gunzip(1); otherwise, with open(2). If open(2) fails, append .gz and try with gunzip(1). Return a file descriptor open for reading in fd, 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. Calls mparse_wait() before returning. This function may be called multiple times with different parameters; however, 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. One of the three pointers will be filled in. Declared in <mandoc.h>, implemented in read.c.

mparse_strerror()

Return a statically-allocated string representation of an error code. Declared in <mandoc.h>, implemented in read.c.

mparse_strlevel()

Return a statically-allocated string representation of a level code. Declared in <mandoc.h>, implemented in read.c.

mparse_wait()

Bury a gunzip(1) child process that was spawned with mparse_open(). To be called after the parse sequence is complete. Not needed after mparse_readfd(), but does no harm in that case, either. Returns MANDOCLEVEL_OK on success and MANDOCLEVEL_SYSERR on failure, that is, when wait(2) fails, or when gunzip(1) died from a signal or exited with non-zero status. Declared in <mandoc.h>, implemented in read.c.

Variables

man_macronames: The string representation of a man macro as indexed by enum mant.
mdoc_argnames: The string representation of a mdoc macro argument as indexed by enum mdocargt.
mdoc_macronames: The string representation of a mdoc 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 man_node nodes with element, root and text types as declared by the type field. Each node also provides its parse point (the line, sec, and pos 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 mdoc_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, sec, and pos fields), its position in the tree (the parent, child, nchild, 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 -Tascii 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 -Thtml and -Txhtml front-ends to mandoc(1) are 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.

AUTHORS

The mandoc library was written by Kristaps Dzonsons <kristaps@bsd.lv>.

January 15, 2015

Debian