Sortix cisortix manual

This manual documents Sortix cisortix. You can instead view this document in the latest official manual.

NAME

mandoc — format and display UNIX manuals

SYNOPSIS

mandoc [-acfhkl] [-Ios=name] [-Kencoding] [-mformat] [-Ooption] [-Toutput] [-Wlevel] [file ...]

DESCRIPTION

The mandoc utility formats UNIX manual pages for display.

By default, mandoc reads mdoc(7) or man(7) text from stdin, implying -mandoc, and produces -Tlocale output.

The options are as follows:

In -f and -k mode, mandoc also supports the options -CMmOSsw described in the apropos(1) manual.

Input Formats

The mandoc utility accepts mdoc(7) and man(7) input with -mdoc and -man, respectively. The mdoc(7) format is strongly recommended; man(7) should only be used for legacy manuals.

A third option, -mandoc, which is also the default, determines encoding on-the-fly: if the first non-comment macro is ‘Dd’ or ‘Dt’, the mdoc(7) parser is used; otherwise, the man(7) parser is used.

If multiple files are specified with -mandoc, each has its file-type determined this way. If multiple files are specified and -mdoc or -man is specified, then this format is used exclusively.

Output Formats

The mandoc utility accepts the following -T arguments, which correspond to output modes:

If multiple input files are specified, these will be processed by the corresponding filter in-order.

ASCII Output

Output produced by -Tascii is rendered in standard 7-bit ASCII documented in ascii(7).

Font styles are applied by using back-spaced encoding such that an underlined character ‘c’ is rendered as ‘_\[bs]c’, where ‘\[bs]’ is the back-space character number 8. Emboldened characters are rendered as ‘c\[bs]c’.

The special characters documented in mandoc_char(7) are rendered best-effort in an ASCII equivalent.

Output width is limited to 78 visible columns unless literal input lines exceed this limit.

The following -O arguments are accepted:

HTML Output

Output produced by -Thtml conforms to HTML5 using optional self-closing tags. Default styles use only CSS1. Equations rendered from eqn(7) blocks use MathML.

The example.style.css file documents style-sheet classes available for customising output. If a style-sheet is not specified with -Ostyle, -Thtml defaults to simple output (via an embedded style-sheet) readable in any graphical or text-based web browser.

Special characters are rendered in decimal-encoded UTF-8.

The following -O arguments are accepted:

Locale Output

Locale-depending output encoding is triggered with -Tlocale. This is the default.

This option is not available on all systems: systems without locale support, or those whose internal representation is not natively UCS-4, will fall back to -Tascii. See ASCII Output for font style specification and available command-line arguments.

Man Output

Translate input format into man(7) output format. This is useful for distributing manual sources to legacy systems lacking mdoc(7) formatters.

If mdoc(7) is passed as input, it is translated into man(7). If the input format is man(7), the input is copied to the output, expanding any roff(7) ‘so’ requests. The parser is also run, and as usual, the -W level controls which DIAGNOSTICS are displayed before copying the input to the output.

PDF Output

PDF-1.1 output may be generated by -Tpdf. See PostScript Output for -O arguments and defaults.

PostScript Output

PostScript “Adobe-3.0” Level-2 pages may be generated by -Tps. Output pages default to letter sized and are rendered in the Times font family, 11-point. Margins are calculated as 1/9 the page length and width. Line-height is 1.4m.

Special characters are rendered as in ASCII Output.

The following -O arguments are accepted:

UTF-8 Output

Use -Tutf8 to force a UTF-8 locale. See Locale Output for details and options.

ENVIRONMENT

EXIT STATUS

The mandoc utility exits with one of the following values, controlled by the message level associated with the -W option:

Note that selecting -Tlint output mode implies -Wwarning.

EXAMPLES

To page manuals to the terminal:

$ mandoc -Wall,stop mandoc.1 2>&1 | less

$ mandoc mandoc.1 mdoc.3 mdoc.7 | less

To produce HTML manuals with style.css as the style-sheet:

$ mandoc -Thtml -Ostyle=style.css mdoc.7 > mdoc.7.html

To check over a large set of manuals:

$ mandoc -Tlint `find /usr/src -name \*\.[1-9]`

To produce a series of PostScript manuals for A4 paper:

$ mandoc -Tps -Opaper=a4 mdoc.7 man.7 > manuals.ps

Convert a modern mdoc(7) manual to the older man(7) format, for use on systems lacking an mdoc(7) parser:

$ mandoc -Tman foo.mdoc > foo.man

DIAGNOSTICS

Messages displayed by mandoc follow this format:

mandoc: file:line:column: level: message: macro args

Line and column numbers start at 1. Both are omitted for messages referring to an input file as a whole. Macro names and arguments are omitted where meaningless. Fatal messages about invalid command line arguments or operating system errors, for example when memory is exhausted, may also omit the file and level fields.

Message levels have the following meanings:

Messages of the warning, error, and unsupp levels except those about non-existent or unreadable input files are hidden unless their level, or a lower level, is requested using a -W option or -Tlint output mode.

missing manual title, using UNTITLED: (mdoc) A Dt macro has no arguments, or there is no Dt macro before the first non-prologue macro.
missing manual title, using "": (man) There is no TH macro, or it has no arguments.
lower case character in document title: (mdoc, man) The title is still used as given in the Dt or TH macro.
missing manual section, using "": (mdoc, man) A Dt or TH macro lacks the mandatory section argument.
unknown manual section: (mdoc) The section number in a Dt line is invalid, but still used.
missing date, using today's date: (mdoc, man) The document was parsed as mdoc(7) and it has no Dd macro, or the Dd macro has no arguments or only empty arguments; or the document was parsed as man(7) and it has no TH macro, or the TH macro has less than three arguments or its third argument is empty.
cannot parse date, using it verbatim: (mdoc, man) The date given in a Dd or TH macro does not follow the conventional format.
missing Os macro, using "": (mdoc) The default or current system is not shown in this case.
duplicate prologue macro: (mdoc) One of the prologue macros occurs more than once. The last instance overrides all previous ones.
late prologue macro: (mdoc) A Dd or Os macro occurs after some non-prologue macro, but still takes effect.
skipping late title macro: (mdoc) The Dt macro appears after the first non-prologue macro. Traditional formatters cannot handle this because they write the page header before parsing the document body. Even though this technical restriction does not apply to mandoc, traditional semantics is preserved. The late macro is discarded including its arguments.
prologue macros out of order: (mdoc) The prologue macros are not given in the conventional order Dd, Dt, Os. All three macros are used even when given in another order.

Warnings regarding document structure

.so is fragile, better use ln(1): (roff) Including files only works when the parser program runs with the correct current working directory.
no document body: (mdoc, man) The document body contains neither text nor macros. An empty document is shown, consisting only of a header and a footer line.
content before first section header: (mdoc, man) Some macros or text precede the first Sh or SH section header. The offending macros and text are parsed and added to the top level of the syntax tree, outside any section block.
first section is not NAME: (mdoc) The argument of the first Sh macro is not ‘NAME’. This may confuse makewhatis(8) and apropos(1).
NAME section without name: (mdoc) The NAME section does not contain any Nm child macro.
NAME section without description: (mdoc) The NAME section lacks the mandatory Nd child macro.
description not at the end of NAME: (mdoc) The NAME section does contain an Nd child macro, but other content follows it.
bad NAME section content: (mdoc) The NAME section contains plain text or macros other than Nm and Nd.
missing description line, using "": (mdoc) The Nd macro lacks the required argument. The title line of the manual will end after the dash.
sections out of conventional order: (mdoc) A standard section occurs after another section it usually precedes. All section titles are used as given, and the order of sections is not changed.
duplicate section title: (mdoc) The same standard section title occurs more than once.
unexpected section: (mdoc) A standard section header occurs in a section of the manual where it normally isn't useful.
unusual Xr order: (mdoc) In the SEE ALSO section, an Xr macro with a lower section number follows one with a higher number, or two Xr macros refering to the same section are out of alphabetical order.
unusual Xr punctuation: (mdoc) In the SEE ALSO section, punctuation between two Xr macros differs from a single comma, or there is trailing punctuation after the last Xr macro.
AUTHORS section without An macro: (mdoc) An AUTHORS sections contains no An macros, or only empty ones. Probably, there are author names lacking markup.

obsolete macro

(mdoc) See the mdoc(7) manual for replacements.

macro neither callable nor escaped

(mdoc) The name of a macro that is not callable appears on a macro line. It is printed verbatim. If the intention is to call it, move it to its own input line; otherwise, escape it by prepending ‘\&’.

skipping paragraph macro

In mdoc(7) documents, this happens

at the beginning and end of sections and subsections
right before non-compact lists and displays
at the end of items in non-column, non-compact lists
and for multiple consecutive paragraph macros.

In man(7) documents, it happens

for empty P, PP, and LP macros
for IP macros having neither head nor body arguments
for br or sp right after SH or SS

moving paragraph macro out of list

(mdoc) A list item in a Bl list contains a trailing paragraph macro. The paragraph macro is moved after the end of the list.

skipping no-space macro

(mdoc) An input line begins with an Ns macro. The macro is ignored.

blocks badly nested

(mdoc) If two blocks intersect, one should completely contain the other. Otherwise, rendered output is likely to look strange in any output format, and rendering in SGML-based output formats is likely to be outright wrong because such languages do not support badly nested blocks at all. Typical examples of badly nested blocks are “Ao Bo Ac Bc” and “Ao Bq Ac”. In these examples, Ac breaks Bo and Bq, respectively.

nested displays are not portable

(mdoc) A Bd, D1, or Dl display occurs nested inside another Bd display. This works with mandoc, but fails with most other implementations.

moving content out of list

(mdoc) A Bl list block contains text or macros before the first It macro. The offending children are moved before the beginning of the list.

.Vt block has child macro

(mdoc) The Vt macro supports plain text arguments only. Formatting may be ugly and semantic searching for the affected content might not work.

fill mode already enabled, skipping

(man) A fi request occurs even though the document is still in fill mode, or already switched back to fill mode. It has no effect.

fill mode already disabled, skipping

(man) An nf request occurs even though the document already switched to no-fill mode and did not switch back to fill mode yet. It has no effect.

line scope broken

(man) While parsing the next-line scope of the previous macro, another macro is found that prematurely terminates the previous one. The previous, interrupted macro is deleted from the parse tree.

skipping empty request

(roff, eqn) The macro name is missing from a macro definition request, or an eqn(7) control statement or operation keyword lacks its required argument.

conditional request controls empty scope

(roff) A conditional request is only useful if any of the following follows it on the same logical input line:

The ‘\{’ keyword to open a multi-line scope.
A request or macro or some text, resulting in a single-line scope.
The immediate end of the logical line without any intervening whitespace, resulting in next-line scope.

Here, a conditional request is followed by trailing whitespace only, and there is no other content on its logical input line. Note that it doesn't matter whether the logical input line is split across multiple physical input lines using ‘\’ line continuation characters. This is one of the rare cases where trailing whitespace is syntactically significant. The conditional request controls a scope containing whitespace only, so it is unlikely to have a significant effect, except that it may control a following el clause.

skipping empty macro

(mdoc) The indicated macro has no arguments and hence no effect.

empty block

(mdoc, man) A Bd, Bk, Bl, D1, Dl, RS, or UR block contains nothing in its body and will produce no output.

empty argument, using 0n

(mdoc) The required width is missing after Bd or Bl -offset or -width.

missing display type, using -ragged

(mdoc) The Bd macro is invoked without the required display type.

list type is not the first argument

(mdoc) In a Bl macro, at least one other argument precedes the type argument. The mandoc utility copes with any argument order, but some other mdoc(7) implementations do not.

missing -width in -tag list, using 8n

(mdoc) Every Bl macro having the -tag argument requires -width, too.

missing utility name, using ""

(mdoc) The Ex -std macro is called without an argument before Nm has first been called with an argument.

missing function name, using ""

(mdoc) The Fo macro is called without an argument. No function name is printed.

empty head in list item

(mdoc) In a Bl -diag, -hang, -inset, -ohang, or -tag list, an It macro lacks the required argument. The item head is left empty.

empty list item

(mdoc) In a Bl -bullet, -dash, -enum, or -hyphen list, an It block is empty. An empty list item is shown.

missing font type, using \fR

(mdoc) A Bf macro has no argument. It switches to the default font.

unknown font type, using \fR

(mdoc) The Bf argument is invalid. The default font is used instead.

nothing follows prefix

(mdoc) A Pf macro has no argument, or only one argument and no macro follows on the same input line. This defeats its purpose; in particular, spacing is not suppressed before the text or macros following on the next input line.

empty reference block

(mdoc) An Rs macro is immediately followed by an Re macro on the next input line. Such an empty block does not produce any output.

missing -std argument, adding it

(mdoc) An Ex or Rv macro lacks the required -std argument. The mandoc utility assumes -std even when it is not specified, but other implementations may not.

missing option string, using ""

(man) The OP macro is invoked without any argument. An empty pair of square brackets is shown.

missing resource identifier, using ""

(man) The UR macro is invoked without any argument. An empty pair of angle brackets is shown.

missing eqn box, using ""

(eqn) A diacritic mark or a binary operator is found, but there is nothing to the left of it. An empty box is inserted.

unterminated quoted argument: (roff) Macro arguments can be enclosed in double quote characters such that space characters and macro names contained in the quoted argument need not be escaped. The closing quote of the last argument of a macro can be omitted. However, omitting it is not recommended because it makes the code harder to read.
duplicate argument: (mdoc) A Bd or Bl macro has more than one -compact, more than one -offset, or more than one -width argument. All but the last instances of these arguments are ignored.
skipping duplicate argument: (mdoc) An An macro has more than one -split or -nosplit argument. All but the first of these arguments are ignored.
skipping duplicate display type: (mdoc) A Bd macro has more than one type argument; the first one is used.
skipping duplicate list type: (mdoc) A Bl macro has more than one type argument; the first one is used.
skipping -width argument: (mdoc) A Bl -column, -diag, -ohang, -inset, or -item list has a -width argument. That has no effect.
wrong number of cells: In a line of a Bl -column list, the number of tabs or Ta macros is less than the number expected from the list header line or exceeds the expected number by more than one. Missing cells remain empty, and all cells exceeding the number of columns are joined into one single cell.
unknown AT&T UNIX version: (mdoc) An At macro has an invalid argument. It is used verbatim, with “AT&T UNIX ” prefixed to it.
comma in function argument: (mdoc) An argument of an Fa or Fn macro contains a comma; it should probably be split into two arguments.
parenthesis in function name: (mdoc) The first argument of an Fc or Fn macro contains an opening or closing parenthesis; that's probably wrong, parentheses are added automatically.
invalid content in Rs block: (mdoc) An Rs block contains plain text or non-% macros. The bogus content is left in the syntax tree. Formatting may be poor.
invalid Boolean argument: (mdoc) An Sm macro has an argument other than on or off. The invalid argument is moved out of the macro, which leaves the macro empty, causing it to toggle the spacing mode.
unknown font, skipping request: (man, tbl) A roff(7) ft request or a tbl(7) f layout modifier has an unknown font argument.
odd number of characters in request: (roff) A tr request contains an odd number of characters. The last character is mapped to the blank character.

blank line in fill mode, using .sp: (mdoc) The meaning of blank input lines is only well-defined in non-fill mode: In fill mode, line breaks of text input lines are not supposed to be significant. However, for compatibility with groff, blank lines in fill mode are replaced with sp requests.
tab in filled text: (mdoc, man) The meaning of tab characters is only well-defined in non-fill mode: In fill mode, whitespace is not supposed to be significant on text input lines. As an implementation dependent choice, tab characters on text lines are passed through to the formatters in any case. Given that the text before the tab character will be filled, it is hard to predict which tab stop position the tab will advance to.
whitespace at end of input line: (mdoc, man, roff) Whitespace at the end of input lines is almost never semantically significant — but in the odd case where it might be, it is extremely confusing when reviewing and maintaining documents.
bad comment style: (roff) Comment lines start with a dot, a backslash, and a double-quote character. The mandoc utility treats the line as a comment line even without the backslash, but leaving out the backslash might not be portable.
invalid escape sequence: (roff) An escape sequence has an invalid opening argument delimiter, lacks the closing argument delimiter, or the argument has too few characters. If the argument is incomplete, \* and \n expand to an empty string, \B to the digit ‘0’, and \w to the length of the incomplete argument. All other invalid escape sequences are ignored.
undefined string, using "": (roff) If a string is used without being defined before, its value is implicitly set to the empty string. However, defining strings explicitly before use keeps the code more readable.

tbl line starts with span: (tbl) The first cell in a table layout line is a horizontal span (‘s’). Data provided for this cell is ignored, and nothing is printed in the cell.
tbl column starts with span: (tbl) The first line of a table layout specification requests a vertical span (‘^’). Data provided for this cell is ignored, and nothing is printed in the cell.
skipping vertical bar in tbl layout: (tbl) A table layout specification contains more than two consecutive vertical bars. A double bar is printed, all additional bars are discarded.

non-alphabetic character in tbl options: (tbl) The table options line contains a character other than a letter, blank, or comma where the beginning of an option name is expected. The character is ignored.
skipping unknown tbl option: (tbl) The table options line contains a string of letters that does not match any known option name. The word is ignored.
missing tbl option argument: (tbl) A table option that requires an argument is not followed by an opening parenthesis, or the opening parenthesis is immediately followed by a closing parenthesis. The option is ignored.
wrong tbl option argument size: (tbl) A table option argument contains an invalid number of characters. Both the option and the argument are ignored.
empty tbl layout: (tbl) A table layout specification is completely empty, specifying zero lines and zero columns. As a fallback, a single left-justified column is used.
invalid character in tbl layout: (tbl) A table layout specification contains a character that can neither be interpreted as a layout key character nor as a layout modifier, or a modifier precedes the first key. The invalid character is discarded.
unmatched parenthesis in tbl layout: (tbl) A table layout specification contains an opening parenthesis, but no matching closing parenthesis. The rest of the input line, starting from the parenthesis, has no effect.
tbl without any data cells: (tbl) A table does not contain any data cells. It will probably produce no output.
ignoring data in spanned tbl cell: (tbl) A table cell is marked as a horizontal span (‘s’) or vertical span (‘^’) in the table layout, but it contains data. The data is ignored.
ignoring extra tbl data cells: (tbl) A data line contains more cells than the corresponding layout line. The data in the extra cells is ignored.
data block open at end of tbl: (tbl) A data block is opened with T{, but never closed with a matching T}. The remaining data lines of the table are all put into one cell, and any remaining cells stay empty.

input stack limit exceeded, infinite loop?

(roff) Explicit recursion limits are implemented for the following features, in order to prevent infinite loops:

expansion of nested escape sequences including expansion of strings and number registers,
expansion of nested user-defined macros,
and so file inclusion.

When a limit is hit, the output is incorrect, typically losing some content, but the parser can continue.

skipping bad character

(mdoc, man, roff) The input file contains a byte that is not a printable ascii(7) character. The message mentions the character number. The offending byte is replaced with a question mark (‘?’). Consider editing the input file to replace the byte with an ASCII transliteration of the intended character.

skipping unknown macro

(mdoc, man, roff) The first identifier on a request or macro line is neither recognized as a roff(7) request, nor as a user-defined macro, nor, respectively, as an mdoc(7) or man(7) macro. It may be mistyped or unsupported. The request or macro is discarded including its arguments.

skipping insecure request

(roff) An input file attempted to run a shell command or to read or write an external file. Such attempts are denied for security reasons.

skipping item outside list

(mdoc, eqn) An It macro occurs outside any Bl list, or an eqn(7) above delimiter occurs outside any pile. It is discarded including its arguments.

skipping column outside column list

(mdoc) A Ta macro occurs outside any Bl -column block. It is discarded including its arguments.

skipping end of block that is not open

(mdoc, man, eqn, tbl, roff) Various syntax elements can only be used to explicitly close blocks that have previously been opened. An mdoc(7) block closing macro, a man(7) RE or UE macro, an eqn(7) right delimiter or closing brace, or the end of an equation, table, or roff(7) conditional request is encountered but no matching block is open. The offending request or macro is discarded.

fewer RS blocks open, skipping

(man) The RE macro is invoked with an argument, but less than the specified number of RS blocks is open. The RE macro is discarded.

inserting missing end of block

(mdoc, tbl) Various mdoc(7) macros as well as tables require explicit closing by dedicated macros. A block that doesn't support bad nesting ends before all of its children are properly closed. The open child nodes are closed implicitly.

appending missing end of block

(mdoc, man, eqn, tbl, roff) At the end of the document, an explicit mdoc(7) block, a man(7) next-line scope or RS or UR block, an equation, table, or roff(7) conditional or ignore block is still open. The open block is closed implicitly.

escaped character not allowed in a name

(roff) Macro, string and register identifiers consist of printable, non-whitespace ASCII characters. Escape sequences and characters and strings expressed in terms of them cannot form part of a name. The first argument of an am, as, de, ds, nr, or rr request, or any argument of an rm request, or the name of a request or user defined macro being called, is terminated by an escape sequence. In the cases of as, ds, and nr, the request has no effect at all. In the cases of am, de, rr, and rm, what was parsed up to this point is used as the arguments to the request, and the rest of the input line is discarded including the escape sequence. When parsing for a request or a user-defined macro name to be called, only the escape sequence is discarded. The characters preceding it are used as the request or macro name, the characters following it are used as the arguments to the request or macro.

NOT IMPLEMENTED: Bd -file

(mdoc) For security reasons, the Bd macro does not support the -file argument. By requesting the inclusion of a sensitive file, a malicious document might otherwise trick a privileged user into inadvertently displaying the file on the screen, revealing the file content to bystanders. The argument is ignored including the file name following it.

missing list type, using -item

(mdoc) A Bl macro fails to specify the list type.

missing manual name, using ""

(mdoc) The first call to Nm lacks the required argument.

uname(3) system call failed, using UNKNOWN

(mdoc) The Os macro is called without arguments, and the uname(3) system call failed. As a workaround, mandoc can be compiled with -DOSNAME="\"string\"".

unknown standard specifier

(mdoc) An St macro has an unknown argument and is discarded.

skipping request without numeric argument

(roff, eqn) An it request or an eqn(7) size or gsize statement has a non-numeric or negative argument or no argument at all. The invalid request or statement is ignored.

NOT IMPLEMENTED: .so with absolute path or ".."

(roff) For security reasons, mandoc allows so file inclusion requests only with relative paths and only without ascending to any parent directory. By requesting the inclusion of a sensitive file, a malicious document might otherwise trick a privileged user into inadvertently displaying the file on the screen, revealing the file content to bystanders. mandoc only shows the path as it appears behind so.

.so request failed

(roff) Servicing a so request requires reading an external file, but the file could not be opened. mandoc only shows the path as it appears behind so.

skipping all arguments

(mdoc, man, eqn, roff) An mdoc(7) Bt, Ed, Ef, Ek, El, Lp, Pp, Re, Rs, or Ud macro, an It macro in a list that don't support item heads, a man(7) LP, P, or PP macro, an eqn(7) EQ or EN macro, or a roff(7) br, fi, or nf request or ‘..’ block closing request is invoked with at least one argument. All arguments are ignored.

skipping excess arguments

(mdoc, man, roff) A macro or request is invoked with too many arguments:

Fo, PD, RS, UR, ft, or sp with more than one argument
An with another argument after -split or -nosplit
RE with more than one argument or with a non-integer argument
OP or a request of the de family with more than two arguments
Dt with more than three arguments
TH with more than five arguments
Bd, Bk, or Bl with invalid arguments

The excess arguments are ignored.

Unsupported features

input too large: (mdoc, man) Currently, mandoc cannot handle input files larger than its arbitrary size limit of 2^31 bytes (2 Gigabytes). Since useful manuals are always small, this is not a problem in practice. Parsing is aborted as soon as the condition is detected.
unsupported control character: (roff) An ASCII control character supported by other roff(7) implementations but not by mandoc was found in an input file. It is replaced by a question mark.
unsupported roff request: (roff) An input file contains a roff(7) request supported by GNU troff or Heirloom troff but not by mandoc, and it is likely that this will cause information loss or considerable misformatting.
eqn delim option in tbl: (eqn, tbl) The options line of a table defines equation delimiters. Any equation source code contained in the table will be printed unformatted.
unsupported table layout modifier: (tbl) A table layout specification contains an ‘m’ modifier. The modifier is discarded.
ignoring macro in table: (tbl, mdoc, man) A table contains an invocation of an mdoc(7) or man(7) macro or of an undefined macro. The macro is ignored, and its arguments are handled as if they were a text line.

AUTHORS

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

BUGS

In -Thtml, the maximum size of an element attribute is determined by BUFSIZ, which is usually 1024 bytes. Be aware of this when setting long link formats such as -Ostyle=really/long/link.