отображать системную документацию (display system documentation)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
man — display system documentation
Синопсис (Synopsis)
man [-k] name...
Описание (Description)
The man utility shall write information about each of the name
operands. If name is the name of a standard utility, man at a
minimum shall write a message describing the syntax used by the
standard utility, its options, and operands. If more information
is available, the man utility shall provide it in an
implementation-defined manner.
An implementation may provide information for values of name
other than the standard utilities. Standard utilities that are
listed as optional and that are not supported by the
implementation either shall cause a brief message indicating that
fact to be displayed or shall cause a full display of information
as described previously.
Параметры (Options)
The man utility shall conform to the Base Definitions volume of
POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
The following option shall be supported:
-k Interpret name operands as keywords to be used in
searching a utilities summary database that contains a
brief purpose entry for each standard utility and write
lines from the summary database that match any of the
keywords. The keyword search shall produce results that
are the equivalent of the output of the following
command:
grep -Ei '
name
name
...
' summary-database
This assumes that the summary-database is a text file
with a single entry per line; this organization is not
required and the example using grep -Ei is merely
illustrative of the type of search intended. The purpose
entry to be included in the database shall consist of a
terse description of the purpose of the utility.
Операнды (Operands)
The following operand shall be supported:
name A keyword or the name of a standard utility. When -k is
not specified and name does not represent one of the
standard utilities, the results are unspecified.
Стандартный ввод (Stdin)
Not used.
Входные файлы (Input files)
None.
Переменные окружения (Environment variables)
The following environment variables shall affect the execution of
man:
LANG Provide a default value for the internationalization
variables that are unset or null. (See the Base
Definitions volume of POSIX.1‐2017, Section 8.2,
Internationalization Variables for the precedence of
internationalization variables used to determine the
values of locale categories.)
LC_ALL If set to a non-empty string value, override the values
of all the other internationalization variables.
LC_CTYPE Determine the locale for the interpretation of
sequences of bytes of text data as characters (for
example, single-byte as opposed to multi-byte
characters in arguments and in the summary database).
The value of LC_CTYPE need not affect the format of the
information written about the name operands.
LC_MESSAGES
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to
standard error and informative messages written to
standard output.
NLSPATH Determine the location of message catalogs for the
processing of LC_MESSAGES.
PAGER Determine an output filtering command for writing the
output to a terminal. Any string acceptable as a
command_string operand to the sh -c command shall be
valid. When standard output is a terminal device, the
reference page output shall be piped through the
command. If the PAGER variable is null or not set, the
command shall be either more or another paginator
utility documented in the system documentation.
Асинхронные события (Asynchronous events)
Default.
Стандартный вывод (Stdout)
The man utility shall write text describing the syntax of the
utility name, its options and its operands, or, when -k is
specified, lines from the summary database. The format of this
text is implementation-defined.
Стандартный вывод сообщений (Stderr)
The standard error shall be used for diagnostic messages, and may
also be used for informational messages of unspecified format.
Выходные файлы (Output files)
None.
Расширенное описание (Extended description)
None.
Статус выхода (Exit)
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Последствия ошибок (Consequences of errors)
Default.
The following sections are informative.
Использование в приложениях (Application usage)
None.
Примеры (Examples)
None.
Обоснование (Rationale)
It is recognized that the man utility is only of minimal
usefulness as specified. The opinion of the standard developers
was strongly divided as to how much or how little information man
should be required to provide. They considered, however, that the
provision of some portable way of accessing documentation would
aid user portability. The arguments against a fuller
specification were:
* Large quantities of documentation should not be required on a
system that does not have excess disk space.
* The current manual system does not present information in a
manner that greatly aids user portability.
* A ``better help system'' is currently an area in which
vendors feel that they can add value to their POSIX
implementations.
The -f option was considered, but due to implementation
differences, it was not included in this volume of POSIX.1‐2017.
The description was changed to be more specific about what has to
be displayed for a utility. The standard developers considered it
insufficient to allow a display of only the synopsis without
giving a short description of what each option and operand does.
The ``purpose'' entry to be included in the database can be
similar to the section title (less the numeric prefix) from this
volume of POSIX.1‐2017 for each utility. These titles are
similar to those used in historical systems for this purpose.
See mailx for rationale concerning the default paginator.
The caveat in the LC_CTYPE description was added because it is
not a requirement that an implementation provide reference pages
for all of its supported locales on each system; changing
LC_CTYPE does not necessarily translate the reference page into
another language. This is equivalent to the current state of
LC_MESSAGES in POSIX.1‐2008—locale-specific messages are not yet
a requirement.
The historical MANPATH variable is not included in POSIX because
no attempt is made to specify naming conventions for reference
page files, nor even to mandate that they are files at all. On
some implementations they could be a true database, a hypertext
file, or even fixed strings within the man executable. The
standard developers considered the portability of reference pages
to be outside their scope of work. However, users should be aware
that MANPATH is implemented on a number of historical systems and
that it can be used to tailor the search pattern for reference
pages from the various categories (utilities, functions, file
formats, and so on) when the system administrator reveals the
location and conventions for reference pages on the system.
The keyword search can rely on at least the text of the section
titles from these utility descriptions, and the implementation
may add more keywords. The term ``section titles'' refers to the
strings such as:
man — Display system documentation
ps — Report process status
Будущие направления (Future directions)
None.
Смотри также (See also)
more(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
