man

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. 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. Provide a default value for the internationalization variables that are unset or null. (See XBD Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) If set to a non-empty string value, override the values of all the other internationalization variables. 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. 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. [XSI) ] ![[Option Start]]( Determine the location of message catalogs for the processing of LC MESSAGES. ![[Option End]]( 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. The standard error shall be used for diagnostic messages, and may also be used for informational messages of unspecified format. 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 "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. 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.1-2017-locale-specific messages are not yet a requirement. Austin Group Interpretation 1003.1-2001 108 is applied, clarifying that informational messages may appear on standard error.