The OpenNET Project / Index page

[ новости /+++ | форум | теги | ]

Интерактивная система просмотра системных руководств (man-ов)

 [Cписок руководств | Печать]

vis (3)
  • vis (1) ( FreeBSD man: Команды и прикладные программы пользовательского уровня )
  • >> vis (3) ( FreeBSD man: Библиотечные вызовы )

  • BSD mandoc


     - visually encode characters


    Lb libc


       #include <vis.h>
    char * vis (char *dst int c int flag int nextc);
    int strvis (char *dst const char *src int flag);
    int strvisx (char *dst const char *src size_t len int flag);


    The vis ();
    function copies into Fa dst a string which represents the character Fa c . If Fa c needs no encoding, it is copied in unaltered. The string is null terminated, and a pointer to the end of the string is returned. The maximum length of any encoding is four characters (not including the trailing NUL ) thus, when encoding a set of characters into a buffer, the size of the buffer should be four times the number of characters encoded, plus one for the trailing NUL The Fa flag argument is used for altering the default range of characters considered for encoding and for altering the visual representation. The additional character, Fa nextc , is only used when selecting the VIS_CSTYLE encoding format (explained below).

    The strvis ();
    and strvisx ();
    functions copy into Fa dst a visual representation of the string Fa src . The strvis ();
    function encodes characters from Fa src up to the first NUL The strvisx ();
    function encodes exactly Fa len characters from Fa src (this is useful for encoding a block of data that may contain NUL 's Both forms NUL terminate Fa dst . The size of Fa dst must be four times the number of characters encoded from Fa src (plus one for the NUL ) Both forms return the number of characters in dst (not including the trailing NUL )

    The encoding is a unique, invertible representation composed entirely of graphic characters; it can be decoded back into the original form using the unvis(3) or strunvis(3) functions.

    There are two parameters that can be controlled: the range of characters that are encoded, and the type of representation used. By default, all non-graphic characters except space, tab, and newline are encoded. (See isgraph(3).) The following flags alter this:

    Also encode magic characters `(' * , `?' , `[' and `#' ) recognized by glob(3).
    Also encode space.
    Also encode tab.
    Also encode newline.
    Synonym for VIS_SP | VIS_TAB | VIS_NL
    Only encode "unsafe" characters. Unsafe means control characters which may cause common terminals to perform unexpected functions. Currently this form allows space, tab, newline, backspace, bell, and return - in addition to all graphic characters - unencoded.

    There are four forms of encoding. Most forms use the backslash character `\' to introduce a special sequence; two backslashes are used to represent a real backslash. These are the visual formats:

    Use an `M' to represent meta characters (characters with the 8th bit set), and use caret `^' to represent control characters see ( iscntrl(3)) The following formats are used:

    Represents the control character `C' Spans characters `\000' through `\037' , and `\177' (as `\^?' ) .
    Represents character `C' with the 8th bit set. Spans characters `\241' through `\376'
    Represents control character `C' with the 8th bit set. Spans characters `\200' through `\237' , and `\377' (as `\M^?' ) .
    Represents ASCII space.
    Represents Meta-space.

    Use C-style backslash sequences to represent standard non-printable characters. The following sequences are used to represent the indicated characters:

    BEL (007)
    BS (010)
    NP (014)
    NL (012)
    CR (015)
    SP (040)
    HT (011)
    VT (013)
    NUL (000)

    When using this format, the Fa nextc argument is looked at to determine if a NUL character can be encoded as `\0' instead of `\000' If Fa nextc is an octal digit, the latter representation is used to avoid ambiguity.

    Use URI encoding as described in RFC 1808. The form is `%dd' where d represents a hexadecimal digit.
    Use a three digit octal sequence. The form is `\ddd' where d represents an octal digit.

    There is one additional flag, VIS_NOSLASH which inhibits the doubling of backslashes and the backslash before the default format (that is, control characters are represented by `^C' and meta characters as `M-C' ) . With this flag set, the encoding is ambiguous and non-invertible.  


    unvis(1), unvis(3)
    R. Fielding Relative Uniform Resource Locators RFC1808


    These functions first appeared in BSD 4.4  


    The family of functions do not recognize multibyte characters, and thus may consider them to be non-printable when they are in fact printable (and vice versa.)




    Поиск по тексту MAN-ов: 

    Inferno Solutions
    Hosting by

    Закладки на сайте
    Проследить за страницей
    Created 1996-2024 by Maxim Chirkov
    Добавить, Поддержать, Вебмастеру