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30 .\" @(#)vis.3 8.1 (Berkeley) 6/9/93
51 .Nd visually encode characters
57 .Fn vis "char *dst" "int c" "int flag" "int nextc"
59 .Fn nvis "char *dst" "size_t dlen" "int c" "int flag" "int nextc"
61 .Fn strvis "char *dst" "const char *src" "int flag"
63 .Fn stravis "char **dst" "const char *src" "int flag"
65 .Fn strnvis "char *dst" "const char *src" "size_t len" "int flag"
67 .Fn strvisx "char *dst" "const char *src" "size_t len" "int flag"
69 .Fn strnvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag"
71 .Fn strenvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" "int *cerr_ptr"
73 .Fn svis "char *dst" "int c" "int flag" "int nextc" "const char *extra"
75 .Fn snvis "char *dst" "size_t dlen" "int c" "int flag" "int nextc" "const char *extra"
77 .Fn strsvis "char *dst" "const char *src" "int flag" "const char *extra"
79 .Fn strsnvis "char *dst" "size_t dlen" "const char *src" "int flag" "const char *extra"
81 .Fn strsvisx "char *dst" "const char *src" "size_t len" "int flag" "const char *extra"
83 .Fn strsnvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" "const char *extra"
85 .Fn strsenvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" "const char *extra" "int *cerr_ptr"
92 a string which represents the character
96 needs no encoding, it is copied in unaltered.
97 The string is null terminated, and a pointer to the end of the string is
99 The maximum length of any encoding is four
100 bytes (not including the trailing
103 encoding a set of characters into a buffer, the size of the buffer should
104 be four times the number of bytes encoded, plus one for the trailing
106 The flag parameter is used for altering the default range of
107 characters considered for encoding and for altering the visual
109 The additional character,
111 is only used when selecting the
113 encoding format (explained below).
124 a visual representation of
131 functions encode characters from
140 functions encode exactly
145 is useful for encoding a block of data that may contain
153 must be four times the number
154 of bytes encoded from
159 forms return the number of characters in
161 (not including the trailing
165 function allocates space dynamically to hold the string.
168 versions of the functions also take an additional argument
170 that indicates the length of the
175 is not large enough to fit the converted string then the
179 functions return \-1 and set
185 function takes an additional argument,
187 that is used to pass in and out a multibyte conversion error flag.
188 This is useful when processing single characters at a time when
189 it is possible that the locale may be set to something other
190 than the locale of the characters in the input data.
210 but have an additional argument
214 terminated list of characters.
215 These characters will be copied encoded or backslash-escaped into
217 These functions are useful e.g. to remove the special meaning
218 of certain characters to shells.
220 The encoding is a unique, invertible representation composed entirely of
221 graphic characters; it can be decoded back into the original form using
229 There are two parameters that can be controlled: the range of
230 characters that are encoded (applies only to
238 and the type of representation used.
239 By default, all non-graphic characters,
240 except space, tab, and newline are encoded (see
244 .Bl -tag -width VIS_WHITEX
246 Also encode double quotes
248 Also encode the magic characters
257 Also encode the meta characters used by shells (in addition to the glob
284 .Dv VIS_SP | VIS_TAB | VIS_NL .
287 .Dv VIS_WHITE | VIS_GLOB | VIS_SHELL .
292 Unsafe means control characters which may cause common terminals to perform
293 unexpected functions.
294 Currently this form allows space, tab, newline, backspace, bell, and
295 return \(em in addition to all graphic characters \(em unencoded.
298 (The above flags have no effect for
306 When using these functions, place all graphic characters to be
307 encoded in an array pointed to by
309 In general, the backslash character should be included in this array, see the
310 warning on the use of the
314 There are six forms of encoding.
315 All forms use the backslash character
317 to introduce a special
318 sequence; two backslashes are used to represent a real backslash,
327 These are the visual formats:
328 .Bl -tag -width VIS_CSTYLE
332 to represent meta characters (characters with the 8th
333 bit set), and use caret
335 to represent control characters (see
337 The following formats are used:
338 .Bl -tag -width xxxxx
340 Represents the control character
353 with the 8th bit set.
359 Represents control character
361 with the 8th bit set.
375 Represents Meta-space.
378 Use C-style backslash sequences to represent standard non-printable
380 The following sequences are used to represent the indicated characters:
381 .Bd -unfilled -offset indent
382 .Li \ea Tn \(em BEL No (007)
383 .Li \eb Tn \(em BS No (010)
384 .Li \ef Tn \(em NP No (014)
385 .Li \en Tn \(em NL No (012)
386 .Li \er Tn \(em CR No (015)
387 .Li \es Tn \(em SP No (040)
388 .Li \et Tn \(em HT No (011)
389 .Li \ev Tn \(em VT No (013)
390 .Li \e0 Tn \(em NUL No (000)
393 When using this format, the
395 parameter is looked at to determine if a
397 character can be encoded as
403 is an octal digit, the latter representation is used to
406 Non-printable characters without C-style
407 backslash sequences use the default representation.
409 Use a three digit octal sequence.
414 represents an octal digit.
415 .It Dv VIS_CSTYLE \&| Dv VIS_OCTAL
418 except that non-printable characters without C-style
419 backslash sequences use a three digit octal sequence.
421 Use URI encoding as described in RFC 1738.
426 represents a lower case hexadecimal digit.
428 Use MIME Quoted-Printable encoding as described in RFC 2045, only don't
429 break lines and don't handle CRLF.
434 represents an upper case hexadecimal digit.
437 There is one additional flag,
440 doubling of backslashes and the backslash before the default
441 format (that is, control characters are represented by
446 With this flag set, the encoding is
447 ambiguous and non-invertible.
448 .Sh MULTIBYTE CHARACTER SUPPORT
449 These functions support multibyte character input.
450 The encoding conversion is influenced by the setting of the
452 environment variable which defines the set of characters
453 that can be copied without encoding.
457 is set, processing is done assuming the C locale and overriding
458 any other environment settings.
460 When 8-bit data is present in the input,
462 must be set to the correct locale or to the C locale.
463 If the locales of the data and the conversion are mismatched,
464 multibyte character recognition may fail and encoding will be performed
465 byte-by-byte instead.
469 must be four times the number of bytes processed from
471 But note that each multibyte character can be up to
475 .\" .Xr multibyte 3 )
476 so in terms of multibyte characters,
480 times the number of characters processed from
483 .Bl -tag -width ".Ev LC_CTYPE"
485 Specify the locale of the input data.
486 Set to C if the input data locale is unknown.
501 will return \-1 when the
503 destination buffer size is not enough to perform the conversion while
507 .Bl -tag -width ".Bq Er ENOSPC"
509 The destination buffer size is not large enough to perform the conversion.
515 .\" .Xr multibyte 3 ,
519 .%T Uniform Resource Locators (URL)
523 .%T "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies"
532 functions first appeared in
539 functions appeared in
541 The buffer size limited versions of the functions
553 Multibyte character support was added in