1.\" $NetBSD: vis.3,v 1.50 2022/12/04 11:25:08 uwe Exp $ 2.\" 3.\" Copyright (c) 1989, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)vis.3 8.1 (Berkeley) 6/9/93 31.\" 32.Dd April 22, 2017 33.Dt VIS 3 34.Os 35.Sh NAME 36.Nm vis , 37.Nm nvis , 38.Nm strvis , 39.Nm stravis , 40.Nm strnvis , 41.Nm strvisx , 42.Nm strnvisx , 43.Nm strenvisx , 44.Nm svis , 45.Nm snvis , 46.Nm strsvis , 47.Nm strsnvis , 48.Nm strsvisx , 49.Nm strsnvisx , 50.Nm strsenvisx 51.Nd visually encode characters 52.Sh LIBRARY 53.Lb libc 54.Sh SYNOPSIS 55.In vis.h 56.Ft char * 57.Fn vis "char *dst" "int c" "int flag" "int nextc" 58.Ft char * 59.Fn nvis "char *dst" "size_t dlen" "int c" "int flag" "int nextc" 60.Ft int 61.Fn strvis "char *dst" "const char *src" "int flag" 62.Ft int 63.Fn stravis "char **dst" "const char *src" "int flag" 64.Ft int 65.Fn strnvis "char *dst" "size_t dlen" "const char *src" "int flag" 66.Ft int 67.Fn strvisx "char *dst" "const char *src" "size_t len" "int flag" 68.Ft int 69.Fn strnvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" 70.Ft int 71.Fn strenvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" "int *cerr_ptr" 72.Ft char * 73.Fn svis "char *dst" "int c" "int flag" "int nextc" "const char *extra" 74.Ft char * 75.Fn snvis "char *dst" "size_t dlen" "int c" "int flag" "int nextc" "const char *extra" 76.Ft int 77.Fn strsvis "char *dst" "const char *src" "int flag" "const char *extra" 78.Ft int 79.Fn strsnvis "char *dst" "size_t dlen" "const char *src" "int flag" "const char *extra" 80.Ft int 81.Fn strsvisx "char *dst" "const char *src" "size_t len" "int flag" "const char *extra" 82.Ft int 83.Fn strsnvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" "const char *extra" 84.Ft int 85.Fn strsenvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" "const char *extra" "int *cerr_ptr" 86.Sh DESCRIPTION 87The 88.Fn vis 89function 90copies into 91.Fa dst 92a string which represents the character 93.Fa c . 94If 95.Fa c 96needs no encoding, it is copied in unaltered. 97The string is null terminated, and a pointer to the end of the string is 98returned. 99The maximum length of any encoding is four 100bytes (not including the trailing 101.Dv NUL ) ; 102thus, when 103encoding a set of characters into a buffer, the size of the buffer should 104be four times the number of bytes encoded, plus one for the trailing 105.Dv NUL . 106The flag parameter is used for altering the default range of 107characters considered for encoding and for altering the visual 108representation. 109The additional character, 110.Fa nextc , 111is only used when selecting the 112.Dv VIS_CSTYLE 113encoding format (explained below). 114.Pp 115The 116.Fn strvis , 117.Fn stravis , 118.Fn strnvis , 119.Fn strvisx , 120and 121.Fn strnvisx 122functions copy into 123.Fa dst 124a visual representation of 125the string 126.Fa src . 127The 128.Fn strvis 129and 130.Fn strnvis 131functions encode characters from 132.Fa src 133up to the 134first 135.Dv NUL . 136The 137.Fn strvisx 138and 139.Fn strnvisx 140functions encode exactly 141.Fa len 142characters from 143.Fa src 144(this 145is useful for encoding a block of data that may contain 146.Dv NUL Ns 's ) . 147Both forms 148.Dv NUL 149terminate 150.Fa dst . 151The size of 152.Fa dst 153must be four times the number 154of bytes encoded from 155.Fa src 156(plus one for the 157.Dv NUL ) . 158Both 159forms return the number of characters in 160.Fa dst 161(not including the trailing 162.Dv NUL ) . 163The 164.Fn stravis 165function allocates space dynamically to hold the string. 166The 167.Dq Nm n 168versions of the functions also take an additional argument 169.Fa dlen 170that indicates the length of the 171.Fa dst 172buffer. 173If 174.Fa dlen 175is not large enough to fit the converted string then the 176.Fn strnvis 177and 178.Fn strnvisx 179functions return \-1 and set 180.Va errno 181to 182.Er ENOSPC . 183The 184.Fn strenvisx 185function takes an additional argument, 186.Fa cerr_ptr , 187that is used to pass in and out a multibyte conversion error flag. 188This is useful when processing single characters at a time when 189it is possible that the locale may be set to something other 190than the locale of the characters in the input data. 191.Pp 192The functions 193.Fn svis , 194.Fn snvis , 195.Fn strsvis , 196.Fn strsnvis , 197.Fn strsvisx , 198.Fn strsnvisx , 199and 200.Fn strsenvisx 201correspond to 202.Fn vis , 203.Fn nvis , 204.Fn strvis , 205.Fn strnvis , 206.Fn strvisx , 207.Fn strnvisx , 208and 209.Fn strenvisx 210but have an additional argument 211.Fa extra , 212pointing to a 213.Dv NUL 214terminated list of characters. 215These characters will be copied encoded or backslash-escaped into 216.Fa dst . 217These functions are useful e.g. to remove the special meaning 218of certain characters to shells. 219.Pp 220The encoding is a unique, invertible representation composed entirely of 221graphic characters; it can be decoded back into the original form using 222the 223.Xr unvis 3 , 224.Xr strunvis 3 225or 226.Xr strnunvis 3 227functions. 228.Pp 229There are two parameters that can be controlled: the range of 230characters that are encoded (applies only to 231.Fn vis , 232.Fn nvis , 233.Fn strvis , 234.Fn strnvis , 235.Fn strvisx , 236and 237.Fn strnvisx ) , 238and the type of representation used. 239By default, all non-graphic characters, 240except space, tab, and newline are encoded (see 241.Xr isgraph 3 ) . 242The following flags 243alter this: 244.Bl -tag -width VIS_WHITEX 245.It Dv VIS_DQ 246Also encode double quotes 247.It Dv VIS_GLOB 248Also encode the magic characters 249.Ql ( * , 250.Ql \&? , 251.Ql \&[ , 252and 253.Ql # ) 254recognized by 255.Xr glob 3 . 256.It Dv VIS_SHELL 257Also encode the meta characters used by shells (in addition to the glob 258characters): 259.Ql ( ' , 260.Ql ` , 261.Ql \&" , 262.Ql \&; , 263.Ql & , 264.Ql < , 265.Ql > , 266.Ql \&( , 267.Ql \&) , 268.Ql \&| , 269.Ql \&] , 270.Ql \e , 271.Ql $ , 272.Ql \&! , 273.Ql \&^ , 274and 275.Ql ~ ) . 276.It Dv VIS_SP 277Also encode space. 278.It Dv VIS_TAB 279Also encode tab. 280.It Dv VIS_NL 281Also encode newline. 282.It Dv VIS_WHITE 283Synonym for 284.Dv VIS_SP | VIS_TAB | VIS_NL . 285.It Dv VIS_META 286Synonym for 287.Dv VIS_WHITE | VIS_GLOB | VIS_SHELL . 288.It Dv VIS_SAFE 289Only encode 290.Dq unsafe 291characters. 292Unsafe means control characters which may cause common terminals to perform 293unexpected functions. 294Currently this form allows space, tab, newline, backspace, bell, and 295return \(em in addition to all graphic characters \(em unencoded. 296.El 297.Pp 298(The above flags have no effect for 299.Fn svis , 300.Fn snvis , 301.Fn strsvis , 302.Fn strsnvis , 303.Fn strsvisx , 304and 305.Fn strsnvisx . 306When using these functions, place all graphic characters to be 307encoded in an array pointed to by 308.Fa extra . 309In general, the backslash character should be included in this array, see the 310warning on the use of the 311.Dv VIS_NOSLASH 312flag below). 313.Pp 314There are six forms of encoding. 315All forms use the backslash character 316.Ql \e 317to introduce a special 318sequence; two backslashes are used to represent a real backslash, 319except 320.Dv VIS_HTTPSTYLE 321that uses 322.Ql % , 323or 324.Dv VIS_MIMESTYLE 325that uses 326.Ql = . 327These are the visual formats: 328.Bl -tag -width VIS_CSTYLE 329.It (default) 330Use an 331.Ql M 332to represent meta characters (characters with the 8th 333bit set), and use caret 334.Ql ^ 335to represent control characters (see 336.Xr iscntrl 3 ) . 337The following formats are used: 338.Bl -tag -width xxxxx 339.It Dv \e^C 340Represents the control character 341.Ql C . 342Spans characters 343.Ql \e000 344through 345.Ql \e037 , 346and 347.Ql \e177 348(as 349.Ql \e^? ) . 350.It Dv \eM-C 351Represents character 352.Ql C 353with the 8th bit set. 354Spans characters 355.Ql \e241 356through 357.Ql \e376 . 358.It Dv \eM^C 359Represents control character 360.Ql C 361with the 8th bit set. 362Spans characters 363.Ql \e200 364through 365.Ql \e237 , 366and 367.Ql \e377 368(as 369.Ql \eM^? ) . 370.It Dv \e040 371Represents 372.Tn ASCII 373space. 374.It Dv \e240 375Represents Meta-space. 376.El 377.It Dv VIS_CSTYLE 378Use C-style backslash sequences to represent standard non-printable 379characters. 380The 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) 391.Ed 392.Pp 393When using this format, the 394.Fa nextc 395parameter is looked at to determine if a 396.Dv NUL 397character can be encoded as 398.Ql \e0 399instead of 400.Ql \e000 . 401If 402.Fa nextc 403is an octal digit, the latter representation is used to 404avoid ambiguity. 405.Pp 406Non-printable characters without C-style 407backslash sequences use the default representation. 408.It Dv VIS_OCTAL 409Use a three digit octal sequence. 410The form is 411.Ql \eddd 412where 413.Em d 414represents an octal digit. 415.It Dv VIS_CSTYLE \&| Dv VIS_OCTAL 416Same as 417.Dv VIS_CSTYLE 418except that non-printable characters without C-style 419backslash sequences use a three digit octal sequence. 420.It Dv VIS_HTTPSTYLE 421Use URI encoding as described in RFC 1738. 422The form is 423.Ql %xx 424where 425.Em x 426represents a lower case hexadecimal digit. 427.It Dv VIS_MIMESTYLE 428Use MIME Quoted-Printable encoding as described in RFC 2045, only don't 429break lines and don't handle CRLF. 430The form is 431.Ql =XX 432where 433.Em X 434represents an upper case hexadecimal digit. 435.El 436.Pp 437There is one additional flag, 438.Dv VIS_NOSLASH , 439which inhibits the 440doubling of backslashes and the backslash before the default 441format (that is, control characters are represented by 442.Ql ^C 443and 444meta characters as 445.Ql M-C ) . 446With this flag set, the encoding is 447ambiguous and non-invertible. 448.Sh MULTIBYTE CHARACTER SUPPORT 449These functions support multibyte character input. 450The encoding conversion is influenced by the setting of the 451.Ev LC_CTYPE 452environment variable which defines the set of characters 453that can be copied without encoding. 454.Pp 455If 456.Dv VIS_NOLOCALE 457is set, processing is done assuming the C locale and overriding 458any other environment settings. 459.Pp 460When 8-bit data is present in the input, 461.Ev LC_CTYPE 462must be set to the correct locale or to the C locale. 463If the locales of the data and the conversion are mismatched, 464multibyte character recognition may fail and encoding will be performed 465byte-by-byte instead. 466.Pp 467As noted above, 468.Fa dst 469must be four times the number of bytes processed from 470.Fa src . 471But note that each multibyte character can be up to 472.Dv MB_LEN_MAX 473bytes 474.\" (see 475.\" .Xr multibyte 3 ) 476so in terms of multibyte characters, 477.Fa dst 478must be four times 479.Dv MB_LEN_MAX 480times the number of characters processed from 481.Fa src . 482.Sh ENVIRONMENT 483.Bl -tag -width ".Ev LC_CTYPE" 484.It Ev LC_CTYPE 485Specify the locale of the input data. 486Set to C if the input data locale is unknown. 487.El 488.Sh ERRORS 489The functions 490.Fn nvis 491and 492.Fn snvis 493will return 494.Dv NULL 495and the functions 496.Fn strnvis , 497.Fn strnvisx , 498.Fn strsnvis , 499and 500.Fn strsnvisx , 501will return \-1 when the 502.Fa dlen 503destination buffer size is not enough to perform the conversion while 504setting 505.Va errno 506to: 507.Bl -tag -width ".Bq Er ENOSPC" 508.It Bq Er ENOSPC 509The destination buffer size is not large enough to perform the conversion. 510.El 511.Sh SEE ALSO 512.Xr unvis 1 , 513.Xr vis 1 , 514.Xr glob 3 , 515.\" .Xr multibyte 3 , 516.Xr unvis 3 517.Rs 518.%A T. Berners-Lee 519.%T Uniform Resource Locators (URL) 520.%O "RFC 1738" 521.Re 522.Rs 523.%T "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies" 524.%O "RFC 2045" 525.Re 526.Sh HISTORY 527The 528.Fn vis , 529.Fn strvis , 530and 531.Fn strvisx 532functions first appeared in 533.Bx 4.4 . 534The 535.Fn svis , 536.Fn strsvis , 537and 538.Fn strsvisx 539functions appeared in 540.Nx 1.5 541and 542.Fx 9.2 . 543The buffer size limited versions of the functions 544.Po Fn nvis , 545.Fn strnvis , 546.Fn strnvisx , 547.Fn snvis , 548.Fn strsnvis , 549and 550.Fn strsnvisx Pc 551appeared in 552.Nx 6.0 553and 554.Fx 9.2 . 555Multibyte character support was added in 556.Nx 7.0 557and 558.Fx 9.2 . 559