1 2[//000000001]: # (uri \- Tcl Uniform Resource Identifier Management) 3[//000000002]: # (Generated from file 'uri\.man' by tcllib/doctools with format 'markdown') 4[//000000003]: # (uri\(n\) 1\.2\.7 tcllib "Tcl Uniform Resource Identifier Management") 5 6<hr> [ <a href="../../../../toc.md">Main Table Of Contents</a> | <a 7href="../../../toc.md">Table Of Contents</a> | <a 8href="../../../../index.md">Keyword Index</a> | <a 9href="../../../../toc0.md">Categories</a> | <a 10href="../../../../toc1.md">Modules</a> | <a 11href="../../../../toc2.md">Applications</a> ] <hr> 12 13# NAME 14 15uri \- URI utilities 16 17# <a name='toc'></a>Table Of Contents 18 19 - [Table Of Contents](#toc) 20 21 - [Synopsis](#synopsis) 22 23 - [Description](#section1) 24 25 - [COMMANDS](#section2) 26 27 - [SCHEMES](#section3) 28 29 - [EXTENDING](#section4) 30 31 - [QUIRK OPTIONS](#section5) 32 33 - [BACKWARD COMPATIBILITY](#subsection1) 34 35 - [NEW DESIGNS](#subsection2) 36 37 - [DEFAULT VALUES](#subsection3) 38 39 - [EXAMPLES](#section6) 40 41 - [CREDITS](#section7) 42 43 - [Bugs, Ideas, Feedback](#section8) 44 45 - [Keywords](#keywords) 46 47 - [Category](#category) 48 49# <a name='synopsis'></a>SYNOPSIS 50 51package require Tcl 8\.2 52package require uri ?1\.2\.7? 53 54[__uri::setQuirkOption__ *option* ?*value*?](#1) 55[__uri::split__ *url* ?*defaultscheme*?](#2) 56[__uri::join__ ?*key* *value*?\.\.\.](#3) 57[__uri::resolve__ *base* *url*](#4) 58[__uri::isrelative__ *url*](#5) 59[__uri::geturl__ *url* ?*options*\.\.\.?](#6) 60[__uri::canonicalize__ *uri*](#7) 61[__uri::register__ *schemeList* *script*](#8) 62 63# <a name='description'></a>DESCRIPTION 64 65This package does two things\. 66 67First, it provides a number of commands for manipulating URLs/URIs and fetching 68data specified by them\. For fetching data this package analyses the requested 69URL/URI and then dispatches it to the appropriate package 70\(__[http](\.\./\.\./\.\./\.\./index\.md\#http)__, 71__[ftp](\.\./ftp/ftp\.md)__, \.\.\.\) for actual retrieval\. Currently these 72commands are defined for the schemes *[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 73*[https](\.\./\.\./\.\./\.\./index\.md\#https)*, 74*[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*, 75*[mailto](\.\./\.\./\.\./\.\./index\.md\#mailto)*, 76*[news](\.\./\.\./\.\./\.\./index\.md\#news)*, 77*[ldap](\.\./\.\./\.\./\.\./index\.md\#ldap)*, *ldaps* and 78*[file](\.\./\.\./\.\./\.\./index\.md\#file)*\. The package __uri::urn__ adds 79scheme *[urn](\.\./\.\./\.\./\.\./index\.md\#urn)*\. 80 81Second, it provides regular expressions for a number of __registered__ 82URL/URI schemes\. Registered schemes are currently 83*[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*, 84*[ldap](\.\./\.\./\.\./\.\./index\.md\#ldap)*, *ldaps*, 85*[file](\.\./\.\./\.\./\.\./index\.md\#file)*, 86*[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 87*[https](\.\./\.\./\.\./\.\./index\.md\#https)*, 88*[gopher](\.\./\.\./\.\./\.\./index\.md\#gopher)*, 89*[mailto](\.\./\.\./\.\./\.\./index\.md\#mailto)*, 90*[news](\.\./\.\./\.\./\.\./index\.md\#news)*, 91*[wais](\.\./\.\./\.\./\.\./index\.md\#wais)* and 92*[prospero](\.\./\.\./\.\./\.\./index\.md\#prospero)*\. The package __uri::urn__ 93adds scheme *[urn](\.\./\.\./\.\./\.\./index\.md\#urn)*\. 94 95The commands of the package conform to RFC 3986 96\([https://www\.rfc\-editor\.org/rfc/rfc3986\.txt](https://www\.rfc\-editor\.org/rfc/rfc3986\.txt)\), 97with the exception of a loophole arising from RFC 1630 and described in RFC 3986 98Sections 5\.2\.2 and 5\.4\.2\. The loophole allows a relative URI to include a scheme 99if it is the same as the scheme of the base URI against which it is resolved\. 100RFC 3986 recommends avoiding this usage\. 101 102# <a name='section2'></a>COMMANDS 103 104 - <a name='1'></a>__uri::setQuirkOption__ *option* ?*value*? 105 106 __uri::setQuirkOption__ is an accessor command for a number of "quirk 107 options"\. The command has the same semantics as the command 108 __[set](\.\./\.\./\.\./\.\./index\.md\#set)__: when called with one argument 109 it reads an existing value; with two arguments it writes a new value\. The 110 value of a "quirk option" is boolean: the value __false__ requests 111 conformance with RFC 3986, while __true__ requests use of the quirk\. See 112 section [QUIRK OPTIONS](#section5) for discussion of the different 113 options and their purpose\. 114 115 - <a name='2'></a>__uri::split__ *url* ?*defaultscheme*? 116 117 __uri::split__ takes a *url*, decodes it and then returns a list of 118 key/value pairs suitable for __array set__ containing the constituents 119 of the *url*\. If the scheme is missing from the *url* it defaults to the 120 value of *defaultscheme* if it was specified, or 121 *[http](\.\./\.\./\.\./\.\./index\.md\#http)* else\. Currently the schemes 122 *[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 123 *[https](\.\./\.\./\.\./\.\./index\.md\#https)*, 124 *[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*, 125 *[mailto](\.\./\.\./\.\./\.\./index\.md\#mailto)*, 126 *[news](\.\./\.\./\.\./\.\./index\.md\#news)*, 127 *[ldap](\.\./\.\./\.\./\.\./index\.md\#ldap)*, *ldaps* and 128 *[file](\.\./\.\./\.\./\.\./index\.md\#file)* are supported by the package 129 itself\. See section [EXTENDING](#section4) on how to expand that range\. 130 131 The set of constituents of a URL \(= the set of keys in the returned 132 dictionary\) is dependent on the scheme of the URL\. The only key which is 133 therefore always present is __scheme__\. For the following schemes the 134 constituents and their keys are known: 135 136 * ftp 137 138 __user__, __pwd__, __host__, __port__, __path__, 139 __type__, __pbare__\. The pbare is optional\. 140 141 * http\(s\) 142 143 __user__, __pwd__, __host__, __port__, __path__, 144 __query__, __fragment__, __pbare__\. The pbare is optional\. 145 146 * file 147 148 __path__, __host__\. The host is optional\. 149 150 * mailto 151 152 __user__, __host__\. The host is optional\. 153 154 * ldap\(s\) 155 156 __host__, __port__, __dn__, __attrs__, __scope__, 157 __filter__, __extensions__ 158 159 * news 160 161 Either __message\-id__ or __newsgroup\-name__\. 162 163 For discussion of the boolean __pbare__ see options *NoInitialSlash* 164 and *NoExtraKeys* in [QUIRK OPTIONS](#section5)\. 165 166 The constituents are returned as slices of the argument *url*, without 167 removal of percent\-encoding \("url\-encoding"\) or other adaptations\. Notably, 168 on Windows® the __path__ in scheme 169 *[file](\.\./\.\./\.\./\.\./index\.md\#file)* is not a valid local filename\. See 170 [EXAMPLES](#section6) for more information\. 171 172 - <a name='3'></a>__uri::join__ ?*key* *value*?\.\.\. 173 174 __uri::join__ takes a list of key/value pairs \(generated by 175 __uri::split__, for example\) and returns the canonical URL they 176 represent\. Currently the schemes *[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 177 *[https](\.\./\.\./\.\./\.\./index\.md\#https)*, 178 *[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*, 179 *[mailto](\.\./\.\./\.\./\.\./index\.md\#mailto)*, 180 *[news](\.\./\.\./\.\./\.\./index\.md\#news)*, 181 *[ldap](\.\./\.\./\.\./\.\./index\.md\#ldap)*, *ldaps* and 182 *[file](\.\./\.\./\.\./\.\./index\.md\#file)* are supported by the package 183 itself\. See section [EXTENDING](#section4) on how to expand that range\. 184 185 The arguments are expected to be slices of a valid URL, with 186 percent\-encoding \("url\-encoding"\) and any other necessary adaptations\. 187 Notably, on Windows the __path__ in scheme 188 *[file](\.\./\.\./\.\./\.\./index\.md\#file)* is not a valid local filename\. See 189 [EXAMPLES](#section6) for more information\. 190 191 - <a name='4'></a>__uri::resolve__ *base* *url* 192 193 __uri::resolve__ resolves the specified *url* relative to *base*, in 194 conformance with RFC 3986\. In other words: a non\-relative *url* is 195 returned unchanged, whereas for a relative *url* the missing parts are 196 taken from *base* and prepended to it\. The result of this operation is 197 returned\. For an empty *url* the result is *base*, without its URI 198 fragment \(if any\)\. The command is available for schemes 199 *[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 200 *[https](\.\./\.\./\.\./\.\./index\.md\#https)*, 201 *[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*, and 202 *[file](\.\./\.\./\.\./\.\./index\.md\#file)*\. 203 204 - <a name='5'></a>__uri::isrelative__ *url* 205 206 __uri::isrelative__ determines whether the specified *url* is absolute 207 or relative\. The command is available for a *url* of any scheme\. 208 209 - <a name='6'></a>__uri::geturl__ *url* ?*options*\.\.\.? 210 211 __uri::geturl__ decodes the specified *url* and then dispatches the 212 request to the package appropriate for the scheme found in the URL\. The 213 command assumes that the package to handle the given scheme either has the 214 same name as the scheme itself \(including possible capitalization\) followed 215 by __::geturl__, or, in case of this failing, has the same name as the 216 scheme itself \(including possible capitalization\)\. It further assumes that 217 whatever package was loaded provides a __geturl__\-command in the 218 namespace of the same name as the package itself\. This command is called 219 with the given *url* and all given *options*\. Currently __geturl__ 220 does not handle any options itself\. 221 222 *Note:* *[file](\.\./\.\./\.\./\.\./index\.md\#file)*\-URLs are an exception to 223 the rule described above\. They are handled internally\. 224 225 It is not possible to specify results of the command\. They depend on the 226 __geturl__\-command for the scheme the request was dispatched to\. 227 228 - <a name='7'></a>__uri::canonicalize__ *uri* 229 230 __uri::canonicalize__ returns the canonical form of a URI\. The canonical 231 form of a URI is one where relative path specifications, i\.e\. "\." and "\.\.", 232 have been resolved\. The command is available for all URI schemes that have 233 __uri::split__ and __uri::join__ commands\. The command returns a 234 canonicalized URI if the URI scheme has a __path__ component \(i\.e\. 235 *[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 236 *[https](\.\./\.\./\.\./\.\./index\.md\#https)*, 237 *[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*, and 238 *[file](\.\./\.\./\.\./\.\./index\.md\#file)*\)\. For schemes that have 239 __uri::split__ and __uri::join__ commands but no __path__ 240 component \(i\.e\. *[mailto](\.\./\.\./\.\./\.\./index\.md\#mailto)*, 241 *[news](\.\./\.\./\.\./\.\./index\.md\#news)*, 242 *[ldap](\.\./\.\./\.\./\.\./index\.md\#ldap)*, and *ldaps*\), the command 243 returns the *uri* unchanged\. 244 245 - <a name='8'></a>__uri::register__ *schemeList* *script* 246 247 __uri::register__ registers the first element of *schemeList* as a new 248 scheme and the remaining elements as aliases for this scheme\. It creates the 249 namespace for the scheme and executes the *script* in the new namespace\. 250 The script has to declare variables containing regular expressions relevant 251 to the scheme\. At least the variable __schemepart__ has to be declared 252 as that one is used to extend the variables keeping track of the registered 253 schemes\. 254 255# <a name='section3'></a>SCHEMES 256 257In addition to the commands mentioned above this package provides regular 258expression to recognize URLs for a number of URL schemes\. 259 260For each supported scheme a namespace of the same name as the scheme itself is 261provided inside of the namespace *uri* containing the variable __url__ 262whose contents are a regular expression to recognize URLs of that scheme\. 263Additional variables may contain regular expressions for parts of URLs for that 264scheme\. 265 266The variable __uri::schemes__ contains a list of all registered schemes\. 267Currently these are *[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*, 268*[ldap](\.\./\.\./\.\./\.\./index\.md\#ldap)*, *ldaps*, 269*[file](\.\./\.\./\.\./\.\./index\.md\#file)*, 270*[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 271*[https](\.\./\.\./\.\./\.\./index\.md\#https)*, 272*[gopher](\.\./\.\./\.\./\.\./index\.md\#gopher)*, 273*[mailto](\.\./\.\./\.\./\.\./index\.md\#mailto)*, 274*[news](\.\./\.\./\.\./\.\./index\.md\#news)*, 275*[wais](\.\./\.\./\.\./\.\./index\.md\#wais)* and 276*[prospero](\.\./\.\./\.\./\.\./index\.md\#prospero)*\. 277 278# <a name='section4'></a>EXTENDING 279 280Extending the range of schemes supported by __uri::split__ and 281__uri::join__ is easy because both commands do not handle the request by 282themselves but dispatch it to another command in the *uri* namespace using the 283scheme of the URL as criterion\. 284 285__uri::split__ and __uri::join__ call __Split\[string totitle 286<scheme>\]__ and __Join\[string totitle <scheme>\]__ respectively\. 287 288The provision of split and join commands is sufficient to extend the commands 289__uri::canonicalize__ and __uri::geturl__ \(the latter subject to the 290availability of a suitable package with a __geturl__ command\)\. In contrast, 291to extend the command __uri::resolve__ to a new scheme, the command itself 292must be modified\. 293 294To extend the range of schemes for which pattern information is available, use 295the command __uri::register__\. 296 297An example of a package that provides both commands and pattern information for 298a new scheme is __uri::urn__, which adds scheme 299*[urn](\.\./\.\./\.\./\.\./index\.md\#urn)*\. 300 301# <a name='section5'></a>QUIRK OPTIONS 302 303The value of a "quirk option" is boolean: the value __false__ requests 304conformance with RFC 3986, while __true__ requests use of the quirk\. Use 305command __uri::setQuirkOption__ to access the values of quirk options\. 306 307Quirk options are useful both for allowing backwards compatibility when a 308command specification changes, and for adding useful features that are not 309included in RFC specifications\. The following quirk options are currently 310defined: 311 312 - *NoInitialSlash* 313 314 This quirk option concerns the leading character of __path__ \(if 315 non\-empty\) in the schemes *[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 316 *[https](\.\./\.\./\.\./\.\./index\.md\#https)*, and 317 *[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*\. 318 319 RFC 3986 defines __path__ in an absolute URI to have an initial "/", 320 unless the value of __path__ is the empty string\. For the scheme 321 *[file](\.\./\.\./\.\./\.\./index\.md\#file)*, all versions of package 322 __uri__ follow this rule\. The quirk option *NoInitialSlash* does not 323 apply to scheme *[file](\.\./\.\./\.\./\.\./index\.md\#file)*\. 324 325 For the schemes *[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 326 *[https](\.\./\.\./\.\./\.\./index\.md\#https)*, and 327 *[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*, versions of __uri__ before 328 1\.2\.7 define the __path__ *NOT* to include an initial "/"\. When the 329 quirk option *NoInitialSlash* is __true__ \(the default\), this behavior 330 is also used in version 1\.2\.7\. To use instead values of __path__ as 331 defined by RFC 3986, set this quirk option to __false__\. 332 333 This setting does not affect RFC 3986 conformance\. If *NoInitialSlash* is 334 __true__, then the value of __path__ in the schemes 335 *[http](\.\./\.\./\.\./\.\./index\.md\#http)*, 336 *[https](\.\./\.\./\.\./\.\./index\.md\#https)*, or 337 *[ftp](\.\./\.\./\.\./\.\./index\.md\#ftp)*, cannot distinguish between URIs in 338 which the full "RFC 3986 path" is the empty string "" or a single slash "/" 339 respectively\. The missing information is recorded in an additional 340 __uri::split__ key __pbare__\. 341 342 The boolean __pbare__ is defined when quirk options *NoInitialSlash* 343 and *NoExtraKeys* have values __true__ and __false__ respectively\. 344 In this case, if the value of __path__ is the empty string "", 345 __pbare__ is __true__ if the full "RFC 3986 path" is "", and 346 __pbare__ is __false__ if the full "RFC 3986 path" is "/"\. 347 348 Using this quirk option *NoInitialSlash* is a matter of preference\. 349 350 - *NoExtraKeys* 351 352 This quirk option permits full backward compatibility with versions of 353 __uri__ before 1\.2\.7, by omitting the __uri::split__ key 354 __pbare__ described above \(see quirk option *NoInitialSlash*\)\. The 355 outcome is greater backward compatibility of the __uri::split__ command, 356 but an inability to distinguish between URIs in which the full "RFC 3986 357 path" is the empty string "" or a single slash "/" respectively \- i\.e\. a 358 minor non\-conformance with RFC 3986\. 359 360 If the quirk option *NoExtraKeys* is __false__ \(the default\), command 361 __uri::split__ returns an additional key __pbare__, and the commands 362 comply with RFC 3986\. If the quirk option *NoExtraKeys* is __true__, 363 the key __pbare__ is not defined and there is not full conformance with 364 RFC 3986\. 365 366 Using the quirk option *NoExtraKeys* is *NOT* recommended, because if 367 set to __true__ it will reduce conformance with RFC 3986\. The option is 368 included only for compatibility with code, written for earlier versions of 369 __uri__, that needs values of __path__ without a leading "/", *AND 370 ALSO* cannot tolerate unexpected keys in the results of __uri::split__\. 371 372 - *HostAsDriveLetter* 373 374 When handling the scheme *[file](\.\./\.\./\.\./\.\./index\.md\#file)* on the 375 Windows platform, versions of __uri__ before 1\.2\.7 use the __host__ 376 field to represent a Windows drive letter and the colon that follows it, and 377 the __path__ field to represent the filename path after the colon\. Such 378 URIs are invalid, and are not recognized by any RFC\. When the quirk option 379 *HostAsDriveLetter* is __true__, this behavior is also used in version 380 1\.2\.7\. To use *[file](\.\./\.\./\.\./\.\./index\.md\#file)* URIs on Windows that 381 conform to RFC 3986, set this quirk option to __false__ \(the default\)\. 382 383 Using this quirk is *NOT* recommended, because if set to __true__ it 384 will cause the __uri__ commands to expect and produce invalid URIs\. The 385 option is included only for compatibility with legacy code\. 386 387 - *RemoveDoubleSlashes* 388 389 When a URI is canonicalized by __uri::canonicalize__, its __path__ 390 is normalized by removal of segments "\." and "\.\."\. RFC 3986 does not mandate 391 the removal of empty segments "" \(i\.e\. the merger of double slashes, which 392 is a feature of filename normalization but not of URI __path__ 393 normalization\): it treats URIs with excess slashes as referring to different 394 resources\. When the quirk option *RemoveDoubleSlashes* is __true__ 395 \(the default\), empty segments will be removed from __path__\. To prevent 396 removal, and thereby conform to RFC 3986, set this quirk option to 397 __false__\. 398 399 Using this quirk is a matter of preference\. A URI with double slashes in its 400 path was most likely generated by error, certainly so if it has a 401 straightforward mapping to a file on a server\. In some cases it may be 402 better to sanitize the URI; in others, to keep the URI and let the server 403 handle the possible error\. 404 405## <a name='subsection1'></a>BACKWARD COMPATIBILITY 406 407To behave as similarly as possible to versions of __uri__ earlier than 4081\.2\.7, set the following quirk options: 409 410 - __uri::setQuirkOption__ *NoInitialSlash* 1 411 412 - __uri::setQuirkOption__ *NoExtraKeys* 1 413 414 - __uri::setQuirkOption__ *HostAsDriveLetter* 1 415 416 - __uri::setQuirkOption__ *RemoveDoubleSlashes* 0 417 418In code that can tolerate the return by __uri::split__ of an additional key 419__pbare__, set 420 421 - __uri::setQuirkOption__ *NoExtraKeys* 0 422 423in order to achieve greater compliance with RFC 3986\. 424 425## <a name='subsection2'></a>NEW DESIGNS 426 427For new projects, the following settings are recommended: 428 429 - __uri::setQuirkOption__ *NoInitialSlash* 0 430 431 - __uri::setQuirkOption__ *NoExtraKeys* 0 432 433 - __uri::setQuirkOption__ *HostAsDriveLetter* 0 434 435 - __uri::setQuirkOption__ *RemoveDoubleSlashes* 0|1 436 437## <a name='subsection3'></a>DEFAULT VALUES 438 439The default values for package __uri__ version 1\.2\.7 are intended to be a 440compromise between backwards compatibility and improved features\. Different 441default values may be chosen in future versions of package __uri__\. 442 443 - __uri::setQuirkOption__ *NoInitialSlash* 1 444 445 - __uri::setQuirkOption__ *NoExtraKeys* 0 446 447 - __uri::setQuirkOption__ *HostAsDriveLetter* 0 448 449 - __uri::setQuirkOption__ *RemoveDoubleSlashes* 1 450 451# <a name='section6'></a>EXAMPLES 452 453A Windows® local filename such as "__C:\\Other Files\\startup\.txt__" is not 454suitable for use as the __path__ element of a URI in the scheme 455*[file](\.\./\.\./\.\./\.\./index\.md\#file)*\. 456 457The Tcl command __file normalize__ will convert the backslashes to forward 458slashes\. To generate a valid __path__ for the scheme 459*[file](\.\./\.\./\.\./\.\./index\.md\#file)*, the normalized filename must be 460prepended with "__/__", and then any characters that do not match the 461__regexp__ bracket expression 462 463 [a-zA-Z0-9$_.+!*'(,)?:@&=-] 464 465must be percent\-encoded\. 466 467The result in this example is "__/C:/Other%20Files/startup\.txt__" which is a 468valid value for __path__\. 469 470 % uri::join path /C:/Other%20Files/startup.txt scheme file 471 472 file:///C:/Other%20Files/startup.txt 473 474 % uri::split file:///C:/Other%20Files/startup.txt 475 476 path /C:/Other%20Files/startup.txt scheme file 477 478On UNIX® systems filenames begin with "__/__" which is also used as the 479directory separator\. The only action needed to convert a filename to a valid 480__path__ is percent\-encoding\. 481 482# <a name='section7'></a>CREDITS 483 484Original code \(regular expressions\) by Andreas Kupries\. Modularisation by Steve 485Ball, also the split/join/resolve functionality\. RFC 3986 conformance by Keith 486Nash\. 487 488# <a name='section8'></a>Bugs, Ideas, Feedback 489 490This document, and the package it describes, will undoubtedly contain bugs and 491other problems\. Please report such in the category *uri* of the [Tcllib 492Trackers](http://core\.tcl\.tk/tcllib/reportlist)\. Please also report any ideas 493for enhancements you may have for either package and/or documentation\. 494 495When proposing code changes, please provide *unified diffs*, i\.e the output of 496__diff \-u__\. 497 498Note further that *attachments* are strongly preferred over inlined patches\. 499Attachments can be made by going to the __Edit__ form of the ticket 500immediately after its creation, and then using the left\-most button in the 501secondary navigation bar\. 502 503# <a name='keywords'></a>KEYWORDS 504 505[fetching information](\.\./\.\./\.\./\.\./index\.md\#fetching\_information), 506[file](\.\./\.\./\.\./\.\./index\.md\#file), [ftp](\.\./\.\./\.\./\.\./index\.md\#ftp), 507[gopher](\.\./\.\./\.\./\.\./index\.md\#gopher), 508[http](\.\./\.\./\.\./\.\./index\.md\#http), [https](\.\./\.\./\.\./\.\./index\.md\#https), 509[ldap](\.\./\.\./\.\./\.\./index\.md\#ldap), 510[mailto](\.\./\.\./\.\./\.\./index\.md\#mailto), 511[news](\.\./\.\./\.\./\.\./index\.md\#news), 512[prospero](\.\./\.\./\.\./\.\./index\.md\#prospero), [rfc 5131630](\.\./\.\./\.\./\.\./index\.md\#rfc\_1630), [rfc 5142255](\.\./\.\./\.\./\.\./index\.md\#rfc\_2255), [rfc 5152396](\.\./\.\./\.\./\.\./index\.md\#rfc\_2396), [rfc 5163986](\.\./\.\./\.\./\.\./index\.md\#rfc\_3986), [uri](\.\./\.\./\.\./\.\./index\.md\#uri), 517[url](\.\./\.\./\.\./\.\./index\.md\#url), [wais](\.\./\.\./\.\./\.\./index\.md\#wais), 518[www](\.\./\.\./\.\./\.\./index\.md\#www) 519 520# <a name='category'></a>CATEGORY 521 522Networking 523