1<!-- 2 __ __ _ 3 ___\ \/ /_ __ __ _| |_ 4 / _ \\ /| '_ \ / _` | __| 5 | __// \| |_) | (_| | |_ 6 \___/_/\_\ .__/ \__,_|\__| 7 |_| XML parser 8 9 Copyright (c) 2001 Scott Bronson <bronson@rinspin.com> 10 Copyright (c) 2002-2003 Fred L. Drake, Jr. <fdrake@users.sourceforge.net> 11 Copyright (c) 2009 Karl Waclawek <karl@waclawek.net> 12 Copyright (c) 2016-2024 Sebastian Pipping <sebastian@pipping.org> 13 Copyright (c) 2016 Ardo van Rangelrooij <ardo@debian.org> 14 Copyright (c) 2017 Rhodri James <rhodri@wildebeest.org.uk> 15 Copyright (c) 2020 Joe Orton <jorton@redhat.com> 16 Copyright (c) 2021 Tim Bray <tbray@textuality.com> 17 Unlike most of Expat, 18 this file is copyrighted under the GNU Free Documentation License 1.1. 19--> 20<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" 21 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [ 22 <!ENTITY dhfirstname "<firstname>Scott</firstname>"> 23 <!ENTITY dhsurname "<surname>Bronson</surname>"> 24 <!ENTITY dhdate "<date>November 6, 2024</date>"> 25 <!-- Please adjust this^^ date whenever cutting a new release. --> 26 <!ENTITY dhsection "<manvolnum>1</manvolnum>"> 27 <!ENTITY dhemail "<email>bronson@rinspin.com</email>"> 28 <!ENTITY dhusername "Scott Bronson"> 29 <!ENTITY dhucpackage "<refentrytitle>XMLWF</refentrytitle>"> 30 <!ENTITY dhpackage "xmlwf"> 31 32 <!ENTITY debian "<productname>Debian GNU/Linux</productname>"> 33 <!ENTITY gnu "<acronym>GNU</acronym>"> 34]> 35 36<refentry> 37 <refentryinfo> 38 <address> 39 &dhemail; 40 </address> 41 <author> 42 &dhfirstname; 43 &dhsurname; 44 </author> 45 <copyright> 46 <year>2001</year> 47 <holder>&dhusername;</holder> 48 </copyright> 49 &dhdate; 50 </refentryinfo> 51 <refmeta> 52 &dhucpackage; 53 54 &dhsection; 55 </refmeta> 56 <refnamediv> 57 <refname>&dhpackage;</refname> 58 59 <refpurpose>Determines if an XML document is well-formed</refpurpose> 60 </refnamediv> 61 <refsynopsisdiv> 62 <cmdsynopsis> 63 <command>&dhpackage;</command> 64 <arg><replaceable>OPTIONS</replaceable></arg> 65 <arg><replaceable>FILE</replaceable> ...</arg> 66 </cmdsynopsis> 67 <cmdsynopsis> 68 <command>&dhpackage;</command> 69 <group choice="plain"> 70 <arg><option>-h</option></arg> 71 <arg><option>--help</option></arg> 72 </group> 73 </cmdsynopsis> 74 <cmdsynopsis> 75 <command>&dhpackage;</command> 76 <group choice="plain"> 77 <arg><option>-v</option></arg> 78 <arg><option>--version</option></arg> 79 </group> 80 </cmdsynopsis> 81 </refsynopsisdiv> 82 83 <refsect1> 84 <title>DESCRIPTION</title> 85 86 <para> 87 <command>&dhpackage;</command> uses the Expat library to 88 determine if an XML document is well-formed. It is 89 non-validating. 90 </para> 91 92 <para> 93 If you do not specify any files on the command-line, and you 94 have a recent version of <command>&dhpackage;</command>, the 95 input file will be read from standard input. 96 </para> 97 98 </refsect1> 99 100 <refsect1> 101 <title>WELL-FORMED DOCUMENTS</title> 102 103 <para> 104 A well-formed document must adhere to the 105 following rules: 106 </para> 107 108 <itemizedlist> 109 <listitem><para> 110 The file begins with an XML declaration. For instance, 111 <literal><?xml version="1.0" standalone="yes"?></literal>. 112 <emphasis>NOTE</emphasis>: 113 <command>&dhpackage;</command> does not currently 114 check for a valid XML declaration. 115 </para></listitem> 116 <listitem><para> 117 Every start tag is either empty (<tag/>) 118 or has a corresponding end tag. 119 </para></listitem> 120 <listitem><para> 121 There is exactly one root element. This element must contain 122 all other elements in the document. Only comments, white 123 space, and processing instructions may come after the close 124 of the root element. 125 </para></listitem> 126 <listitem><para> 127 All elements nest properly. 128 </para></listitem> 129 <listitem><para> 130 All attribute values are enclosed in quotes (either single 131 or double). 132 </para></listitem> 133 </itemizedlist> 134 135 <para> 136 If the document has a DTD, and it strictly complies with that 137 DTD, then the document is also considered <emphasis>valid</emphasis>. 138 <command>&dhpackage;</command> is a non-validating parser -- 139 it does not check the DTD. However, it does support 140 external entities (see the <option>-x</option> option). 141 </para> 142 </refsect1> 143 144 <refsect1> 145 <title>OPTIONS</title> 146 147<para> 148When an option includes an argument, you may specify the argument either 149separately ("<option>-d</option> <replaceable>output</replaceable>") or concatenated with the 150option ("<option>-d</option><replaceable>output</replaceable>"). <command>&dhpackage;</command> 151supports both. 152</para> 153 154 <variablelist> 155 156 <varlistentry> 157 <term><option>-a</option> <replaceable>factor</replaceable></term> 158 <listitem> 159 <para> 160 Sets the maximum tolerated amplification factor 161 for protection against billion laughs attacks (default: 100.0). 162 The amplification factor is calculated as .. 163 </para> 164 <literallayout> 165 amplification := (direct + indirect) / direct 166 </literallayout> 167 <para> 168 .. while parsing, whereas 169 <direct> is the number of bytes read 170 from the primary document in parsing and 171 <indirect> is the number of bytes 172 added by expanding entities and reading of external DTD files, 173 combined. 174 </para> 175 <para> 176 <emphasis>NOTE</emphasis>: 177 If you ever need to increase this value for non-attack payload, 178 please file a bug report. 179 </para> 180 </listitem> 181 </varlistentry> 182 183 <varlistentry> 184 <term><option>-b</option> <replaceable>bytes</replaceable></term> 185 <listitem> 186 <para> 187 Sets the number of output bytes (including amplification) 188 needed to activate protection against billion laughs attacks 189 (default: 8 MiB). 190 This can be thought of as an "activation threshold". 191 </para> 192 <para> 193 <emphasis>NOTE</emphasis>: 194 If you ever need to increase this value for non-attack payload, 195 please file a bug report. 196 </para> 197 </listitem> 198 </varlistentry> 199 200 <varlistentry> 201 <term><option>-c</option></term> 202 <listitem> 203 <para> 204 If the input file is well-formed and <command>&dhpackage;</command> 205 doesn't encounter any errors, the input file is simply copied to 206 the output directory unchanged. 207 This implies no namespaces (turns off <option>-n</option>) and 208 requires <option>-d</option> to specify an output directory. 209 </para> 210 </listitem> 211 </varlistentry> 212 213 <varlistentry> 214 <term><option>-d</option> <replaceable>output-dir</replaceable></term> 215 <listitem> 216 <para> 217 Specifies a directory to contain transformed 218 representations of the input files. 219 By default, <option>-d</option> outputs a canonical representation 220 (described below). 221 You can select different output formats using <option>-c</option>, 222 <option>-m</option> and <option>-N</option>. 223 </para> 224 <para> 225 The output filenames will 226 be exactly the same as the input filenames or "STDIN" if the input is 227 coming from standard input. Therefore, you must be careful that the 228 output file does not go into the same directory as the input 229 file. Otherwise, <command>&dhpackage;</command> will delete the 230 input file before it generates the output file (just like running 231 <literal>cat < file > file</literal> in most shells). 232 </para> 233 <para> 234 Two structurally equivalent XML documents have a byte-for-byte 235 identical canonical XML representation. 236 Note that ignorable white space is considered significant and 237 is treated equivalently to data. 238 More on canonical XML can be found at 239 http://www.jclark.com/xml/canonxml.html . 240 </para> 241 </listitem> 242 </varlistentry> 243 244 <varlistentry> 245 <term><option>-e</option> <replaceable>encoding</replaceable></term> 246 <listitem> 247 <para> 248 Specifies the character encoding for the document, overriding 249 any document encoding declaration. <command>&dhpackage;</command> 250 supports four built-in encodings: 251 <literal>US-ASCII</literal>, 252 <literal>UTF-8</literal>, 253 <literal>UTF-16</literal>, and 254 <literal>ISO-8859-1</literal>. 255 Also see the <option>-w</option> option. 256 </para> 257 </listitem> 258 </varlistentry> 259 260 <varlistentry> 261 <term><option>-g</option> <replaceable>bytes</replaceable></term> 262 <listitem> 263 <para> 264 Sets the buffer size to request per call pair to 265 <function>XML_GetBuffer</function> and <function>read</function> 266 (default: 8 KiB). 267 </para> 268 </listitem> 269 </varlistentry> 270 271 <varlistentry> 272 <term><option>-h</option></term> 273 <term><option>--help</option></term> 274 <listitem> 275 <para> 276 Prints short usage information on command <command>&dhpackage;</command>, 277 and then exits. 278 Similar to this man page but more concise. 279 </para> 280 </listitem> 281 </varlistentry> 282 283 <varlistentry> 284 <term><option>-k</option></term> 285 <listitem> 286 <para> 287 When processing multiple files, <command>&dhpackage;</command> 288 by default halts after the the first file with an error. 289 This tells <command>&dhpackage;</command> to report the error 290 but to keep processing. 291 This can be useful, for example, when testing a filter that converts 292 many files to XML and you want to quickly find out which conversions 293 failed. 294 </para> 295 </listitem> 296 </varlistentry> 297 298 <varlistentry> 299 <term><option>-m</option></term> 300 <listitem> 301 <para> 302 Outputs some strange sort of XML file that completely 303 describes the input file, including character positions. 304 Requires <option>-d</option> to specify an output file. 305 </para> 306 </listitem> 307 </varlistentry> 308 309 <varlistentry> 310 <term><option>-n</option></term> 311 <listitem> 312 <para> 313 Turns on namespace processing. (describe namespaces) 314 <option>-c</option> disables namespaces. 315 </para> 316 </listitem> 317 </varlistentry> 318 319 <varlistentry> 320 <term><option>-N</option></term> 321 <listitem> 322 <para> 323 Adds a doctype and notation declarations to canonical XML output. 324 This matches the example output used by the formal XML test cases. 325 Requires <option>-d</option> to specify an output file. 326 </para> 327 </listitem> 328 </varlistentry> 329 330 <varlistentry> 331 <term><option>-p</option></term> 332 <listitem> 333 <para> 334 Tells <command>&dhpackage;</command> to process external DTDs and parameter 335 entities. 336 </para> 337 <para> 338 Normally <command>&dhpackage;</command> never parses parameter 339 entities. <option>-p</option> tells it to always parse them. 340 <option>-p</option> implies <option>-x</option>. 341 </para> 342 </listitem> 343 </varlistentry> 344 345 <varlistentry> 346 <term><option>-q</option></term> 347 <listitem> 348 <para> 349 Disable reparse deferral, and allow quadratic parse runtime 350 on large tokens (default: reparse deferral enabled). 351 </para> 352 </listitem> 353 </varlistentry> 354 355 <varlistentry> 356 <term><option>-r</option></term> 357 <listitem> 358 <para> 359 Normally <command>&dhpackage;</command> memory-maps the XML file 360 before parsing; this can result in faster parsing on many 361 platforms. 362 <option>-r</option> turns off memory-mapping and uses normal file 363 IO calls instead. 364 Of course, memory-mapping is automatically turned off 365 when reading from standard input. 366 </para> 367 <para> 368 Use of memory-mapping can cause some platforms to report 369 substantially higher memory usage for 370 <command>&dhpackage;</command>, but this appears to be a matter of 371 the operating system reporting memory in a strange way; there is 372 not a leak in <command>&dhpackage;</command>. 373 </para> 374 </listitem> 375 </varlistentry> 376 377 <varlistentry> 378 <term><option>-s</option></term> 379 <listitem> 380 <para> 381 Prints an error if the document is not standalone. 382 A document is standalone if it has no external subset and no 383 references to parameter entities. 384 </para> 385 </listitem> 386 </varlistentry> 387 388 <varlistentry> 389 <term><option>-t</option></term> 390 <listitem> 391 <para> 392 Turns on timings. This tells Expat to parse the entire file, 393 but not perform any processing. 394 This gives a fairly accurate idea of the raw speed of Expat itself 395 without client overhead. 396 <option>-t</option> turns off most of the output options 397 (<option>-d</option>, <option>-m</option>, <option>-c</option>, ...). 398 </para> 399 </listitem> 400 </varlistentry> 401 402 <varlistentry> 403 <term><option>-v</option></term> 404 <term><option>--version</option></term> 405 <listitem> 406 <para> 407 Prints the version of the Expat library being used, including some 408 information on the compile-time configuration of the library, and 409 then exits. 410 </para> 411 </listitem> 412 </varlistentry> 413 414 <varlistentry> 415 <term><option>-w</option></term> 416 <listitem> 417 <para> 418 Enables support for Windows code pages. 419 Normally, <command>&dhpackage;</command> will throw an error if it 420 runs across an encoding that it is not equipped to handle itself. With 421 <option>-w</option>, <command>&dhpackage;</command> will try to use a Windows code 422 page. See also <option>-e</option>. 423 </para> 424 </listitem> 425 </varlistentry> 426 427 <varlistentry> 428 <term><option>-x</option></term> 429 <listitem> 430 <para> 431 Turns on parsing external entities. 432 </para> 433<para> 434 Non-validating parsers are not required to resolve external 435 entities, or even expand entities at all. 436 Expat always expands internal entities (?), 437 but external entity parsing must be enabled explicitly. 438 </para> 439 <para> 440 External entities are simply entities that obtain their 441 data from outside the XML file currently being parsed. 442 </para> 443 <para> 444 This is an example of an internal entity: 445<literallayout> 446<!ENTITY vers '1.0.2'> 447</literallayout> 448 </para> 449 <para> 450 And here are some examples of external entities: 451 452<literallayout> 453<!ENTITY header SYSTEM "header-&vers;.xml"> (parsed) 454<!ENTITY logo SYSTEM "logo.png" PNG> (unparsed) 455</literallayout> 456 457 </para> 458 </listitem> 459 </varlistentry> 460 461 <varlistentry> 462 <term><option>--</option></term> 463 <listitem> 464 <para> 465 (Two hyphens.) 466 Terminates the list of options. This is only needed if a filename 467 starts with a hyphen. For example: 468 </para> 469<literallayout> 470&dhpackage; -- -myfile.xml 471</literallayout> 472 <para> 473 will run <command>&dhpackage;</command> on the file 474 <filename>-myfile.xml</filename>. 475 </para> 476 </listitem> 477 </varlistentry> 478 </variablelist> 479 480 <para> 481 Older versions of <command>&dhpackage;</command> do not support 482 reading from standard input. 483 </para> 484 </refsect1> 485 486 <refsect1> 487 <title>OUTPUT</title> 488 <para> 489 <command>&dhpackage;</command> outputs nothing for files which are problem-free. 490 If any input file is not well-formed, or if the output for any 491 input file cannot be opened, <command>&dhpackage;</command> prints a single 492 line describing the problem to standard output. 493 </para> 494 <para> 495 If the <option>-k</option> option is not provided, <command>&dhpackage;</command> 496 halts upon encountering a well-formedness or output-file error. 497 If <option>-k</option> is provided, <command>&dhpackage;</command> continues 498 processing the remaining input files, describing problems found with any of them. 499 </para> 500 </refsect1> 501 502 <refsect1> 503 <title>EXIT STATUS</title> 504 <para>For options <option>-v</option>|<option>--version</option> or <option>-h</option>|<option>--help</option>, <command>&dhpackage;</command> always exits with status code 0. For other cases, the following exit status codes are returned: 505 <variablelist> 506 <varlistentry> 507 <term><option>0</option></term> 508 <listitem><para>The input files are well-formed and the output (if requested) was written successfully.</para> 509 </listitem> 510 </varlistentry> 511 <varlistentry> 512 <term><option>1</option></term> 513 <listitem><para>An internal error occurred.</para> 514 </listitem> 515 </varlistentry> 516 <varlistentry> 517 <term><option>2</option></term> 518 <listitem><para>One or more input files were not well-formed or could not be parsed.</para> 519 </listitem> 520 </varlistentry> 521 <varlistentry> 522 <term><option>3</option></term> 523 <listitem><para>If using the <option>-d</option> option, an error occurred opening an output file.</para> 524 </listitem> 525 </varlistentry> 526 <varlistentry> 527 <term><option>4</option></term> 528 <listitem><para>There was a command-line argument error in how <command>&dhpackage;</command> was invoked.</para> 529 </listitem> 530 </varlistentry> 531 </variablelist> 532 </para> 533 </refsect1> 534 535 536 <refsect1> 537 <title>BUGS</title> 538 <para> 539 The errors should go to standard error, not standard output. 540 </para> 541 <para> 542 There should be a way to get <option>-d</option> to send its 543 output to standard output rather than forcing the user to send 544 it to a file. 545 </para> 546 <para> 547 I have no idea why anyone would want to use the 548 <option>-d</option>, <option>-c</option>, and 549 <option>-m</option> options. If someone could explain it to 550 me, I'd like to add this information to this manpage. 551 </para> 552 </refsect1> 553 554 <refsect1> 555 <title>SEE ALSO</title> 556 <para> 557 558<literallayout> 559The Expat home page: https://libexpat.github.io/ 560The W3 XML 1.0 specification (fourth edition): https://www.w3.org/TR/2006/REC-xml-20060816/ 561Billion laughs attack: https://en.wikipedia.org/wiki/Billion_laughs_attack 562</literallayout> 563 564 </para> 565 </refsect1> 566 567 <refsect1> 568 <title>AUTHOR</title> 569 <para> 570 This manual page was originally written by &dhusername; &dhemail; 571 in December 2001 for 572 the &debian; system (but may be used by others). Permission is 573 granted to copy, distribute and/or modify this document under 574 the terms of the <acronym>GNU</acronym> Free Documentation 575 License, Version 1.1. 576 </para> 577 </refsect1> 578</refentry> 579
