1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>POSIX Basic Regular Expression Syntax</title> 5<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Boost.Regex 5.1.4"> 8<link rel="up" href="../syntax.html" title="Regular Expression Syntax"> 9<link rel="prev" href="basic_extended.html" title="POSIX Extended Regular Expression Syntax"> 10<link rel="next" href="character_classes.html" title="Character Class Names"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../index.html">Home</a></td> 16<td align="center"><a 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Regular Expression Syntax">POSIX Basic Regular 28 Expression Syntax</a> 29</h3></div></div></div> 30<h4> 31<a name="boost_regex.syntax.basic_syntax.h0"></a> 32 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.synopsis"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.synopsis">Synopsis</a> 33 </h4> 34<p> 35 The POSIX-Basic regular expression syntax is used by the Unix utility <code class="computeroutput"><span class="identifier">sed</span></code>, and variations are used by <code class="computeroutput"><span class="identifier">grep</span></code> and <code class="computeroutput"><span class="identifier">emacs</span></code>. 36 You can construct POSIX basic regular expressions in Boost.Regex by passing 37 the flag <code class="computeroutput"><span class="identifier">basic</span></code> to the regex 38 constructor (see <a class="link" href="../ref/syntax_option_type.html" title="syntax_option_type"><code class="computeroutput"><span class="identifier">syntax_option_type</span></code></a>), for example: 39 </p> 40<pre class="programlisting"><span class="comment">// e1 is a case sensitive POSIX-Basic expression:</span> 41<span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="identifier">e1</span><span class="special">(</span><span class="identifier">my_expression</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">basic</span><span class="special">);</span> 42<span class="comment">// e2 a case insensitive POSIX-Basic expression:</span> 43<span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="identifier">e2</span><span class="special">(</span><span class="identifier">my_expression</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">basic</span><span class="special">|</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">icase</span><span class="special">);</span> 44</pre> 45<a name="boost_regex.posix_basic"></a><h4> 46<a name="boost_regex.syntax.basic_syntax.h1"></a> 47 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.posix_basic_syntax"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.posix_basic_syntax">POSIX 48 Basic Syntax</a> 49 </h4> 50<p> 51 In POSIX-Basic regular expressions, all characters are match themselves except 52 for the following special characters: 53 </p> 54<pre class="programlisting">.[\*^$</pre> 55<h5> 56<a name="boost_regex.syntax.basic_syntax.h2"></a> 57 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.wildcard"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.wildcard">Wildcard:</a> 58 </h5> 59<p> 60 The single character '.' when used outside of a character set will match 61 any single character except: 62 </p> 63<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 64<li class="listitem"> 65 The NULL character when the flag <code class="computeroutput"><span class="identifier">match_no_dot_null</span></code> 66 is passed to the matching algorithms. 67 </li> 68<li class="listitem"> 69 The newline character when the flag <code class="computeroutput"><span class="identifier">match_not_dot_newline</span></code> 70 is passed to the matching algorithms. 71 </li> 72</ul></div> 73<h5> 74<a name="boost_regex.syntax.basic_syntax.h3"></a> 75 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.anchors"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.anchors">Anchors:</a> 76 </h5> 77<p> 78 A '^' character shall match the start of a line when used as the first character 79 of an expression, or the first character of a sub-expression. 80 </p> 81<p> 82 A '$' character shall match the end of a line when used as the last character 83 of an expression, or the last character of a sub-expression. 84 </p> 85<h5> 86<a name="boost_regex.syntax.basic_syntax.h4"></a> 87 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.marked_sub_expressions"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.marked_sub_expressions">Marked sub-expressions:</a> 88 </h5> 89<p> 90 A section beginning <code class="computeroutput"><span class="special">\(</span></code> and ending 91 <code class="computeroutput"><span class="special">\)</span></code> acts as a marked sub-expression. 92 Whatever matched the sub-expression is split out in a separate field by the 93 matching algorithms. Marked sub-expressions can also repeated, or referred-to 94 by a back-reference. 95 </p> 96<h5> 97<a name="boost_regex.syntax.basic_syntax.h5"></a> 98 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.repeats"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.repeats">Repeats:</a> 99 </h5> 100<p> 101 Any atom (a single character, a marked sub-expression, or a character class) 102 can be repeated with the * operator. 103 </p> 104<p> 105 For example <code class="computeroutput"><span class="identifier">a</span><span class="special">*</span></code> 106 will match any number of letter a's repeated zero or more times (an atom 107 repeated zero times matches an empty string), so the expression <code class="computeroutput"><span class="identifier">a</span><span class="special">*</span><span class="identifier">b</span></code> 108 will match any of the following: 109 </p> 110<pre class="programlisting">b 111ab 112aaaaaaaab 113</pre> 114<p> 115 An atom can also be repeated with a bounded repeat: 116 </p> 117<p> 118 <code class="computeroutput"><span class="identifier">a</span><span class="special">\{</span><span class="identifier">n</span><span class="special">\}</span></code> Matches 119 'a' repeated exactly n times. 120 </p> 121<p> 122 <code class="computeroutput"><span class="identifier">a</span><span class="special">\{</span><span class="identifier">n</span><span class="special">,\}</span></code> Matches 123 'a' repeated n or more times. 124 </p> 125<p> 126 <code class="computeroutput"><span class="identifier">a</span><span class="special">\{</span><span class="identifier">n</span><span class="special">,</span> <span class="identifier">m</span><span class="special">\}</span></code> Matches 'a' repeated between n and m times 127 inclusive. 128 </p> 129<p> 130 For example: 131 </p> 132<pre class="programlisting">^a{2,3}$</pre> 133<p> 134 Will match either of: 135 </p> 136<pre class="programlisting">aa 137aaa 138</pre> 139<p> 140 But neither of: 141 </p> 142<pre class="programlisting">a 143aaaa 144</pre> 145<p> 146 It is an error to use a repeat operator, if the preceding construct can not 147 be repeated, for example: 148 </p> 149<pre class="programlisting">a(*)</pre> 150<p> 151 Will raise an error, as there is nothing for the * operator to be applied 152 to. 153 </p> 154<h5> 155<a name="boost_regex.syntax.basic_syntax.h6"></a> 156 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.back_references"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.back_references">Back 157 references:</a> 158 </h5> 159<p> 160 An escape character followed by a digit <span class="emphasis"><em>n</em></span>, where <span class="emphasis"><em>n</em></span> 161 is in the range 1-9, matches the same string that was matched by sub-expression 162 <span class="emphasis"><em>n</em></span>. For example the expression: 163 </p> 164<pre class="programlisting">^\(a*\)[^a]*\1$</pre> 165<p> 166 Will match the string: 167 </p> 168<pre class="programlisting">aaabbaaa</pre> 169<p> 170 But not the string: 171 </p> 172<pre class="programlisting">aaabba</pre> 173<h5> 174<a name="boost_regex.syntax.basic_syntax.h7"></a> 175 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.character_sets"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.character_sets">Character 176 sets:</a> 177 </h5> 178<p> 179 A character set is a bracket-expression starting with [ and ending with ], 180 it defines a set of characters, and matches any single character that is 181 a member of that set. 182 </p> 183<p> 184 A bracket expression may contain any combination of the following: 185 </p> 186<h6> 187<a name="boost_regex.syntax.basic_syntax.h8"></a> 188 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.single_characters"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.single_characters">Single 189 characters:</a> 190 </h6> 191<p> 192 For example <code class="computeroutput"><span class="special">[</span><span class="identifier">abc</span><span class="special">]</span></code>, will match any of the characters 'a', 'b', 193 or 'c'. 194 </p> 195<h6> 196<a name="boost_regex.syntax.basic_syntax.h9"></a> 197 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.character_ranges"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.character_ranges">Character 198 ranges:</a> 199 </h6> 200<p> 201 For example <code class="computeroutput"><span class="special">[</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span><span class="special">]</span></code> 202 will match any single character in the range 'a' to 'c'. By default, for 203 POSIX-Basic regular expressions, a character <span class="emphasis"><em>x</em></span> is within 204 the range <span class="emphasis"><em>y</em></span> to <span class="emphasis"><em>z</em></span>, if it collates 205 within that range; this results in locale specific behavior. This behavior 206 can be turned off by unsetting the <code class="computeroutput"><span class="identifier">collate</span></code> 207 option flag when constructing the regular expression - in which case whether 208 a character appears within a range is determined by comparing the code points 209 of the characters only. 210 </p> 211<h6> 212<a name="boost_regex.syntax.basic_syntax.h10"></a> 213 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.negation"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.negation">Negation:</a> 214 </h6> 215<p> 216 If the bracket-expression begins with the ^ character, then it matches the 217 complement of the characters it contains, for example <code class="computeroutput"><span class="special">[^</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span><span class="special">]</span></code> matches any character that is not in the 218 range a-c. 219 </p> 220<h6> 221<a name="boost_regex.syntax.basic_syntax.h11"></a> 222 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.character_classes"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.character_classes">Character 223 classes:</a> 224 </h6> 225<p> 226 An expression of the form <code class="computeroutput"><span class="special">[[:</span><span class="identifier">name</span><span class="special">:]]</span></code> 227 matches the named character class "name", for example <code class="computeroutput"><span class="special">[[:</span><span class="identifier">lower</span><span class="special">:]]</span></code> matches any lower case character. See 228 <a class="link" href="character_classes.html" title="Character Class Names">character class names</a>. 229 </p> 230<h6> 231<a name="boost_regex.syntax.basic_syntax.h12"></a> 232 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.collating_elements"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.collating_elements">Collating 233 Elements:</a> 234 </h6> 235<p> 236 An expression of the form <code class="computeroutput"><span class="special">[[.</span><span class="identifier">col</span><span class="special">.]</span></code> matches 237 the collating element <span class="emphasis"><em>col</em></span>. A collating element is any 238 single character, or any sequence of characters that collates as a single 239 unit. Collating elements may also be used as the end point of a range, for 240 example: <code class="computeroutput"><span class="special">[[.</span><span class="identifier">ae</span><span class="special">.]-</span><span class="identifier">c</span><span class="special">]</span></code> 241 matches the character sequence "ae", plus any single character 242 in the range "ae"-c, assuming that "ae" is treated as 243 a single collating element in the current locale. 244 </p> 245<p> 246 Collating elements may be used in place of escapes (which are not normally 247 allowed inside character sets), for example <code class="computeroutput"><span class="special">[[.^.]</span><span class="identifier">abc</span><span class="special">]</span></code> would 248 match either one of the characters 'abc^'. 249 </p> 250<p> 251 As an extension, a collating element may also be specified via its symbolic 252 name, for example: 253 </p> 254<pre class="programlisting">[[.NUL.]]</pre> 255<p> 256 matches a 'NUL' character. See <a class="link" href="collating_names.html" title="Collating Names">collating 257 element names</a>. 258 </p> 259<h6> 260<a name="boost_regex.syntax.basic_syntax.h13"></a> 261 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.equivalence_classes"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.equivalence_classes">Equivalence 262 classes:</a> 263 </h6> 264<p> 265 An expression of the form <code class="computeroutput"><span class="special">[[=</span><span class="identifier">col</span><span class="special">=]]</span></code>, 266 matches any character or collating element whose primary sort key is the 267 same as that for collating element <span class="emphasis"><em>col</em></span>, as with collating 268 elements the name <span class="emphasis"><em>col</em></span> may be a <a class="link" href="collating_names.html" title="Collating Names">collating 269 symbolic name</a>. A primary sort key is one that ignores case, accentation, 270 or locale-specific tailorings; so for example <code class="computeroutput"><span class="special">[[=</span><span class="identifier">a</span><span class="special">=]]</span></code> matches 271 any of the characters: a, À, Á, Â, Ã, Ä, Å, A, à, á, â, ã, ä and å. Unfortunately implementation 272 of this is reliant on the platform's collation and localisation support; 273 this feature can not be relied upon to work portably across all platforms, 274 or even all locales on one platform. 275 </p> 276<h6> 277<a name="boost_regex.syntax.basic_syntax.h14"></a> 278 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.combinations"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.combinations">Combinations:</a> 279 </h6> 280<p> 281 All of the above can be combined in one character set declaration, for example: 282 <code class="computeroutput"><span class="special">[[:</span><span class="identifier">digit</span><span class="special">:]</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span><span class="special">[.</span><span class="identifier">NUL</span><span class="special">.]].</span></code> 283 </p> 284<h5> 285<a name="boost_regex.syntax.basic_syntax.h15"></a> 286 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.escapes"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.escapes">Escapes</a> 287 </h5> 288<p> 289 With the exception of the escape sequences \{, \}, \(, and \), which are 290 documented above, an escape followed by any character matches that character. 291 This can be used to make the special characters 292 </p> 293<pre class="programlisting">.[\*^$</pre> 294<p> 295 "ordinary". Note that the escape character loses its special meaning 296 inside a character set, so <code class="computeroutput"><span class="special">[\^]</span></code> 297 will match either a literal '\' or a '^'. 298 </p> 299<h4> 300<a name="boost_regex.syntax.basic_syntax.h16"></a> 301 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.what_gets_matched"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.what_gets_matched">What 302 Gets Matched</a> 303 </h4> 304<p> 305 When there is more that one way to match a regular expression, the "best" 306 possible match is obtained using the <a class="link" href="leftmost_longest_rule.html" title="The Leftmost Longest Rule">leftmost-longest 307 rule</a>. 308 </p> 309<h4> 310<a name="boost_regex.syntax.basic_syntax.h17"></a> 311 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.variations"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.variations">Variations</a> 312 </h4> 313<a name="boost_regex.grep_syntax"></a><h5> 314<a name="boost_regex.syntax.basic_syntax.h18"></a> 315 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.grep"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.grep">Grep</a> 316 </h5> 317<p> 318 When an expression is compiled with the flag <code class="computeroutput"><span class="identifier">grep</span></code> 319 set, then the expression is treated as a newline separated list of <a class="link" href="basic_syntax.html#boost_regex.posix_basic">POSIX-Basic expressions</a>, a match 320 is found if any of the expressions in the list match, for example: 321 </p> 322<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="identifier">e</span><span class="special">(</span><span class="string">"abc\ndef"</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">grep</span><span class="special">);</span> 323</pre> 324<p> 325 will match either of the <a class="link" href="basic_syntax.html#boost_regex.posix_basic">POSIX-Basic 326 expressions</a> "abc" or "def". 327 </p> 328<p> 329 As its name suggests, this behavior is consistent with the Unix utility grep. 330 </p> 331<h5> 332<a name="boost_regex.syntax.basic_syntax.h19"></a> 333 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.emacs"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.emacs">emacs</a> 334 </h5> 335<p> 336 In addition to the <a class="link" href="basic_syntax.html#boost_regex.posix_basic">POSIX-Basic features</a> 337 the following characters are also special: 338 </p> 339<div class="informaltable"><table class="table"> 340<colgroup> 341<col> 342<col> 343</colgroup> 344<thead><tr> 345<th> 346 <p> 347 Character 348 </p> 349 </th> 350<th> 351 <p> 352 Description 353 </p> 354 </th> 355</tr></thead> 356<tbody> 357<tr> 358<td> 359 <p> 360 + 361 </p> 362 </td> 363<td> 364 <p> 365 repeats the preceding atom one or more times. 366 </p> 367 </td> 368</tr> 369<tr> 370<td> 371 <p> 372 ? 373 </p> 374 </td> 375<td> 376 <p> 377 repeats the preceding atom zero or one times. 378 </p> 379 </td> 380</tr> 381<tr> 382<td> 383 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> 384 ? 385 </li></ul></div> 386 </td> 387<td> 388 <p> 389 A non-greedy version of *. 390 </p> 391 </td> 392</tr> 393<tr> 394<td> 395 <p> 396 +? 397 </p> 398 </td> 399<td> 400 <p> 401 A non-greedy version of +. 402 </p> 403 </td> 404</tr> 405<tr> 406<td> 407 <p> 408 ?? 409 </p> 410 </td> 411<td> 412 <p> 413 A non-greedy version of ?. 414 </p> 415 </td> 416</tr> 417</tbody> 418</table></div> 419<p> 420 And the following escape sequences are also recognised: 421 </p> 422<div class="informaltable"><table class="table"> 423<colgroup> 424<col> 425<col> 426</colgroup> 427<thead><tr> 428<th> 429 <p> 430 Escape 431 </p> 432 </th> 433<th> 434 <p> 435 Description 436 </p> 437 </th> 438</tr></thead> 439<tbody> 440<tr> 441<td> 442 <p> 443 \| 444 </p> 445 </td> 446<td> 447 <p> 448 specifies an alternative. 449 </p> 450 </td> 451</tr> 452<tr> 453<td> 454 <p> 455 \(?: ... ) 456 </p> 457 </td> 458<td> 459 <p> 460 is a non-marking grouping construct - allows you to lexically group 461 something without spitting out an extra sub-expression. 462 </p> 463 </td> 464</tr> 465<tr> 466<td> 467 <p> 468 \w 469 </p> 470 </td> 471<td> 472 <p> 473 matches any word character. 474 </p> 475 </td> 476</tr> 477<tr> 478<td> 479 <p> 480 \W 481 </p> 482 </td> 483<td> 484 <p> 485 matches any non-word character. 486 </p> 487 </td> 488</tr> 489<tr> 490<td> 491 <p> 492 \sx 493 </p> 494 </td> 495<td> 496 <p> 497 matches any character in the syntax group x, the following emacs 498 groupings are supported: 's', ' ', '_', 'w', '.', ')', '(', '"', 499 '\'', '>' and '<'. Refer to the emacs docs for details. 500 </p> 501 </td> 502</tr> 503<tr> 504<td> 505 <p> 506 \Sx 507 </p> 508 </td> 509<td> 510 <p> 511 matches any character not in the syntax grouping x. 512 </p> 513 </td> 514</tr> 515<tr> 516<td> 517 <p> 518 \c and \C 519 </p> 520 </td> 521<td> 522 <p> 523 These are not supported. 524 </p> 525 </td> 526</tr> 527<tr> 528<td> 529 <p> 530 \` 531 </p> 532 </td> 533<td> 534 <p> 535 matches zero characters only at the start of a buffer (or string 536 being matched). 537 </p> 538 </td> 539</tr> 540<tr> 541<td> 542 <p> 543 \' 544 </p> 545 </td> 546<td> 547 <p> 548 matches zero characters only at the end of a buffer (or string 549 being matched). 550 </p> 551 </td> 552</tr> 553<tr> 554<td> 555 <p> 556 \b 557 </p> 558 </td> 559<td> 560 <p> 561 matches zero characters at a word boundary. 562 </p> 563 </td> 564</tr> 565<tr> 566<td> 567 <p> 568 \B 569 </p> 570 </td> 571<td> 572 <p> 573 matches zero characters, not at a word boundary. 574 </p> 575 </td> 576</tr> 577<tr> 578<td> 579 <p> 580 \< 581 </p> 582 </td> 583<td> 584 <p> 585 matches zero characters only at the start of a word. 586 </p> 587 </td> 588</tr> 589<tr> 590<td> 591 <p> 592 \> 593 </p> 594 </td> 595<td> 596 <p> 597 matches zero characters only at the end of a word. 598 </p> 599 </td> 600</tr> 601</tbody> 602</table></div> 603<p> 604 Finally, you should note that emacs style regular expressions are matched 605 according to the <a class="link" href="perl_syntax.html#boost_regex.syntax.perl_syntax.what_gets_matched">Perl 606 "depth first search" rules</a>. Emacs expressions are matched 607 this way because they contain Perl-like extensions, that do not interact 608 well with the <a class="link" href="leftmost_longest_rule.html" title="The Leftmost Longest Rule">POSIX-style 609 leftmost-longest rule</a>. 610 </p> 611<h4> 612<a name="boost_regex.syntax.basic_syntax.h20"></a> 613 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.options"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.options">Options</a> 614 </h4> 615<p> 616 There are a <a class="link" href="../ref/syntax_option_type/syntax_option_type_basic.html" title="Options for POSIX Basic Regular Expressions">variety 617 of flags</a> that may be combined with the <code class="computeroutput"><span class="identifier">basic</span></code> 618 and <code class="computeroutput"><span class="identifier">grep</span></code> options when constructing 619 the regular expression, in particular note that the <a class="link" href="../ref/syntax_option_type/syntax_option_type_basic.html" title="Options for POSIX Basic Regular Expressions"><code class="computeroutput"><span class="identifier">newline_alt</span></code>, <code class="computeroutput"><span class="identifier">no_char_classes</span></code>, 620 <code class="computeroutput"><span class="identifier">no</span><span class="special">-</span><span class="identifier">intervals</span></code>, <code class="computeroutput"><span class="identifier">bk_plus_qm</span></code> 621 and <code class="computeroutput"><span class="identifier">bk_plus_vbar</span></code></a> options 622 all alter the syntax, while the <a class="link" href="../ref/syntax_option_type/syntax_option_type_basic.html" title="Options for POSIX Basic Regular Expressions"><code class="computeroutput"><span class="identifier">collate</span></code> and <code class="computeroutput"><span class="identifier">icase</span></code> 623 options</a> modify how the case and locale sensitivity are to be applied. 624 </p> 625<h4> 626<a name="boost_regex.syntax.basic_syntax.h21"></a> 627 <span class="phrase"><a name="boost_regex.syntax.basic_syntax.references"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.references">References</a> 628 </h4> 629<p> 630 <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap09.html" target="_top">IEEE 631 Std 1003.1-2001, Portable Operating System Interface (POSIX ), Base Definitions 632 and Headers, Section 9, Regular Expressions (FWD.1).</a> 633 </p> 634<p> 635 <a href="http://www.opengroup.org/onlinepubs/000095399/utilities/grep.html" target="_top">IEEE 636 Std 1003.1-2001, Portable Operating System Interface (POSIX ), Shells and 637 Utilities, Section 4, Utilities, grep (FWD.1).</a> 638 </p> 639<p> 640 <a href="http://www.gnu.org/software/emacs/" target="_top">Emacs Version 21.3.</a> 641 </p> 642</div> 643<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 644<td align="left"></td> 645<td align="right"><div class="copyright-footer">Copyright © 1998-2013 John Maddock<p> 646 Distributed under the Boost Software License, Version 1.0. (See accompanying 647 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 648 </p> 649</div></td> 650</tr></table> 651<hr> 652<div class="spirit-nav"> 653<a accesskey="p" href="basic_extended.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../syntax.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="character_classes.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 654</div> 655</body> 656</html> 657
