/[pcre]/code/trunk/doc/pcrepattern.3

Diff of /code/trunk/doc/pcrepattern.3

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-revision 572 by ph10,
Wed Nov 17 17:55:57 2010 UTC
+revision 575 by ph10,
Sun Nov 21 12:55:42 2010 UTC
 Line 182 
 The following sections describe the use
  .rs
  .sp
  The backslash character has several uses. Firstly, if it is followed by a
- non-alphanumeric character, it takes away any special meaning that character
+ character that is not a number or a letter, it takes away any special meaning
- may have. This use of backslash as an escape character applies both inside and
+ that character may have. This use of backslash as an escape character applies
- outside character classes.
+ both inside and outside character classes.
  .P
  For example, if you want to match a * character, you write \e* in the pattern.
  This escaping action applies whether or not the following character would
 Line 192 
 otherwise be interpreted as a metacharac
  non-alphanumeric with backslash to specify that it stands for itself. In
  particular, if you want to match a backslash, you write \e\e.
  .P
+ In UTF-8 mode, only ASCII numbers and letters have any special meaning after a
+ backslash. All other characters (in particular, those whose codepoints are
+ greater than 127) are treated as literals.
+ .P
  If a pattern is compiled with the PCRE_EXTENDED option, whitespace in the
  pattern (other than in a character class) and characters between a # outside
  a character class and the next newline are ignored. An escaping backslash can
-Line 225 
 but when a pattern is being prepared by
+Line 229 
 but when a pattern is being prepared by
  one of the following escape sequences than the binary character it represents:
  .sp
    \ea        alarm, that is, the BEL character (hex 07)
-   \ecx       "control-x", where x is any character
+   \ecx       "control-x", where x is any ASCII character
    \ee        escape (hex 1B)
    \ef        formfeed (hex 0C)
    \en        linefeed (hex 0A)
-Line 237 
 one of the following escape sequences th
+Line 241 
 one of the following escape sequences th
  .sp
  The precise effect of \ecx is as follows: if x is a lower case letter, it
  is converted to upper case. Then bit 6 of the character (hex 40) is inverted.
- Thus \ecz becomes hex 1A, but \ec{ becomes hex 3B, while \ec; becomes hex
+ Thus \ecz becomes hex 1A (z is 7A), but \ec{ becomes hex 3B ({ is 7B), while
-B.
+ \ec; becomes hex 7B (; is 3B). If the byte following \ec has a value greater
+ than 127, a compile-time error occurs. This locks out non-ASCII characters in
+ both byte mode and UTF-8 mode. (When PCRE is compiled in EBCDIC mode, all byte
+ values are valid. A lower case letter is converted to upper case, and then the
+xc0 bits are flipped.)
  .P
  After \ex, from zero to two hexadecimal digits are read (letters can be in
  upper or lower case). Any number of hexadecimal digits may appear between \ex{
-Line 1044 
 characters in both cases. In UTF-8 mode,
+Line 1052 
 characters in both cases. In UTF-8 mode,
  characters with values greater than 128 only when it is compiled with Unicode
  property support.
  .P
- The character types \ed, \eD, \eh, \eH, \ep, \eP, \es, \eS, \ev, \eV, \ew, and
+ The character escape sequences \ed, \eD, \eh, \eH, \ep, \eP, \es, \eS, \ev,
- \eW may also appear in a character class, and add the characters that they
+ \eV, \ew, and \eW may appear in a character class, and add the characters that
- match to the class. For example, [\edABCDEF] matches any hexadecimal digit. A
+ they match to the class. For example, [\edABCDEF] matches any hexadecimal
- circumflex can conveniently be used with the upper case character types to
+ digit. In UTF-8 mode, the PCRE_UCP option affects the meanings of \ed, \es, \ew
+ and their upper case partners, just as it does when they appear outside a
+ character class, as described in the section entitled
+ .\" HTML <a href="#genericchartypes">
+ .\" </a>
+ "Generic character types"
+ .\"
+ above. The escape sequence \eb has a different meaning inside a character
+ class; it matches the backspace character. The sequences \eB, \eN, \eR, and \eX
+ are not special inside a character class. Like any other unrecognized escape
+ sequences, they are treated as the literal characters "B", "N", "R", and "X" by
+ default, but cause an error if the PCRE_EXTRA option is set.
+ .P
+ A circumflex can conveniently be used with the upper case character types to
  specify a more restricted set of characters than the matching lower case type.
- For example, the class [^\eW_] matches any letter or digit, but not underscore.
+ For example, the class [^\eW_] matches any letter or digit, but not underscore,
+ whereas [\ew] includes underscore. A positive character class should be read as
+ "something OR something OR ..." and a negative class as "NOT something AND NOT
+ something AND NOT ...".
  .P
  The only metacharacters that are recognized in character classes are backslash,
  hyphen (only where it can be interpreted as specifying a range), circumflex
-Line 2718 
 Cambridge CB2 3QH, England.
+Line 2742 
 Cambridge CB2 3QH, England.
  .rs
  .sp
  .nf
- Last updated: 17 November 2010
+ Last updated: 21 November 2010
  Copyright (c) 1997-2010 University of Cambridge.
  .fi

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