/[pcre]/code/trunk/doc/pcre.html

Diff of /code/trunk/doc/pcre.html

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-revision 46 by nigel,
Sat Feb 24 21:39:21 2007 UTC
+revision 47 by nigel,
Sat Feb 24 21:39:29 2007 UTC
 Line 430 
 no back references.
  <P>
  Return information about the first character of any matched string, for a
  non-anchored pattern. If there is a fixed first character, e.g. from a pattern
- such as (cat|cow|coyote), then it is returned in the integer pointed to by
+ such as (cat|cow|coyote), it is returned in the integer pointed to by
  <I>where</I>. Otherwise, if either
  </P>
  <P>
 Line 442 
 starts with "^", or
  (if it were set, the pattern would be anchored),
  </P>
  <P>
- then -1 is returned, indicating that the pattern matches only at the
+ -1 is returned, indicating that the pattern matches only at the start of a
- start of a subject string or after any "\n" within the string. Otherwise -2 is
+ subject string or after any "\n" within the string. Otherwise -2 is returned.
- returned. For anchored patterns, -2 is returned.
+ For anchored patterns, -2 is returned.
  </P>
  <P>
  <PRE>
 Line 734 
 is a pointer to the vector of integer of
  were captured by the match, including the substring that matched the entire
  regular expression. This is the value returned by <B>pcre_exec</B> if it
  is greater than zero. If <B>pcre_exec()</B> returned zero, indicating that it
- ran out of space in <I>ovector</I>, then the value passed as
+ ran out of space in <I>ovector</I>, the value passed as <I>stringcount</I> should
- <I>stringcount</I> should be the size of the vector divided by three.
+ be the size of the vector divided by three.
  </P>
  <P>
  The functions <B>pcre_copy_substring()</B> and <B>pcre_get_substring()</B>
 Line 857 
 patterns using the non-Perl item (?R).
  with the settings of captured strings when part of a pattern is repeated. For
  example, matching "aba" against the pattern /^(a(b)?)+$/ sets $2 to the value
  "b", but matching "aabbaa" against /^(aa(bb)?)+$/ leaves $2 unset. However, if
- the pattern is changed to /^(aa(b(b))?)+$/ then $2 (and $3) get set.
+ the pattern is changed to /^(aa(b(b))?)+$/ then $2 (and $3) are set.
  </P>
  <P>
  In Perl 5.004 $2 is set in both cases, and that is also true of PCRE. If in the
 Line 1186 
 end of the subject in both modes, and if
  <P>
  Outside a character class, a dot in the pattern matches any one character in
  the subject, including a non-printing character, but not (by default) newline.
- If the PCRE_DOTALL option is set, then dots match newlines as well. The
+ If the PCRE_DOTALL option is set, dots match newlines as well. The handling of
- handling of dot is entirely independent of the handling of circumflex and
+ dot is entirely independent of the handling of circumflex and dollar, the only
- dollar, the only relationship being that they both involve newline characters.
+ relationship being that they both involve newline characters. Dot has no
- Dot has no special meaning in a character class.
+ special meaning in a character class.
  </P>
  <LI><A NAME="SEC17" HREF="#TOC1">SQUARE BRACKETS</A>
  <P>
 Line 1580 
 fails, because it matches the entire str
  item.
  </P>
  <P>
- However, if a quantifier is followed by a question mark, then it ceases to be
+ However, if a quantifier is followed by a question mark, it ceases to be
  greedy, and instead matches the minimum number of times possible, so the
  pattern
  </P>
 Line 1605 
 which matches one digit by preference, b
  way the rest of the pattern matches.
  </P>
  <P>
- If the PCRE_UNGREEDY option is set (an option which is not available in Perl)
+ If the PCRE_UNGREEDY option is set (an option which is not available in Perl),
- then the quantifiers are not greedy by default, but individual ones can be made
+ the quantifiers are not greedy by default, but individual ones can be made
  greedy by following them with a question mark. In other words, it inverts the
  default behaviour.
  </P>
 Line 1617 
 compiled pattern, in proportion to the s
  </P>
  <P>
  If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equivalent
- to Perl's /s) is set, thus allowing the . to match newlines, then the pattern
+ to Perl's /s) is set, thus allowing the . to match newlines, the pattern is
- is implicitly anchored, because whatever follows will be tried against every
+ implicitly anchored, because whatever follows will be tried against every
  character position in the subject string, so there is no point in retrying the
  overall match at any position after the first. PCRE treats such a pattern as
  though it were preceded by \A. In cases where it is known that the subject
 Line 1677 
 itself. So the pattern
  <P>
  matches "sense and sensibility" and "response and responsibility", but not
  "sense and responsibility". If caseful matching is in force at the time of the
- back reference, then the case of letters is relevant. For example,
+ back reference, the case of letters is relevant. For example,
  </P>
  <P>
  <PRE>
 Line 1690 
 capturing subpattern is matched caseless
  </P>
  <P>
  There may be more than one back reference to the same subpattern. If a
- subpattern has not actually been used in a particular match, then any back
+ subpattern has not actually been used in a particular match, any back
  references to it always fail. For example, the pattern
  </P>
  <P>
 Line 1702 
 references to it always fail. For exampl
  always fails if it starts to match "a" rather than "bc". Because there may be
  up to 99 back references, all digits following the backslash are taken
  as part of a potential back reference number. If the pattern continues with a
- digit character, then some delimiter must be used to terminate the back
+ digit character, some delimiter must be used to terminate the back reference.
- reference. If the PCRE_EXTENDED option is set, this can be whitespace.
+ If the PCRE_EXTENDED option is set, this can be whitespace. Otherwise an empty
- Otherwise an empty comment can be used.
+ comment can be used.
  </P>
  <P>
  A back reference that occurs inside the parentheses to which it refers fails
 Line 1836 
 Several assertions (of any sort) may occ
  matches "foo" preceded by three digits that are not "999". Notice that each of
  the assertions is applied independently at the same point in the subject
  string. First there is a check that the previous three characters are all
- digits, then there is a check that the same three characters are not "999".
+ digits, and then there is a check that the same three characters are not "999".
  This pattern does <I>not</I> match "foo" preceded by six characters, the first
  of which are digits and the last three of which are not "999". For example, it
  doesn't match "123abcfoo". A pattern to do that is
 Line 1957 
 what follows matches the rest of the pat
  </PRE>
  </P>
  <P>
- then the initial .* matches the entire string at first, but when this fails
+ the initial .* matches the entire string at first, but when this fails (because
- (because there is no following "a"), it backtracks to match all but the last
+ there is no following "a"), it backtracks to match all but the last character,
- character, then all but the last two characters, and so on. Once again the
+ then all but the last two characters, and so on. Once again the search for "a"
- search for "a" covers the entire string, from right to left, so we are no
+ covers the entire string, from right to left, so we are no better off. However,
- better off. However, if the pattern is written as
+ if the pattern is written as
  </P>
  <P>
  <PRE>
 Line 1969 
 better off. However, if the pattern is w
  </PRE>
  </P>
  <P>
- then there can be no backtracking for the .* item; it can match only the entire
+ there can be no backtracking for the .* item; it can match only the entire
  string. The subsequent lookbehind assertion does a single test on the last four
  characters. If it fails, the match fails immediately. For long strings, this
  approach makes a significant difference to the processing time.
 Line 2032 
 subpattern, a compile-time error occurs.
  </P>
  <P>
  There are two kinds of condition. If the text between the parentheses consists
- of a sequence of digits, then the condition is satisfied if the capturing
+ of a sequence of digits, the condition is satisfied if the capturing subpattern
- subpattern of that number has previously matched. Consider the following
+ of that number has previously matched. Consider the following pattern, which
- pattern, which contains non-significant white space to make it more readable
+ contains non-significant white space to make it more readable (assume the
- (assume the PCRE_EXTENDED option) and to divide it into three parts for ease
+ PCRE_EXTENDED option) and to divide it into three parts for ease of discussion:
- of discussion:
  </P>
  <P>
  <PRE>
-Line 2157 
 on at the top level. If additional paren
+Line 2156 
 on at the top level. If additional paren
       ^                        ^
       ^                        ^
  </PRE>
- then the string they capture is "ab(cd)ef", the contents of the top level
+ the string they capture is "ab(cd)ef", the contents of the top level
  parentheses. If there are more than 15 capturing parentheses in a pattern, PCRE
  has to obtain extra memory to store data during a recursion, which it does by
  using <B>pcre_malloc</B>, freeing it via <B>pcre_free</B> afterwards. If no

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