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    Command:

    pcreunicode

    
    
    

    UTF-8, UTF-16, UTF-32, AND UNICODE PROPERTY SUPPORT

    
           As well as UTF-8 support, PCRE also supports UTF-16 (from release 8.30)
           and UTF-32 (from release 8.32), by means of two  additional  libraries.
           They can be built as well as, or instead of, the 8-bit library.
    
    
    

    UTF-8 SUPPORT

    
           In  order  process  UTF-8  strings, you must build PCRE's 8-bit library
           with UTF support, and, in addition, you must call  pcre_compile()  with
           the  PCRE_UTF8 option flag, or the pattern must start with the sequence
           (*UTF8) or (*UTF). When either of these is the case, both  the  pattern
           and  any  subject  strings  that  are matched against it are treated as
           UTF-8 strings instead of strings of individual 1-byte characters.
    
    
    

    UTF-16 AND UTF-32 SUPPORT

    
           In order process UTF-16 or UTF-32 strings, you must build PCRE's 16-bit
           or  32-bit  library  with  UTF support, and, in addition, you must call
           pcre16_compile() or pcre32_compile() with the PCRE_UTF16 or  PCRE_UTF32
           option flag, as appropriate. Alternatively, the pattern must start with
           the sequence (*UTF16), (*UTF32), as appropriate, or (*UTF),  which  can
           be used with either library. When UTF mode is set, both the pattern and
           any subject strings that are matched against it are treated  as  UTF-16
           or  UTF-32  strings  instead  of strings of individual 16-bit or 32-bit
           characters.
    
    
    

    UTF SUPPORT OVERHEAD

    
           If you compile PCRE with UTF support, but do not use it  at  run  time,
           the  library will be a bit bigger, but the additional run time overhead
           is limited to  testing  the  PCRE_UTF[8|16|32]  flag  occasionally,  so
           should not be very big.
    
    
    

    UNICODE PROPERTY SUPPORT

    
           If PCRE is built with Unicode character property support (which implies
           UTF support), the escape sequences \p{..}, \P{..}, and \X can be  used.
           The  available properties that can be tested are limited to the general
           category properties such as Lu for an upper case letter  or  Nd  for  a
           decimal number, the Unicode script names such as Arabic or Han, and the
           derived properties Any and L&. Full lists is given in  the  pcrepattern
           and  pcresyntax  documentation. Only the short names for properties are
           supported. For example, \p{L}  matches  a  letter.  Its  Perl  synonym,
           \p{Letter},  is  not  supported.  Furthermore, in Perl, many properties
           may optionally be prefixed by "Is", for compatibility  with  Perl  5.6.
           PCRE does not support this.
    
       Validity of UTF-8 strings
    
           When  you  set  the PCRE_UTF8 flag, the byte strings passed as patterns
           and subjects are (by default) checked for validity on entry to the rel-
           other  words,  the  whole  surrogate  thing is a fudge for UTF-16 which
           unfortunately messes up UTF-8 and UTF-32.)
    
           If an invalid UTF-8 string is passed to PCRE, an error return is given.
           At  compile  time, the only additional information is the offset to the
           first byte of the failing character. The run-time functions pcre_exec()
           and  pcre_dfa_exec() also pass back this information, as well as a more
           detailed reason code if the caller has provided memory in which  to  do
           this.
    
           In  some  situations, you may already know that your strings are valid,
           and therefore want to skip these checks in  order  to  improve  perfor-
           mance,  for  example in the case of a long subject string that is being
           scanned repeatedly.  If you set the PCRE_NO_UTF8_CHECK flag at  compile
           time  or  at  run  time, PCRE assumes that the pattern or subject it is
           given (respectively) contains only valid UTF-8 codes. In this case,  it
           does not diagnose an invalid UTF-8 string.
    
           Note  that  passing  PCRE_NO_UTF8_CHECK to pcre_compile() just disables
           the check for the pattern; it does not also apply to  subject  strings.
           If  you  want  to  disable the check for a subject string you must pass
           this option to pcre_exec() or pcre_dfa_exec().
    
           If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, the
           result is undefined and your program may crash.
    
       Validity of UTF-16 strings
    
           When you set the PCRE_UTF16 flag, the strings of 16-bit data units that
           are passed as patterns and subjects are (by default) checked for valid-
           ity  on entry to the relevant functions. Values other than those in the
           surrogate range U+D800 to U+DFFF are independent code points. Values in
           the surrogate range must be used in pairs in the correct manner.
    
           If  an  invalid  UTF-16  string  is  passed to PCRE, an error return is
           given. At compile time, the only additional information is  the  offset
           to the first data unit of the failing character. The run-time functions
           pcre16_exec() and pcre16_dfa_exec() also pass back this information, as
           well  as  a more detailed reason code if the caller has provided memory
           in which to do this.
    
           In some situations, you may already know that your strings  are  valid,
           and  therefore  want  to  skip these checks in order to improve perfor-
           mance. If you set the PCRE_NO_UTF16_CHECK flag at compile  time  or  at
           run time, PCRE assumes that the pattern or subject it is given (respec-
           tively) contains only valid UTF-16 sequences. In this case, it does not
           diagnose  an  invalid  UTF-16 string.  However, if an invalid string is
           passed, the result is undefined.
    
       Validity of UTF-32 strings
    
           When you set the PCRE_UTF32 flag, the strings of 32-bit data units that
           mance.  If  you  set the PCRE_NO_UTF32_CHECK flag at compile time or at
           run time, PCRE assumes that the pattern or subject it is given (respec-
           tively) contains only valid UTF-32 sequences. In this case, it does not
           diagnose an invalid UTF-32 string.  However, if an  invalid  string  is
           passed, the result is undefined.
    
       General comments about UTF modes
    
           1.  Codepoints  less  than  256  can be specified in patterns by either
           braced or unbraced hexadecimal escape sequences (for example, \x{b3} or
           \xb3). Larger values have to use braced sequences.
    
           2.  Octal  numbers  up  to  \777 are recognized, and in UTF-8 mode they
           match two-byte characters for values greater than \177.
    
           3. Repeat quantifiers apply to complete UTF characters, not to individ-
           ual data units, for example: \x{100}{3}.
    
           4.  The dot metacharacter matches one UTF character instead of a single
           data unit.
    
           5. The escape sequence \C can be used to match a single byte  in  UTF-8
           mode,  or  a single 16-bit data unit in UTF-16 mode, or a single 32-bit
           data unit in UTF-32 mode, but its use can lead to some strange  effects
           because  it  breaks up multi-unit characters (see the description of \C
           in the pcrepattern documentation). The use of \C is  not  supported  in
           the  alternative  matching  function  pcre[16|32]_dfa_exec(), nor is it
           supported in UTF mode by the JIT optimization of pcre[16|32]_exec(). If
           JIT  optimization  is  requested for a UTF pattern that contains \C, it
           will not succeed, and so the matching will be carried out by the normal
           interpretive function.
    
           6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
           test characters of any code value, but, by default, the characters that
           PCRE  recognizes  as digits, spaces, or word characters remain the same
           set as in non-UTF mode, all with values less  than  256.  This  remains
           true  even  when  PCRE  is  built  to include Unicode property support,
           because to do otherwise would slow down PCRE in many common cases. Note
           in  particular that this applies to \b and \B, because they are defined
           in terms of \w and \W. If you really want to test for a wider sense of,
           say,  "digit",  you  can  use  explicit  Unicode property tests such as
           \p{Nd}. Alternatively, if you set the PCRE_UCP option, the way that the
           character  escapes  work is changed so that Unicode properties are used
           to determine which characters match. There are more details in the sec-
           tion on generic character types in the pcrepattern documentation.
    
           7.  Similarly,  characters that match the POSIX named character classes
           are all low-valued characters, unless the PCRE_UCP option is set.
    
           8. However, the horizontal and vertical white  space  matching  escapes
           (\h,  \H,  \v, and \V) do match all the appropriate Unicode characters,
           whether or not PCRE_UCP is set.
    
    
    

    REVISION

    
           Last updated: 27 February 2013
           Copyright (c) 1997-2013 University of Cambridge.
    
    
    

    PCRE 8.33 27 February 2013 PCREUNICODE(3)

    
    
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