From: Jarkko Hietaniemi Date: Wed, 14 Nov 2001 22:30:59 +0000 (+0000) Subject: Add perlunintro (formerly known as perlunitut); regen toc. X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=ba62762e535f4b26bec252f67a5dcfb2a28c8b16;p=p5sagit%2Fp5-mst-13.2.git Add perlunintro (formerly known as perlunitut); regen toc. p4raw-id: //depot/perl@13010 --- diff --git a/MANIFEST b/MANIFEST index cf37116..d6732af 100644 --- a/MANIFEST +++ b/MANIFEST @@ -1890,6 +1890,7 @@ pod/perltodo.pod Todo list explained pod/perltooc.pod Tom's object-oriented tutorial (more on class data) pod/perltoot.pod Tom's object-oriented tutorial pod/perltrap.pod Trap info +pod/perlunintro.pod Unicode introduction pod/perlunicode.pod Unicode support info pod/perlutil.pod Accompanying utilities explained pod/perlvar.pod Variable info diff --git a/pod/buildtoc.PL b/pod/buildtoc.PL index 313a3ef..7502e05 100644 --- a/pod/buildtoc.PL +++ b/pod/buildtoc.PL @@ -145,6 +145,7 @@ if (-d "pod") { perlport perllocale + perlunintro perlunicode perlebcdic @@ -289,6 +290,7 @@ sub getpods { return if $file eq '../lib/Pod/Functions.pm'; # Used only by pod itself return if $file =~ m!lib/Attribute/Handlers/demo/!; return if $file =~ m!lib/Net/FTP/.+\.pm!; # Hi, Graham! :-) + return if $file =~ m!lib/Math/BigInt/t/!; die "tut $name" if $file =~ /TUT/; unless (open (F, "< $_\0")) { diff --git a/pod/perl.pod b/pod/perl.pod index 83c3097..0aa17d9 100644 --- a/pod/perl.pod +++ b/pod/perl.pod @@ -85,7 +85,8 @@ For ease of access, the Perl manual has been split up into several sections. perlport Perl portability guide perllocale Perl locale support - perlunicode Perl unicode support + perlunintro Perl Unicode introduction + perlunicode Perl Unicode support perlebcdic Considerations for running Perl on EBCDIC platforms perlsec Perl security diff --git a/pod/perltoc.pod b/pod/perltoc.pod index 0d2e613..7edde52 100644 --- a/pod/perltoc.pod +++ b/pod/perltoc.pod @@ -536,11 +536,11 @@ more elaborate constructs =over 4 -=item Declaration of a ARRAY OF ARRAYS +=item Declaration of an ARRAY OF ARRAYS -=item Generation of a ARRAY OF ARRAYS +=item Generation of an ARRAY OF ARRAYS -=item Access and Printing of a ARRAY OF ARRAYS +=item Access and Printing of an ARRAY OF ARRAYS =back @@ -560,11 +560,11 @@ more elaborate constructs =over 4 -=item Declaration of a ARRAY OF HASHES +=item Declaration of an ARRAY OF HASHES -=item Generation of a ARRAY OF HASHES +=item Generation of an ARRAY OF HASHES -=item Access and Printing of a ARRAY OF HASHES +=item Access and Printing of an ARRAY OF HASHES =back @@ -1971,20 +1971,21 @@ http://testers.cpan.org/ -I FILEHANDLE, -I EXPR, -I, alarm SECONDS, alarm, binmode FILEHANDLE, chmod LIST, chown LIST, chroot FILENAME, chroot, crypt PLAINTEXT,SALT, dbmclose HASH, dbmopen HASH,DBNAME,MODE, dump LABEL, exec -LIST, fcntl FILEHANDLE,FUNCTION,SCALAR, flock FILEHANDLE,OPERATION, fork, -getlogin, getpgrp PID, getppid, getpriority WHICH,WHO, getpwnam NAME, -getgrnam NAME, getnetbyname NAME, getpwuid UID, getgrgid GID, getnetbyaddr -ADDR,ADDRTYPE, getprotobynumber NUMBER, getservbyport PORT,PROTO, getpwent, -getgrent, gethostent, getnetent, getprotoent, getservent, setpwent, -setgrent, sethostent STAYOPEN, setnetent STAYOPEN, setprotoent STAYOPEN, -setservent STAYOPEN, endpwent, endgrent, endhostent, endnetent, -endprotoent, endservent, exit EXPR, exit, getsockopt SOCKET,LEVEL,OPTNAME, -glob EXPR, glob, ioctl FILEHANDLE,FUNCTION,SCALAR, kill SIGNAL, LIST, link -OLDFILE,NEWFILE, lstat FILEHANDLE, lstat EXPR, lstat, msgctl ID,CMD,ARG, -msgget KEY,FLAGS, msgsnd ID,MSG,FLAGS, msgrcv ID,VAR,SIZE,TYPE,FLAGS, open -FILEHANDLE,EXPR, open FILEHANDLE, pipe READHANDLE,WRITEHANDLE, readlink -EXPR, readlink, select RBITS,WBITS,EBITS,TIMEOUT, semctl ID,SEMNUM,CMD,ARG, -semget KEY,NSEMS,FLAGS, semop KEY,OPSTRING, setgrent, setpgrp PID,PGRP, +LIST, exit EXPR, exit, fcntl FILEHANDLE,FUNCTION,SCALAR, flock +FILEHANDLE,OPERATION, fork, getlogin, getpgrp PID, getppid, getpriority +WHICH,WHO, getpwnam NAME, getgrnam NAME, getnetbyname NAME, getpwuid UID, +getgrgid GID, getnetbyaddr ADDR,ADDRTYPE, getprotobynumber NUMBER, +getservbyport PORT,PROTO, getpwent, getgrent, gethostent, getnetent, +getprotoent, getservent, setpwent, setgrent, sethostent STAYOPEN, setnetent +STAYOPEN, setprotoent STAYOPEN, setservent STAYOPEN, endpwent, endgrent, +endhostent, endnetent, endprotoent, endservent, getsockopt +SOCKET,LEVEL,OPTNAME, glob EXPR, glob, ioctl FILEHANDLE,FUNCTION,SCALAR, +kill SIGNAL, LIST, link OLDFILE,NEWFILE, lstat FILEHANDLE, lstat EXPR, +lstat, msgctl ID,CMD,ARG, msgget KEY,FLAGS, msgsnd ID,MSG,FLAGS, msgrcv +ID,VAR,SIZE,TYPE,FLAGS, open FILEHANDLE,EXPR, open FILEHANDLE, pipe +READHANDLE,WRITEHANDLE, readlink EXPR, readlink, select +RBITS,WBITS,EBITS,TIMEOUT, semctl ID,SEMNUM,CMD,ARG, semget +KEY,NSEMS,FLAGS, semop KEY,OPSTRING, setgrent, setpgrp PID,PGRP, setpriority WHICH,WHO,PRIORITY, setpwent, setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL, shmctl ID,CMD,ARG, shmget KEY,SIZE,FLAGS, shmread ID,VAR,POS,SIZE, shmwrite ID,STRING,POS,SIZE, sockatmark SOCKET, @@ -2109,6 +2110,56 @@ LC_NUMERIC, LC_TIME, LANG =back +=head2 perlunintro - Perl Unicode introduction + +=over 4 + +=item DESCRIPTION + +=over 4 + +=item Unicode + +=item Perl's Unicode Support + +=item Perl's Unicode Model + +=item Creating Unicode + +=item Handling Unicode + +=item Legacy Encodings + +=item Unicode I/O + +=item Special Cases + +=item Advanced Topics + +=item Miscellaneous + +=item Questions With Answers + +Will My Old Scripts Break?, How Do I Make My Scripts Work With Unicode?, +How Do I Know Whether My String Is In Unicode?, How Do I Detect Invalid +UTF-8?, How Do I Convert Data Into UTF-8? Or Vice Versa?, How Do I Display +Unicode? How Do I Input Unicode?, How Does Unicode Work With Traditional +Locales? + +=item Hexadecimal Notation + +=item Further Resources + +=back + +=item SEE ALSO + +=item ACKNOWLEDGEMENTS + +=item AUTHOR, COPYRIGHT, AND LICENSE + +=back + =head2 perlunicode - Unicode support in Perl =over 4 @@ -2138,6 +2189,19 @@ to enable UTF-8/UTF-EBCDIC in scripts =item UNICODE REGULAR EXPRESSION SUPPORT LEVEL +=over 4 + +=item Unicode Encodings + +UTF-8, UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks), +UTF-32, UTF-32BE, UTF32-LE, UCS-2, UCS-4, UTF-7 + +=item Security Implications of Malformed UTF-8 + +=item Unicode in Perl on EBCDIC + +=back + =item SEE ALSO =back @@ -7412,7 +7476,7 @@ semantics =back =head2 charnames - define character names for C<\N{named}> string literal -escape. +escapes. =over 4 @@ -7422,6 +7486,8 @@ escape. =item CUSTOM TRANSLATORS +=item charnames::viacode(code) + =item BUGS =back @@ -7805,6 +7871,18 @@ utf8::encode($string), $flag = utf8::decode($string) =back +=head2 vmsish - Perl pragma to control VMS-specific language features + +=over 4 + +=item SYNOPSIS + +=item DESCRIPTION + +C, C, C, C + +=back + =head2 warnings - Perl pragma to control optional warnings =over 4 @@ -8427,8 +8505,8 @@ TIMEDIFF, [ STYLE, [ FORMAT ] ] ) =item Optional Exports clearcache ( COUNT ), clearallcache ( ), cmpthese ( COUT, CODEHASHREF, [ -STYLE ] ), cmpthese ( RESULTSHASHREF ), countit(TIME, CODE), disablecache ( -), enablecache ( ), timesum ( T1, T2 ) +STYLE ] ), cmpthese ( RESULTSHASHREF, [ STYLE ] ), countit(TIME, CODE), +disablecache ( ), enablecache ( ), timesum ( T1, T2 ) =back @@ -9909,8 +9987,8 @@ Fixed length 32-bit encodings, Multi-byte encodings, "Escape" encodings =item Encoding Names -The MIME name as defined in IETF RFC-XXXX, The name in the IANA registry, -The name used by the organization that defined it +The MIME name as defined in IETF RFCs, The name in the IANA registry, The +name used by the organization that defined it =back @@ -13632,7 +13710,7 @@ functions =over 4 -=item How do I download files from a FTP server ? +=item How do I download files from an FTP server ? =item How do I transfer files in binary mode ? @@ -13645,13 +13723,13 @@ functions =item Can I do a reget operation like the ftp command ? -=item How do I get a directory listing from a FTP server ? +=item How do I get a directory listing from an FTP server ? -=item Changeing directory to "" does not fail ? +=item Changing directory to "" does not fail ? =item I am behind a SOCKS firewall, but the Firewall option does not work ? -=item I am behind a FTP proxy firewall, but cannot access machines outside +=item I am behind an FTP proxy firewall, but cannot access machines outside ? =item My ftp proxy firewall does not listen on port 21 @@ -15429,6 +15507,8 @@ C =item BUGS +=item LIMITATION + =item COPYRIGHT =back @@ -16361,8 +16441,8 @@ function =item DESCRIPTION -isa ( TYPE ), can ( METHOD ), VERSION ( [ REQUIRE ] ), UNIVERSAL::isa ( -VAL, TYPE ), UNIVERSAL::can ( VAL, METHOD ) +$obj->isa( TYPE ), CLASS->isa( TYPE ), isa( VAL, TYPE ), $obj->can( METHOD +), CLASS->can( METHOD ), can( VAL, METHOD ), VERSION ( [ REQUIRE ] ) =back @@ -16384,10 +16464,14 @@ undefChar, katakana_before_hiragana, upper_before_lower =item Other methods -C<@sorted = $UCA-Esort(@not_sorted)>, C<$result = $UCA-Ecmp($a, -$b)>, C<$sortKey = $UCA-EgetSortKey($string)>, C<$position = -$UCA-Eindex($string, $substring)>, C<($position, $length) = -$UCA-Eindex($string, $substring)> +C<@sorted = $Collator-Esort(@not_sorted)>, C<$result = +$Collator-Ecmp($a, $b)>, C<$result = $Collator-Eeq($a, $b)>, +C<$result = $Collator-Ene($a, $b)>, C<$result = $Collator-Elt($a, +$b)>, C<$result = $Collator-Ele($a, $b)>, C<$result = +$Collator-Egt($a, $b)>, C<$result = $Collator-Ege($a, $b)>, +C<$sortKey = $Collator-EgetSortKey($string)>, C<$position = +$Collator-Eindex($string, $substring)>, C<($position, $length) = +$Collator-Eindex($string, $substring)> =item EXPORT @@ -16399,8 +16483,7 @@ $UCA-Eindex($string, $substring)> =item SEE ALSO -L, L, Unicode Collation -Algorithm - Unicode TR #10 +Unicode Collation Algorithm - Unicode TR #10, L =back diff --git a/pod/perlunintro.pod b/pod/perlunintro.pod new file mode 100644 index 0000000..bb30c0b --- /dev/null +++ b/pod/perlunintro.pod @@ -0,0 +1,689 @@ +=head1 NAME + +perlunintro - Perl Unicode introduction + +=head1 DESCRIPTION + +This document gives a general idea of Unicode and how to use Unicode +in Perl. + +=head2 Unicode + +Unicode is a character set standard with plans to cover all of the +writing systems of the world, plus many other symbols. + +Unicode and ISO/IEC 10646 are coordinated standards that provide code +points for the characters in almost all modern character set standards, +covering more than 30 writing systems and hundreds of languages, +including all commercially important modern languages. All characters +in the largest Chinese, Japanese, and Korean dictionaries are also +encoded. The standards will eventually cover almost all characters in +more than 250 writing systems and thousands of languages. + +A Unicode I is an abstract entity. It is not bound to any +particular integer width, and especially not to the C language C. +Unicode is language neutral and display neutral: it doesn't encode the +language of the text, and it doesn't define fonts or other graphical +layout details. Unicode operates on characters and on text built from +those characters. + +Unicode defines characters like C or C, and then unique numbers for those, hexadecimal +0x0041 or 0x03B1 for those particular characters. Such unique +numbers are called I. + +The Unicode standard prefers using hexadecimal notation for the code +points. (In case this notation, numbers like 0x0041, is unfamiliar to +you, take a peek at a later section, L.) +The Unicode standard uses the notation C, +which gives the hexadecimal code point, and the normative name of +the character. + +Unicode also defines various I for the characters, like +"uppercase" or "lowercase", "decimal digit", or "punctuation": +these properties are independent of the names of the characters. +Furthermore, various operations on the characters like uppercasing, +lowercasing, and collating (sorting), are defined. + +A Unicode character consists either of a single code point, or a +I (like C), followed by one or +more I (like C). This sequence of +a base character and modifiers is called a I. + +Whether to call these combining character sequences, as a whole, +"characters" depends on your point of view. If you are a programmer, you +probably would tend towards seeing each element in the sequences as one +unit, one "character", but from the user viewpoint, the sequence as a +whole is probably considered one "character", since that's probably what +it looks like in the context of the user's language. + +With this "as a whole" view of characters, the number of characters is +open-ended. But in the programmer's "one unit is one character" point of +view, the concept of "characters" is more deterministic, and so we take +that point of view in this document: one "character" is one Unicode +code point, be it a base character or a combining character. + +For some of the combinations there are I characters, +for example C is defined as +a single code point. These precomposed characters are, however, +often available only for some combinations, and mainly they are +meant to support round-trip conversions between Unicode and legacy +standards (like the ISO 8859), and in general case the composing +method is more extensible. To support conversion between the +different compositions of the characters, various I are also defined. + +Because of backward compatibility with legacy encodings, the "a unique +number for every character" breaks down a bit: "at least one number +for every character" is closer to truth. (This happens when the same +character has been encoded in several legacy encodings.) The converse +is also not true: not every code point has an assigned character. +Firstly, there are unallocated code points within otherwise used +blocks. Secondly, there are special Unicode control characters that +do not represent true characters. + +A common myth about Unicode is that it would be "16-bit", that is, +0x10000 (or 65536) characters from 0x0000 to 0xFFFF. B +Since Unicode 2.0 Unicode has been defined all the way up to 21 bits +(0x10FFFF), and since 3.1 characters have been defined beyond 0xFFFF. +The first 0x10000 characters are called the I, or the I (BMP). With the Unicode 3.1, 17 planes in all are +defined (but nowhere near full of defined characters yet). + +Another myth is that the 256-character blocks have something to do +with languages: a block per language. B +The division into the blocks exists but it is almost completely +accidental, an artifact of how the characters have been historically +allocated. Instead, there is a concept called I, which may +be more useful: there is C script, C script, and so on. +Scripts usually span several parts of several blocks. For further +information see L. + +The Unicode code points are just abstract numbers. To input and +output these abstract numbers, the numbers must be I somehow. +Unicode defines several I, of which I +is perhaps the most popular. UTF-8 is a variable length encoding that +encodes Unicode characters as 1 to 6 bytes (only 4 with the currently +defined characters). Other encodings are UTF-16 and UTF-32 and their +big and little endian variants (UTF-8 is byteorder independent). +The ISO/IEC 10646 defines the UCS-2 and UCS-4 encoding forms. + +For more information about encodings, for example to learn what +I and I (BOMs) are, see L. + +=head2 Perl's Unicode Support + +Starting from Perl 5.6.0, Perl has had the capability of handling +Unicode natively. The first recommended release for serious Unicode +work is Perl 5.8.0, however. The maintenance release 5.6.1 fixed many +of the problems of the initial implementation of Unicode, but for +example regular expressions didn't really work with Unicode. + +B is no longer +necessary.> In earlier releases the C pragma was used to declare +that operations in the current block or file would be Unicode-aware. +This model was found to be wrong, or at least clumsy: the Unicodeness +is now carried with the data, not attached to the operations. (There +is one remaining case where an explicit C is needed: if your +Perl script is in UTF-8, you can use UTF-8 in your variable and +subroutine names, and in your string and regular expression literals, +by saying C. This is not the default because that would +break existing scripts having legacy 8-bit data in them.) + +=head2 Perl's Unicode Model + +Perl supports both the old, pre-5.6, model of strings of eight-bit +native bytes, and strings of Unicode characters. The principle is +that Perl tries to keep its data as eight-bit bytes for as long as +possible, but as soon as Unicodeness cannot be avoided, the data is +transparently upgraded to Unicode. + +The internal encoding of Unicode in Perl is UTF-8. The internal +encoding is normally hidden, however, and one need not and should not +worry about the internal encoding at all: it is all just characters. + +Perl 5.8.0 will also support Unicode on EBCDIC platforms. There the +support is somewhat harder to implement since additional conversions +are needed at every step. Because of these difficulties the Unicode +support won't be quite as full as in other, mainly ASCII-based, +platforms (the Unicode support will be better than in the 5.6 series, +which didn't work much at all for EBCDIC platform). On EBCDIC +platforms the internal encoding form used is UTF-EBCDIC. + +=head2 Creating Unicode + +To create Unicode literals, use the C<\x{...}> notation in +doublequoted strings: + + my $smiley = "\x{263a}"; + +Similarly for regular expression literals + + $smiley =~ /\x{263a}/; + +At run-time you can use C: + + my $hebrew_alef = chr(0x05d0); + +(See L for how to find all these numeric codes.) + +Naturally, C will do the reverse: turn a character to a code point. + +Note that C<\x..>, C<\x{..}> and C for arguments less than +0x100 (decimal 256) will generate an eight-bit character for backward +compatibility with older Perls. For arguments of 0x100 or more, +Unicode will always be produced. If you want UTF-8 always, use +C instead of C<\x..>, C<\x{..}>, or C. + +You can also use the C pragma to invoke characters +by name in doublequoted strings: + + use charnames ':full'; + my $arabic_alef = "\N{ARABIC LETTER ALEF}"; + +And, as mentioned above, you can also C numbers into Unicode +characters: + + my $georgian_an = pack("U", 0x10a0); + +=head2 Handling Unicode + +Handling Unicode is for the most part transparent: just use the +strings as usual. Functions like C, C, and +C will work on the Unicode characters; regular expressions +will work on the Unicode characters (see L and L). + +Note that Perl does B consider combining character sequences +to be characters, such for example + + use charnames ':full'; + print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), "\n"; + +will print 2, not 1. The only exception is that regular expressions +have C<\X> for matching a combining character sequence. + +When life is not quite so transparent is working with legacy +encodings, and I/O, and certain special cases. + +=head2 Legacy Encodings + +When you combine legacy data and Unicode the legacy data needs +to be upgraded to Unicode. Normally ISO 8859-1 (or EBCDIC, if +applicable) is assumed. You can override this assumption by +using the C pragma, for example + + use encoding 'latin2'; # ISO 8859-2 + +in which case literals (string or regular expression) and chr/ord +in your whole script are assumed to produce Unicode characters from +ISO 8859-2 code points. Note that the matching for the encoding +names is forgiving: instead of C you could have said +C, or C, and so forth. With just + + use encoding; + +first the environment variable C will be consulted, +and if that doesn't exist, ISO 8859-1 (Latin 1) will be assumed. + +The C module knows about many encodings and it has interfaces +for doing conversions between those encodings: + + use Encode 'from_to'; + from_to($data, "iso-8859-3", "utf-8"); # from legacy to utf-8 + +=head2 Unicode I/O + +Normally writing out Unicode data + + print chr(0x100), "\n"; + +will print out the raw UTF-8 bytes. + +But reading in correctly formed UTF-8 data will not magically turn +the data into Unicode in Perl's eyes. + +You can use either the C<':utf8'> I/O discipline when opening files + + open(my $fh,'<:utf8', 'anything'); + my $line_of_utf8 = <$fh>; + +The I/O disciplines can also be specified more flexibly with +the C pragma; see L: + + use open ':utf8'; # input and output will be UTF-8 + open X, ">utf8"; + print X chr(0x100), "\n"; # this would have been UTF-8 without the pragma + close X; + open Y, "); # this should print 0x100 + close Y; + +With the C pragma you can use the C<:locale> discipline + + $ENV{LANG} = 'ru_RU.KOI8-R'; + # the :locale will probe the locale environment variables like LANG + use open OUT => ':locale'; # russki parusski + open(O, ">koi8"); + print O chr(0x430); # Unicode CYRILLIC SMALL LETTER A = KOI8-R 0xc1 + close O; + open(I, "), "\n"; # this should print 0xc1 + close I; + +or you can also use the C<':encoding(...)'> discipline + + open(my $epic,'<:encoding(iso-8859-7)','iliad.greek'); + my $line_of_iliad = <$epic>; + +Both of these methods install a transparent filter on the I/O stream that +will convert data from the specified encoding when it is read in from the +stream. In the first example the F file is assumed to be UTF-8 +encoded Unicode, in the second example the F file is assumed +to be ISO-8858-7 encoded Greek, but the lines read in will be in both +cases Unicode. + +The L pragma affects all the C calls after the pragma by +setting default disciplines. If you want to affect only certain +streams, use explicit disciplines directly in the C call. + +You can switch encodings on an already opened stream by using +C, see L. + +The C<:locale> does not currently work with C and +C, only with the C pragma. The C<:utf8> and +C<:encoding(...)> do work with all of C, C, +and the C pragma. + +Similarly, you may use these I/O disciplines on input streams to +automatically convert data from the specified encoding when it is +written to the stream. + + open(my $unicode, '<:utf8', 'japanese.uni'); + open(my $nihongo, '>:encoding(iso2022-jp)', 'japanese.jp'); + while (<$unicode>) { print $nihongo } + +The naming of encodings, both by the C and by the C +pragma, is similarly understanding as with the C pragma: +C and C will both be understood. + +Common encodings recognized by ISO, MIME, IANA, and various other +standardisation organisations are recognised, for a more detailed +list see L. + +C reads characters and returns the number of characters. +C and C operate on byte counts, as do C +and C. + +Notice that because of the default behaviour "input is not UTF-8" +it is easy to mistakenly write code that keeps on expanding a file +by repeatedly encoding it in UTF-8: + + # BAD CODE WARNING + open F, "file"; + local $/; # read in the whole file + $t = ; + close F; + open F, ">:utf8", "file"; + print F $t; + close F; + +If you run this code twice, the contents of the F will be twice +UTF-8 encoded. A C would have avoided the bug. + +=head2 Special Cases + +=over 4 + +=item * + +Bit Complement Operator ~ And vec() + +The bit complement operator C<~> will produce surprising results if +used on strings containing Unicode characters. The results are +consistent with the internal UTF-8 encoding of the characters, but not +with much else. So don't do that. Similarly for vec(): you will be +operating on the UTF-8 bit patterns of the Unicode characters, not on +the bytes, which is very probably not what you want. + +=item * + +Peeking At UTF-8 + +One way of peeking inside the internal encoding of Unicode characters +is to use C to get the bytes, or C +to display the bytes: + + # this will print c4 80 for the UTF-8 bytes 0xc4 0x80 + print join(" ", unpack("H*", pack("U", 0x100))), "\n"; + +Yet another way would be to use the Devel::Peek module: + + perl -MDevel::Peek -e 'Dump(chr(0x100))' + +That will show the UTF8 flag in FLAGS and both the UTF-8 bytes +and Unicode characters in PV. See also later in this document +the discussion about the C function of the C module. + +=back + +=head2 Advanced Topics + +=over 4 + +=item * + +String Equivalence + +The question of string equivalence turns somewhat complicated +in Unicode: what do you mean by equal? + + Is C equal to + C? + +The short answer is that by default Perl compares equivalence +(C, C) based only on code points of the characters. +In the above case, no (because 0x00C1 != 0x0041). But sometimes any +CAPITAL LETTER As being considered equal, or even any As of any case, +would be desirable. + +The long answer is that you need to consider character normalization +and casing issues: see L, and Unicode Technical +Reports #15 and #21, I and I, http://www.unicode.org/unicode/reports/tr15/ +http://www.unicode.org/unicode/reports/tr21/ + +As of Perl 5.8.0, the's regular expression case-ignoring matching +implements only 1:1 semantics: one character matches one character. +In I both 1:N and N:1 matches are defined. + +=item * + +String Collation + +People like to see their strings nicely sorted, or as Unicode +parlance goes, collated. But again, what do you mean by collate? + + Does C come before or after + C? + +The short answer is that by default Perl compares strings (C, +C, C, C, C) based only on the code points of the +characters. In the above case, after, since 0x00C1 > 0x00C0. + +The long answer is that "it depends", and a good answer cannot be +given without knowing (at the very least) the language context. +See L, and I +http://www.unicode.org/unicode/reports/tr10/ + +=back + +=head2 Miscellaneous + +=over 4 + +=item * + +Character Ranges + +Character ranges in regular expression character classes (C) +and in the C (also known as C) operator are not magically +Unicode-aware. What this means that C<[a-z]> will not magically start +to mean "all alphabetic letters" (not that it does mean that even for +8-bit characters, you should be using C for that). + +For specifying things like that in regular expressions you can use the +various Unicode properties, C<\pL> in this particular case. You can +use Unicode code points as the end points of character ranges, but +that means that particular code point range, nothing more. For +further information, see L. + +=item * + +String-To-Number Conversions + +Unicode does define several other decimal (and numeric) characters +than just the familiar 0 to 9, such as the Arabic and Indic digits. +Perl does not support string-to-number conversion for digits other +than the 0 to 9 (and a to f for hexadecimal). + +=back + +=head2 Questions With Answers + +=over 4 + +=item Will My Old Scripts Break? + +Very probably not. Unless you are generating Unicode characters +somehow, any old behaviour should be preserved. About the only +behaviour that has changed and which could start generating Unicode +is the old behaviour of C where supplying an argument more +than 255 produced a character modulo 255 (for example, C +was equal to C). + +=item How Do I Make My Scripts Work With Unicode? + +Very little work should be needed since nothing changes until you +somehow generate Unicode data. The greatest trick will be getting +input as Unicode, and for that see the earlier I/O discussion. + +=item How Do I Know Whether My String Is In Unicode? + +You shouldn't care. No, you really shouldn't. If you have +to care (beyond the cases described above), it means that we +didn't get the transparency of Unicode quite right. + +Okay, if you insist: + + use Encode 'is_utf8'; + print is_utf8($string) ? 1 : 0, "\n"; + +But note that this doesn't mean that any of the characters in the +string are necessary UTF-8 encoded, or that any of the characters have +code points greater than 0xFF (255) or even 0x80 (128), or that the +string has any characters at all. All the C does is to +return the value of the internal "utf8ness" flag attached to the +$string. If the flag is on, characters added to that string will be +automatically upgraded to UTF-8 (and even then only if they really +need to be upgraded, that is, if their code point is greater than 0xFF). + +Sometimes you might really need to know the byte length of a string +instead of the character length. For that use the C pragma +and its only defined function C: + + my $unicode = chr(0x100); + print length($unicode), "\n"; # will print 1 + use bytes; + print length($unicode), "\n"; # will print 2 (the 0xC4 0x80 of the UTF-8) + +=item How Do I Detect Invalid UTF-8? + +Either + + use Encode 'encode_utf8'; + if (encode_utf8($string)) { + # valid + } else { + # invalid + } + +or + + use warnings; + @chars = unpack("U0U*", "\xFF"); # will warn + +The warning will be C. The "U0" means "expect strictly UTF-8 encoded Unicode". +Without that the C would accept also data like +C). + +=item How Do I Convert Data Into UTF-8? Or Vice Versa? + +This probably isn't as useful (or simple) as you might think. +Also, normally you shouldn't need to. + +In one sense what you are asking doesn't make much sense: UTF-8 is +(intended as an) Unicode encoding, so converting "data" into UTF-8 +isn't meaningful unless you know in what character set and encoding +the binary data is in, and in this case you can use C. + + use Encode 'from_to'; + from_to($data, "iso-8859-1", "utf-8"); # from latin-1 to utf-8 + +If you have ASCII (really 7-bit US-ASCII), you already have valid +UTF-8, the lowest 128 characters of UTF-8 encoded Unicode and US-ASCII +are equivalent. + +If you have Latin-1 (or want Latin-1), you can just use pack/unpack: + + $latin1 = pack("C*", unpack("U*", $utf8)); + $utf8 = pack("U*", unpack("C*", $latin1)); + +(The same works for EBCDIC.) + +If you have a sequence of bytes you B is valid UTF-8, +but Perl doesn't know it yet, you can make Perl a believer, too: + + use Encode 'decode_utf8'; + $utf8 = decode_utf8($bytes); + +You can convert well-formed UTF-8 to a sequence of bytes, but if +you just want to convert random binary data into UTF-8, you can't. +Any random collection of bytes isn't well-formed UTF-8. You can +use C for the former, and you can create +well-formed Unicode/UTF-8 data by C. + +=item How Do I Display Unicode? How Do I Input Unicode? + +See http://www.hclrss.demon.co.uk/unicode/ and +http://www.cl.cam.ac.uk/~mgk25/unicode.html + +=item How Does Unicode Work With Traditional Locales? + +In Perl, not very well. Avoid using locales through the C +pragma. Use only one or the other. + +=back + +=head2 Hexadecimal Notation + +The Unicode standard prefers using hexadecimal notation because that +shows better the division of Unicode into blocks of 256 characters. +Hexadecimal is also simply shorter than decimal. You can use decimal +notation, too, but learning to use hexadecimal just makes life easier +with the Unicode standard. + +The C<0x> prefix means a hexadecimal number, the digits are 0-9 I +a-f (or A-F, case doesn't matter). Each hexadecimal digit represents +four bits, or half a byte. C will show a +hexadecimal number in decimal, and C will +show a decimal number in hexadecimal. If you have just the +"hexdigits" of a hexadecimal number, you can use the C +function. + + print 0x0009, "\n"; # 9 + print 0x000a, "\n"; # 10 + print 0x000f, "\n"; # 15 + print 0x0010, "\n"; # 16 + print 0x0011, "\n"; # 17 + print 0x0100, "\n"; # 256 + + print 0x0041, "\n"; # 65 + + printf "%x\n", 65; # 41 + printf "%#x\n", 65; # 0x41 + + print hex("41"), "\n"; # 65 + +=head2 Further Resources + +=over 4 + +=item * + +Unicode Consortium + + http://www.unicode.org/ + +=item * + +Unicode FAQ + + http://www.unicode.org/unicode/faq/ + +=item * + +Unicode Glossary + + http://www.unicode.org/glossary/ + +=item * + +Unicode Useful Resources + + http://www.unicode.org/unicode/onlinedat/resources.html + +=item * + +Unicode and Multilingual Support in HTML, Fonts, Web Browsers and Other Applications + + http://www.hclrss.demon.co.uk/unicode/ + +=item * + +UTF-8 and Unicode FAQ for Unix/Linux + + http://www.cl.cam.ac.uk/~mgk25/unicode.html + +=item * + +Legacy Character Sets + + http://www.czyborra.com/ + http://www.eki.ee/letter/ + +=item * + +The Unicode support files live within the Perl installation in the +directory + + $Config{installprivlib}/unicore + +in Perl 5.8.0 or newer, and + + $Config{installprivlib}/unicode + +in the Perl 5.6 series. (The renaming to F was done to +avoid naming conflicts with lib/Unicode in case-insensitive filesystems.) +The main Unicode data file is F (or F in +Perl 5.6.1.) You can find the C<$Config{installprivlib}> by + + perl "-V:installprivlib" + +Note that some of the files have been renamed from the Unicode +standard since the Perl installation tries to live by the "8.3" +filenaming restrictions. The renamings are shown in the +accompanying F file. + +You can explore various information from the Unicode data files using +the C module. + +=back + +=head1 SEE ALSO + +L, L, L, L, L, L, +L, L, L, L + +=head1 ACKNOWLEDGEMENTS + +Thanks to the kind readers of the perl5-porters@perl.org, +perl-unicode@perl.org, linux-utf8@nl.linux.org, and unicore@unicode.org +mailing lists for their valuable feedback. + +=head1 AUTHOR, COPYRIGHT, AND LICENSE + +Copyright 2001 Jarkko Hietaniemi + +This document may be distributed under the same terms as Perl itself.