perlunicook - Online in the Cloud

PROGRAM:

NAME

perlunicook - cookbookish examples of handling Unicode in Perl

DESCRIPTION

This manpage contains short recipes demonstrating how to handle common Unicode operations
in Perl, plus one complete program at the end. Any undeclared variables in individual
recipes are assumed to have a previous appropriate value in them.

EXAMPLES

X 0: Standard preamble
Unless otherwise notes, all examples below require this standard preamble to work
correctly, with the "#!" adjusted to work on your system:

#!/usr/bin/env perl

use utf8; # so literals and identifiers can be in UTF-8
use v5.12; # or later to get "unicode_strings" feature
use strict; # quote strings, declare variables
use warnings; # on by default
use warnings qw(FATAL utf8); # fatalize encoding glitches
use open qw(:std :utf8); # undeclared streams in UTF-8
use charnames qw(:full :short); # unneeded in v5.16

This does make even Unix programmers "binmode" your binary streams, or open them with
":raw", but that's the only way to get at them portably anyway.

WARNING: "use autodie" (pre 2.26) and "use open" do not get along with each other.

X 1: Generic Unicode-savvy filter
Always decompose on the way in, then recompose on the way out.

use Unicode::Normalize;

while (<>) {
$_ = NFD($_); # decompose + reorder canonically
...
} continue {
print NFC($_); # recompose (where possible) + reorder canonically
}

X 2: Fine-tuning Unicode warnings
As of v5.14, Perl distinguishes three subclasses of UTFX8 warnings.

use v5.14; # subwarnings unavailable any earlier
no warnings "nonchar"; # the 66 forbidden non-characters
no warnings "surrogate"; # UTF-16/CESU-8 nonsense
no warnings "non_unicode"; # for codepoints over 0x10_FFFF

X 3: Declare source in utf8 for identifiers and literals
Without the all-critical "use utf8" declaration, putting UTFX8 in your literals and
identifiers wonXt work right. If you used the standard preamble just given above, this
already happened. If you did, you can do things like this:

use utf8;

my $measure = "Aangstroem";
my @Xsoft = qw( cp852 cp1251 cp1252 );
my @XXXXXXXXX = qw( XXXX XXXXX );
my @X = qw( koi8-f koi8-u koi8-r );
my $motto = "X X X"; # FAMILY, GROWING HEART, DROMEDARY CAMEL

If you forget "use utf8", high bytes will be misunderstood as separate characters, and
nothing will work right.

X 4: Characters and their numbers
The "ord" and "chr" functions work transparently on all codepoints, not just on ASCII
alone X nor in fact, not even just on Unicode alone.

# ASCII characters
ord("A")
chr(65)

# characters from the Basic Multilingual Plane
ord("X")
chr(0x3A3)

# beyond the BMP
ord("X") # MATHEMATICAL ITALIC SMALL N
chr(0x1D45B)

# beyond Unicode! (up to MAXINT)
ord("\x{20_0000}")
chr(0x20_0000)

X 5: Unicode literals by character number
In an interpolated literal, whether a double-quoted string or a regex, you may specify a
character by its number using the "\x{HHHHHH}" escape.

String: "\x{3a3}"
Regex: /\x{3a3}/

String: "\x{1d45b}"
Regex: /\x{1d45b}/

# even non-BMP ranges in regex work fine
/[\x{1D434}-\x{1D467}]/

X 6: Get character name by number
use charnames ();
my $name = charnames::viacode(0x03A3);

X 7: Get character number by name
use charnames ();
my $number = charnames::vianame("GREEK CAPITAL LETTER SIGMA");

X 8: Unicode named characters
Use the "\N{charname}" notation to get the character by that name for use in interpolated
literals (double-quoted strings and regexes). In v5.16, there is an implicit

use charnames qw(:full :short);

But prior to v5.16, you must be explicit about which set of charnames you want. The
":full" names are the official Unicode character name, alias, or sequence, which all share
a namespace.

use charnames qw(:full :short latin greek);

"\N{MATHEMATICAL ITALIC SMALL N}" # :full
"\N{GREEK CAPITAL LETTER SIGMA}" # :full

Anything else is a Perl-specific convenience abbreviation. Specify one or more scripts by
names if you want short names that are script-specific.

"\N{Greek:Sigma}" # :short
"\N{ae}" # latin
"\N{epsilon}" # greek

The v5.16 release also supports a ":loose" import for loose matching of character names,
which works just like loose matching of property names: that is, it disregards case,
whitespace, and underscores:

"\N{euro sign}" # :loose (from v5.16)

X 9: Unicode named sequences
These look just like character names but return multiple codepoints. Notice the %vx
vector-print functionality in "printf".

use charnames qw(:full);
my $seq = "\N{LATIN CAPITAL LETTER A WITH MACRON AND GRAVE}";
printf "U+%v04X\n", $seq;
U+0100.0300

X 10: Custom named characters
Use ":alias" to give your own lexically scoped nicknames to existing characters, or even
to give unnamed private-use characters useful names.

use charnames ":full", ":alias" => {
ecute => "LATIN SMALL LETTER E WITH ACUTE",
"APPLE LOGO" => 0xF8FF, # private use character
};

"\N{ecute}"
"\N{APPLE LOGO}"

X 11: Names of CJK codepoints
Sinograms like XXXX come back with character names of "CJK UNIFIED IDEOGRAPH-6771" and
"CJK UNIFIED IDEOGRAPH-4EAC", because their XnamesX vary. The CPAN "Unicode::Unihan"
module has a large database for decoding these (and a whole lot more), provided you know
how to understand its output.

# cpan -i Unicode::Unihan
use Unicode::Unihan;
my $str = "XX";
my $unhan = Unicode::Unihan->new;
for my $lang (qw(Mandarin Cantonese Korean JapaneseOn JapaneseKun)) {
printf "CJK $str in %-12s is ", $lang;
say $unhan->$lang($str);
}

prints:

CJK XX in Mandarin is DONG1JING1
CJK XX in Cantonese is dung1ging1
CJK XX in Korean is TONGKYENG
CJK XX in JapaneseOn is TOUKYOU KEI KIN
CJK XX in JapaneseKun is HIGASHI AZUMAMIYAKO

If you have a specific romanization scheme in mind, use the specific module:

# cpan -i Lingua::JA::Romanize::Japanese
use Lingua::JA::Romanize::Japanese;
my $k2r = Lingua::JA::Romanize::Japanese->new;
my $str = "XX";
say "Japanese for $str is ", $k2r->chars($str);

prints

Japanese for XX is toukyou

X 12: Explicit encode/decode
On rare occasion, such as a database read, you may be given encoded text you need to
decode.

use Encode qw(encode decode);

my $chars = decode("shiftjis", $bytes, 1);
# OR
my $bytes = encode("MIME-Header-ISO_2022_JP", $chars, 1);

For streams all in the same encoding, don't use encode/decode; instead set the file
encoding when you open the file or immediately after with "binmode" as described later
below.

X 13: Decode program arguments as utf8
$ perl -CA ...
or
$ export PERL_UNICODE=A
or
use Encode qw(decode_utf8);
@ARGV = map { decode_utf8($_, 1) } @ARGV;

X 14: Decode program arguments as locale encoding
# cpan -i Encode::Locale
use Encode qw(locale);
use Encode::Locale;

# use "locale" as an arg to encode/decode
@ARGV = map { decode(locale => $_, 1) } @ARGV;

X 15: Declare STD{IN,OUT,ERR} to be utf8
Use a command-line option, an environment variable, or else call "binmode" explicitly:

$ perl -CS ...
or
$ export PERL_UNICODE=S
or
use open qw(:std :utf8);
or
binmode(STDIN, ":utf8");
binmode(STDOUT, ":utf8");
binmode(STDERR, ":utf8");

X 16: Declare STD{IN,OUT,ERR} to be in locale encoding
# cpan -i Encode::Locale
use Encode;
use Encode::Locale;

# or as a stream for binmode or open
binmode STDIN, ":encoding(console_in)" if -t STDIN;
binmode STDOUT, ":encoding(console_out)" if -t STDOUT;
binmode STDERR, ":encoding(console_out)" if -t STDERR;

X 17: Make file I/O default to utf8
Files opened without an encoding argument will be in UTF-8:

$ perl -CD ...
or
$ export PERL_UNICODE=D
or
use open qw(:utf8);

X 18: Make all I/O and args default to utf8
$ perl -CSDA ...
or
$ export PERL_UNICODE=SDA
or
use open qw(:std :utf8);
use Encode qw(decode_utf8);
@ARGV = map { decode_utf8($_, 1) } @ARGV;

X 19: Open file with specific encoding
Specify stream encoding. This is the normal way to deal with encoded text, not by calling
low-level functions.

# input file
open(my $in_file, "< :encoding(UTF-16)", "wintext");
OR
open(my $in_file, "<", "wintext");
binmode($in_file, ":encoding(UTF-16)");
THEN
my $line = <$in_file>;

# output file
open($out_file, "> :encoding(cp1252)", "wintext");
OR
open(my $out_file, ">", "wintext");
binmode($out_file, ":encoding(cp1252)");
THEN
print $out_file "some text\n";

More layers than just the encoding can be specified here. For example, the incantation
":raw :encoding(UTF-16LE) :crlf" includes implicit CRLF handling.

X 20: Unicode casing
Unicode casing is very different from ASCII casing.

uc("henry X") # "HENRY X"
uc("tschuess") # "TSCHUeSS" notice ss => SS

# both are true:
"tschuess" =~ /TSCHUeSS/i # notice ss => SS
"XXXXXXX" =~ /XXXXXXX/i # notice X,X,X sameness

X 21: Unicode case-insensitive comparisons
Also available in the CPAN Unicode::CaseFold module, the new "fc" XfoldcaseX function from
v5.16 grants access to the same Unicode casefolding as the "/i" pattern modifier has
always used:

use feature "fc"; # fc() function is from v5.16

# sort case-insensitively
my @sorted = sort { fc($a) cmp fc($b) } @list;

# both are true:
fc("tschuess") eq fc("TSCHUeSS")
fc("XXXXXXX") eq fc("XXXXXXX")

X 22: Match Unicode linebreak sequence in regex
A Unicode linebreak matches the two-character CRLF grapheme or any of seven vertical
whitespace characters. Good for dealing with textfiles coming from different operating
systems.

\R

s/\R/\n/g; # normalize all linebreaks to \n

X 23: Get character category
Find the general category of a numeric codepoint.

use Unicode::UCD qw(charinfo);
my $cat = charinfo(0x3A3)->{category}; # "Lu"

X 24: Disabling Unicode-awareness in builtin charclasses
Disable "\w", "\b", "\s", "\d", and the POSIX classes from working correctly on Unicode
either in this scope, or in just one regex.

use v5.14;
use re "/a";

# OR

my($num) = $str =~ /(\d+)/a;

Or use specific un-Unicode properties, like "\p{ahex}" and "\p{POSIX_Digit"}. Properties
still work normally no matter what charset modifiers ("/d /u /l /a /aa") should be effect.

X 25: Match Unicode properties in regex with \p, \P
These all match a single codepoint with the given property. Use "\P" in place of "\p" to
match one codepoint lacking that property.

\pL, \pN, \pS, \pP, \pM, \pZ, \pC
\p{Sk}, \p{Ps}, \p{Lt}
\p{alpha}, \p{upper}, \p{lower}
\p{Latin}, \p{Greek}
\p{script=Latin}, \p{script=Greek}
\p{East_Asian_Width=Wide}, \p{EA=W}
\p{Line_Break=Hyphen}, \p{LB=HY}
\p{Numeric_Value=4}, \p{NV=4}

X 26: Custom character properties
Define at compile-time your own custom character properties for use in regexes.

# using private-use characters
sub In_Tengwar { "E000\tE07F\n" }

if (/\p{In_Tengwar}/) { ... }

# blending existing properties
sub Is_GraecoRoman_Title {<<'END_OF_SET'}
+utf8::IsLatin
+utf8::IsGreek
&utf8::IsTitle
END_OF_SET

if (/\p{Is_GraecoRoman_Title}/ { ... }

X 27: Unicode normalization
Typically render into NFD on input and NFC on output. Using NFKC or NFKD functions
improves recall on searches, assuming you've already done to the same text to be searched.
Note that this is about much more than just pre- combined compatibility glyphs; it also
reorders marks according to their canonical combining classes and weeds out singletons.

use Unicode::Normalize;
my $nfd = NFD($orig);
my $nfc = NFC($orig);
my $nfkd = NFKD($orig);
my $nfkc = NFKC($orig);

X 28: Convert non-ASCII Unicode numerics
Unless youXve used "/a" or "/aa", "\d" matches more than ASCII digits only, but PerlXs
implicit string-to-number conversion does not current recognize these. HereXs how to
convert such strings manually.

use v5.14; # needed for num() function
use Unicode::UCD qw(num);
my $str = "got X and XXXX and X and here";
my @nums = ();
while ($str =~ /(\d+|\N)/g) { # not just ASCII!
push @nums, num($1);
}
say "@nums"; # 12 4567 0.875

use charnames qw(:full);
my $nv = num("\N{RUMI DIGIT ONE}\N{RUMI DIGIT TWO}");

X 29: Match Unicode grapheme cluster in regex
Programmer-visible XcharactersX are codepoints matched by "/./s", but user-visible
XcharactersX are graphemes matched by "/\X/".

# Find vowel *plus* any combining diacritics,underlining,etc.
my $nfd = NFD($orig);
$nfd =~ / (?=[aeiou]) \X /xi

X 30: Extract by grapheme instead of by codepoint (regex)
# match and grab five first graphemes
my($first_five) = $str =~ /^ ( \X{5} ) /x;

X 31: Extract by grapheme instead of by codepoint (substr)
# cpan -i Unicode::GCString
use Unicode::GCString;
my $gcs = Unicode::GCString->new($str);
my $first_five = $gcs->substr(0, 5);

X 32: Reverse string by grapheme
Reversing by codepoint messes up diacritics, mistakenly converting "creme brulee" into
"eelXurb emXerc" instead of into "eelurb emerc"; so reverse by grapheme instead. Both
these approaches work right no matter what normalization the string is in:

$str = join("", reverse $str =~ /\X/g);

# OR: cpan -i Unicode::GCString
use Unicode::GCString;
$str = reverse Unicode::GCString->new($str);

X 33: String length in graphemes
The string "brulee" has six graphemes but up to eight codepoints. This counts by
grapheme, not by codepoint:

my $str = "brulee";
my $count = 0;
while ($str =~ /\X/g) { $count++ }

# OR: cpan -i Unicode::GCString
use Unicode::GCString;
my $gcs = Unicode::GCString->new($str);
my $count = $gcs->length;

X 34: Unicode column-width for printing
PerlXs "printf", "sprintf", and "format" think all codepoints take up 1 print column, but
many take 0 or 2. Here to show that normalization makes no difference, we print out both
forms:

use Unicode::GCString;
use Unicode::Normalize;

my @words = qw/creme brulee/;
@words = map { NFC($_), NFD($_) } @words;

for my $str (@words) {
my $gcs = Unicode::GCString->new($str);
my $cols = $gcs->columns;
my $pad = " " x (10 - $cols);
say str, $pad, " |";
}

generates this to show that it pads correctly no matter the normalization:

creme |
creXme |
brulee |
bruXleXe |

X 35: Unicode collation
Text sorted by numeric codepoint follows no reasonable alphabetic order; use the UCA for
sorting text.

use Unicode::Collate;
my $col = Unicode::Collate->new();
my @list = $col->sort(@old_list);

See the ucsort program from the Unicode::Tussle CPAN module for a convenient command-line
interface to this module.

X 36: Case- and accent-insensitive Unicode sort
Specify a collation strength of level 1 to ignore case and diacritics, only looking at the
basic character.

use Unicode::Collate;
my $col = Unicode::Collate->new(level => 1);
my @list = $col->sort(@old_list);

X 37: Unicode locale collation
Some locales have special sorting rules.

# either use v5.12, OR: cpan -i Unicode::Collate::Locale
use Unicode::Collate::Locale;
my $col = Unicode::Collate::Locale->new(locale => "de__phonebook");
my @list = $col->sort(@old_list);

The ucsort program mentioned above accepts a "--locale" parameter.

X 38: Making "cmp" work on text instead of codepoints
Instead of this:

@srecs = sort {
$b->{AGE} <=> $a->{AGE}
||
$a->{NAME} cmp $b->{NAME}
} @recs;

Use this:

my $coll = Unicode::Collate->new();
for my $rec (@recs) {
$rec->{NAME_key} = $coll->getSortKey( $rec->{NAME} );
}
@srecs = sort {
$b->{AGE} <=> $a->{AGE}
||
$a->{NAME_key} cmp $b->{NAME_key}
} @recs;

X 39: Case- and accent-insensitive comparisons
Use a collator object to compare Unicode text by character instead of by codepoint.

use Unicode::Collate;
my $es = Unicode::Collate->new(
level => 1,
normalization => undef
);

# now both are true:
$es->eq("Garcia", "GARCIA" );
$es->eq("Marquez", "MARQUEZ");

X 40: Case- and accent-insensitive locale comparisons
Same, but in a specific locale.

my $de = Unicode::Collate::Locale->new(
locale => "de__phonebook",
);

# now this is true:
$de->eq("tschuess", "TSCHUESS"); # notice ue => UE, ss => SS

X 41: Unicode linebreaking
Break up text into lines according to Unicode rules.

# cpan -i Unicode::LineBreak
use Unicode::LineBreak;
use charnames qw(:full);

my $para = "This is a super\N{HYPHEN}long string. " x 20;
my $fmt = Unicode::LineBreak->new;
print $fmt->break($para), "\n";

X 42: Unicode text in DBM hashes, the tedious way
Using a regular Perl string as a key or value for a DBM hash will trigger a wide character
exception if any codepoints wonXt fit into a byte. HereXs how to manually manage the
translation:

use DB_File;
use Encode qw(encode decode);
tie %dbhash, "DB_File", "pathname";

# STORE

# assume $uni_key and $uni_value are abstract Unicode strings
my $enc_key = encode("UTF-8", $uni_key, 1);
my $enc_value = encode("UTF-8", $uni_value, 1);
$dbhash{$enc_key} = $enc_value;

# FETCH

# assume $uni_key holds a normal Perl string (abstract Unicode)
my $enc_key = encode("UTF-8", $uni_key, 1);
my $enc_value = $dbhash{$enc_key};
my $uni_value = decode("UTF-8", $enc_value, 1);

X 43: Unicode text in DBM hashes, the easy way
HereXs how to implicitly manage the translation; all encoding and decoding is done
automatically, just as with streams that have a particular encoding attached to them:

use DB_File;
use DBM_Filter;

my $dbobj = tie %dbhash, "DB_File", "pathname";
$dbobj->Filter_Value("utf8"); # this is the magic bit

# STORE

# assume $uni_key and $uni_value are abstract Unicode strings
$dbhash{$uni_key} = $uni_value;

# FETCH

# $uni_key holds a normal Perl string (abstract Unicode)
my $uni_value = $dbhash{$uni_key};

X 44: PROGRAM: Demo of Unicode collation and printing
HereXs a full program showing how to make use of locale-sensitive sorting, Unicode casing,
and managing print widths when some of the characters take up zero or two columns, not
just one column each time. When run, the following program produces this nicely aligned
output:

Creme Brulee....... X2.00
Eclair............. X1.60
Fideua............. X4.20
Hamburger.......... X6.00
Jamon Serrano...... X4.45
Linguica........... X7.00
Pate............... X4.15
Pears.............. X2.00
Peches............. X2.25
Smorbrod........... X5.75
Spaetzle............ X5.50
Xorico............. X3.00
XXXXX.............. X6.50
XXX............. X4.00
XXX............. X2.65
XXXXX......... X8.00
XXXXXXX..... X1.85
XX............... X9.99
XX............... X7.50

Here's that program; tested on v5.14.

#!/usr/bin/env perl
# umenu - demo sorting and printing of Unicode food
#
# (obligatory and increasingly long preamble)
#
use utf8;
use v5.14; # for locale sorting
use strict;
use warnings;
use warnings qw(FATAL utf8); # fatalize encoding faults
use open qw(:std :utf8); # undeclared streams in UTF-8
use charnames qw(:full :short); # unneeded in v5.16

# std modules
use Unicode::Normalize; # std perl distro as of v5.8
use List::Util qw(max); # std perl distro as of v5.10
use Unicode::Collate::Locale; # std perl distro as of v5.14

# cpan modules
use Unicode::GCString; # from CPAN

# forward defs
sub pad($$$);
sub colwidth(_);
sub entitle(_);

my %price = (
"XXXXX" => 6.50, # gyros
"pears" => 2.00, # like um, pears
"linguica" => 7.00, # spicy sausage, Portuguese
"xorico" => 3.00, # chorizo sausage, Catalan
"hamburger" => 6.00, # burgermeister meisterburger
"eclair" => 1.60, # dessert, French
"smorbrod" => 5.75, # sandwiches, Norwegian
"spaetzle" => 5.50, # Bayerisch noodles, little sparrows
"XX" => 7.50, # bao1 zi5, steamed pork buns, Mandarin
"jamon serrano" => 4.45, # country ham, Spanish
"peches" => 2.25, # peaches, French
"XXXXXXX" => 1.85, # cream-filled pastry like eclair
"XXX" => 4.00, # makgeolli, Korean rice wine
"XX" => 9.99, # sushi, Japanese
"XXX" => 2.65, # omochi, rice cakes, Japanese
"creme brulee" => 2.00, # crema catalana
"fideua" => 4.20, # more noodles, Valencian
# (Catalan=fideuada)
"pate" => 4.15, # gooseliver paste, French
"XXXXX" => 8.00, # okonomiyaki, Japanese
);

my $width = 5 + max map { colwidth } keys %price;

# So the Asian stuff comes out in an order that someone
# who reads those scripts won't freak out over; the
# CJK stuff will be in JIS X 0208 order that way.
my $coll = Unicode::Collate::Locale->new(locale => "ja");

for my $item ($coll->sort(keys %price)) {
print pad(entitle($item), $width, ".");
printf " X%.2f\n", $price{$item};
}

sub pad($$$) {
my($str, $width, $padchar) = @_;
return $str . ($padchar x ($width - colwidth($str)));
}

sub colwidth(_) {
my($str) = @_;
return Unicode::GCString->new($str)->columns;
}

sub entitle(_) {
my($str) = @_;
$str =~ s{ (?=\pL)(\S) (\S*) }
{ ucfirst($1) . lc($2) }xge;
return $str;
}

Use perlunicook online using onworks.net services