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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
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            <h1>perllocale</h1>


  <!--    -->
<ul><li><a href="#NAME">NAME</a><li><a href="#DESCRIPTION">DESCRIPTION</a><li><a href="#WHAT-IS-A-LOCALE">WHAT IS A LOCALE</a><li><a href="#PREPARING-TO-USE-LOCALES">PREPARING TO USE LOCALES</a><li><a href="#USING-LOCALES">USING LOCALES</a><ul><li><a href="#The-%22use-locale%22-pragma">The "use locale" pragma</a><li><a href="#The-setlocale-function">The setlocale function</a><li><a href="#Finding-locales">Finding locales</a><li><a href="#LOCALE-PROBLEMS">LOCALE PROBLEMS</a><li><a href="#Testing-for-broken-locales">Testing for broken locales</a><li><a href="#Temporarily-fixing-locale-problems">Temporarily fixing locale problems</a><li><a href="#Permanently-fixing-locale-problems">Permanently fixing locale problems</a><li><a href="#Permanently-fixing-your-system's-locale-configuration">Permanently fixing your system's locale configuration</a><li><a href="#Fixing-system-locale-configuration">Fixing system locale configuration</a><li><a href="#The-localeconv-function">The localeconv function</a><li><a href="#I18N%3a%3aLanginfo">I18N::Langinfo</a></ul><li><a href="#LOCALE-CATEGORIES">LOCALE CATEGORIES</a><ul><li><a href="#Category-LC_COLLATE%3a-Collation%3a-Text-Comparisons-and-Sorting">Category LC_COLLATE: Collation: Text Comparisons and Sorting</a><li><a href="#Category-LC_CTYPE%3a-Character-Types">Category LC_CTYPE: Character Types</a><li><a href="#Category-LC_NUMERIC%3a-Numeric-Formatting">Category LC_NUMERIC: Numeric Formatting</a><li><a href="#Category-LC_MONETARY%3a-Formatting-of-monetary-amounts">Category LC_MONETARY: Formatting of monetary amounts</a><li><a href="#Category-LC_TIME%3a-Respresentation-of-time">Category LC_TIME: Respresentation of time</a><li><a href="#Other-categories">Other categories</a></ul><li><a href="#SECURITY">SECURITY</a><li><a href="#ENVIRONMENT">ENVIRONMENT</a><ul><li><a href="#Examples">Examples</a></ul><li><a href="#NOTES">NOTES</a><ul><li><a href="#String-eval-and-LC_NUMERIC">String eval and LC_NUMERIC</a><li><a href="#Backward-compatibility">Backward compatibility</a><li><a href="#I18N%3aCollate-obsolete">I18N:Collate obsolete</a><li><a href="#Sort-speed-and-memory-use-impacts">Sort speed and memory use impacts</a><li><a href="#Freely-available-locale-definitions">Freely available locale definitions</a><li><a href="#I18n-and-l10n">I18n and l10n</a><li><a href="#An-imperfect-standard">An imperfect standard</a></ul><li><a href="#Unicode-and-UTF-8">Unicode and UTF-8</a><li><a href="#BUGS">BUGS</a><ul><li><a href="#Collation-of-strings-containing-embedded-NUL-characters">Collation of strings containing embedded NUL characters</a><li><a href="#Broken-systems">Broken systems</a></ul><li><a href="#SEE-ALSO">SEE ALSO</a><li><a href="#HISTORY">HISTORY</a></ul><a name="NAME"></a><h1>NAME</h1>
<p>perllocale - Perl locale handling (internationalization and localization)</p>
<a name="DESCRIPTION"></a><h1>DESCRIPTION</h1>
<p>In the beginning there was ASCII, the "American Standard Code for
Information Interchange", which works quite well for Americans with
their English alphabet and dollar-denominated currency.  But it doesn't
work so well even for other English speakers, who may use different
currencies, such as the pound sterling (as the symbol for that currency
is not in ASCII); and it's hopelessly inadequate for many of the
thousands of the world's other languages.</p>
<p>To address these deficiencies, the concept of locales was invented
(formally the ISO C, XPG4, POSIX 1.c "locale system").  And applications
were and are being written that use the locale mechanism.  The process of
making such an application take account of its users' preferences in
these kinds of matters is called <b>internationalization</b> (often
abbreviated as <b>i18n</b>); telling such an application about a particular
set of preferences is known as <b>localization</b> (<b>l10n</b>).</p>
<p>Perl has been extended to support the locale system.  This
is controlled per application by using one pragma, one function call,
and several environment variables.</p>
<p>Unfortunately, there are quite a few deficiencies with the design (and
often, the implementations) of locales.  Unicode was invented (see
<a href="perlunitut.html">perlunitut</a> for an introduction to that) in part to address these
design deficiencies, and nowadays, there is a series of "UTF-8
locales", based on Unicode.  These are locales whose character set is
Unicode, encoded in UTF-8.  Starting in v5.20, Perl fully supports
UTF-8 locales, except for sorting and string comparisons like <code class="inline">lt</code>
 and
<code class="inline">ge</code>
.  Starting in v5.26, Perl can handle these reasonably as well,
depending on the platform's implementation.  However, for earlier
releases or for better control, use <a href="Unicode/Collate.html">Unicode::Collate</a> .  Perl continues to
support the old non UTF-8 locales as well.  There are currently no UTF-8
locales for EBCDIC platforms.</p>
<p>(Unicode is also creating <code class="inline"><span class="w">CLDR</span></code>
, the "Common Locale Data Repository",
<a href="http://cldr.unicode.org/">http://cldr.unicode.org/</a> which includes more types of information than
are available in the POSIX locale system.  At the time of this writing,
there was no CPAN module that provides access to this XML-encoded data.
However, it is possible to compute the POSIX locale data from them, and
earlier CLDR versions had these already extracted for you as UTF-8 locales
<a href="http://unicode.org/Public/cldr/2.0.1/">http://unicode.org/Public/cldr/2.0.1/</a>.)</p>
<a name="WHAT-IS-A-LOCALE"></a><h1>WHAT IS A LOCALE</h1>
<p>A locale is a set of data that describes various aspects of how various
communities in the world categorize their world.  These categories are
broken down into the following types (some of which include a brief
note here):</p>
<ul>
<li><a name="Category-LC_NUMERIC%3a-Numeric-formatting"></a><b>Category <code class="inline"><span class="w">LC_NUMERIC</span></code>
: Numeric formatting</b>
<p>This indicates how numbers should be formatted for human readability,
for example the character used as the decimal point.</p>
</li>
<li><a name="Category-LC_MONETARY%3a-Formatting-of-monetary-amounts"></a><b>Category <code class="inline"><span class="w">LC_MONETARY</span></code>
: Formatting of monetary amounts</b>
<p>&#xa0;</p>
</li>
<li><a name="Category-LC_TIME%3a-Date%2fTime-formatting"></a><b>Category <code class="inline"><span class="w">LC_TIME</span></code>
: Date/Time formatting</b>
<p>&#xa0;</p>
</li>
<li><a name="Category-LC_MESSAGES%3a-Error-and-other-messages"></a><b>Category <code class="inline"><span class="w">LC_MESSAGES</span></code>
: Error and other messages</b>
<p>This is used by Perl itself only for accessing operating system error
messages via <a href="perlvar.html#%24ERRNO">$!</a> and <a href="perlvar.html#%24EXTENDED_OS_ERROR">$^E</a>.</p>
</li>
<li><a name="Category-LC_COLLATE%3a-Collation"></a><b>Category <code class="inline"><span class="w">LC_COLLATE</span></code>
: Collation</b>
<p>This indicates the ordering of letters for comparison and sorting.
In Latin alphabets, for example, "b", generally follows "a".</p>
</li>
<li><a name="Category-LC_CTYPE%3a-Character-Types"></a><b>Category <code class="inline"><span class="w">LC_CTYPE</span></code>
: Character Types</b>
<p>This indicates, for example if a character is an uppercase letter.</p>
</li>
<li><a name="Other-categories"></a><b>Other categories</b>
<p>Some platforms have other categories, dealing with such things as
measurement units and paper sizes.  None of these are used directly by
Perl, but outside operations that Perl interacts with may use
these.  See <a href="#Not-within-the-scope-of-%22use-locale%22">Not within the scope of use locale</a> below.</p>
</li>
</ul>
<p>More details on the categories used by Perl are given below in <a href="#LOCALE-CATEGORIES">LOCALE CATEGORIES</a>.</p>
<p>Together, these categories go a long way towards being able to customize
a single program to run in many different locations.  But there are
deficiencies, so keep reading.</p>
<a name="PREPARING-TO-USE-LOCALES"></a><h1>PREPARING TO USE LOCALES</h1>
<p>Perl itself (outside the <a href="POSIX.html">POSIX</a> module) will not use locales unless
specifically requested to (but
again note that Perl may interact with code that does use them).  Even
if there is such a request, <b>all</b> of the following must be true
for it to work properly:</p>
<ul>
<li>
<p><b>Your operating system must support the locale system</b>.  If it does,
you should find that the <code class="inline"><span class="i">setlocale</span><span class="s">(</span><span class="s">)</span></code>
 function is a documented part of
its C library.</p>
</li>
<li>
<p><b>Definitions for locales that you use must be installed</b>.  You, or
your system administrator, must make sure that this is the case. The
available locales, the location in which they are kept, and the manner
in which they are installed all vary from system to system.  Some systems
provide only a few, hard-wired locales and do not allow more to be
added.  Others allow you to add "canned" locales provided by the system
supplier.  Still others allow you or the system administrator to define
and add arbitrary locales.  (You may have to ask your supplier to
provide canned locales that are not delivered with your operating
system.)  Read your system documentation for further illumination.</p>
</li>
<li>
<p><b>Perl must believe that the locale system is supported</b>.  If it does,
<code class="inline">perl -V:d_setlocale</code> will say that the value for <code class="inline"><span class="w">d_setlocale</span></code>
 is
<code class="inline"><span class="w">define</span></code>
.</p>
</li>
</ul>
<p>If you want a Perl application to process and present your data
according to a particular locale, the application code should include
the <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 pragma (see <a href="#The-%22use-locale%22-pragma">The use locale pragma</a>) where
appropriate, and <b>at least one</b> of the following must be true:</p>
<dl>
<dt>1</dt><dd>
<p><b>The locale-determining environment variables (see <a href="#ENVIRONMENT">ENVIRONMENT</a>)
must be correctly set up</b> at the time the application is started, either
by yourself or by whomever set up your system account; or</p>
</dd>
<dt>2</dt><dd>
<p><b>The application must set its own locale</b> using the method described in
<a href="#The-setlocale-function">The setlocale function</a>.</p>
</dd>
</dl>
<a name="USING-LOCALES"></a><h1>USING LOCALES</h1>
<a name="The-%22use-locale%22-pragma"></a><h2>The <code class="inline"><span class="q">&quot;use locale&quot;</span></code>
 pragma</h2>
<p>WARNING!  Do NOT use this pragma in scripts that have multiple
<a href="threads.html">threads</a> active.  The locale is not local to a single thread.
Another thread may change the locale at any time, which could cause at a
minimum that a given thread is operating in a locale it isn't expecting
to be in.  On some platforms, segfaults can also occur.  The locale
change need not be explicit; some operations cause perl to change the
locale itself.  You are vulnerable simply by having done a <code class="inline"><span class="q">&quot;use</span>
<span class="q">locale&quot;</span></code>
.</p>
<p>By default, Perl itself (outside the <a href="POSIX.html">POSIX</a> module)
ignores the current locale.  The <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>

pragma tells Perl to use the current locale for some operations.
Starting in v5.16, there are optional parameters to this pragma,
described below, which restrict which operations are affected by it.</p>
<p>The current locale is set at execution time by
<a href="#The-setlocale-function">setlocale()</a> described below.  If that function
hasn't yet been called in the course of the program's execution, the
current locale is that which was determined by the <a href="#ENVIRONMENT">ENVIRONMENT</a> in
effect at the start of the program.
If there is no valid environment, the current locale is whatever the
system default has been set to.   On POSIX systems, it is likely, but
not necessarily, the "C" locale.  On Windows, the default is set via the
computer's <code class="inline"><span class="w">Control</span> <span class="w">Panel</span><span class="w">-&gt;Regional</span> <a class="l_k" href="functions/and.html">and</a> <span class="w">Language</span> <span class="w">Options</span></code>
 (or its
current equivalent).</p>
<p>The operations that are affected by locale are:</p>
<ul>
<li><a name="*Not-within-the-scope-of-%22use-locale%22*"></a><b><b>Not within the scope of <code class="inline"><span class="q">&quot;use locale&quot;</span></code>
</b></b>
<p>Only certain operations originating outside Perl should be affected, as
follows:</p>
<ul>
<li>
<p>The current locale is used when going outside of Perl with
operations like <a href="functions/system.html">system LIST</a> or
<a href="perlop.html#qx%2fSTRING%2f">qx//</a>, if those operations are
locale-sensitive.</p>
</li>
<li>
<p>Also Perl gives access to various C library functions through the
<a href="POSIX.html">POSIX</a> module.  Some of those functions are always affected by the
current locale.  For example, <code class="inline"><span class="i">POSIX::strftime</span><span class="s">(</span><span class="s">)</span></code>
 uses <code class="inline"><span class="w">LC_TIME</span></code>
;
<code class="inline"><span class="i">POSIX::strtod</span><span class="s">(</span><span class="s">)</span></code>
 uses <code class="inline"><span class="w">LC_NUMERIC</span></code>
; <code class="inline"><span class="i">POSIX::strcoll</span><span class="s">(</span><span class="s">)</span></code>
 and
<code class="inline"><span class="i">POSIX::strxfrm</span><span class="s">(</span><span class="s">)</span></code>
 use <code class="inline"><span class="w">LC_COLLATE</span></code>
.  All such functions
will behave according to the current underlying locale, even if that
locale isn't exposed to Perl space.</p>
</li>
<li>
<p>XS modules for all categories but <code class="inline"><span class="w">LC_NUMERIC</span></code>
 get the underlying
locale, and hence any C library functions they call will use that
underlying locale.  For more discussion, see <a href="perlxs.html#CAVEATS">CAVEATS in perlxs</a>.</p>
</li>
</ul>
<p>Note that all C programs (including the perl interpreter, which is
written in C) always have an underlying locale.  That locale is the "C"
locale unless changed by a call to <a href="#The-setlocale-function">setlocale()</a>.  When Perl starts up, it changes the underlying locale to the
one which is indicated by the <a href="#ENVIRONMENT">ENVIRONMENT</a>.  When using the <a href="POSIX.html">POSIX</a>
module or writing XS code, it is important to keep in mind that the
underlying locale may be something other than "C", even if the program
hasn't explicitly changed it.</p>
<p>&#xa0;</p>
</li>
<li><a name="*Lingering-effects-of-use-locale*"></a><b><b>Lingering effects of <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
</b></b>
<p>Certain Perl operations that are set-up within the scope of a
<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 retain that effect even outside the scope.
These include:</p>
<ul>
<li>
<p>The output format of a <a href="functions/write.html">write</a> is determined by an
earlier format declaration (<a href="functions/format.html">format</a>), so whether or not the
output is affected by locale is determined by if the <code class="inline"><a class="l_k" href="functions/format.html">format()</a></code> is
within the scope of a <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
, not whether the <code class="inline"><a class="l_k" href="functions/write.html">write()</a></code>
is.</p>
</li>
<li>
<p>Regular expression patterns can be compiled using
<a href="perlop.html#qr%2fSTRING%2fmsixpodualn">qr//</a> with actual
matching deferred to later.  Again, it is whether or not the compilation
was done within the scope of <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 that determines the match
behavior, not if the matches are done within such a scope or not.</p>
</li>
</ul>
<p>&#xa0;</p>
</li>
<li><a name="*Under-%22use-locale%22%3b*"></a><b><b>Under <code class="inline"><span class="q">&quot;use locale&quot;</span><span class="sc">;</span></code>
</b></b>
<ul>
<li>
<p>All the above operations</p>
</li>
<li>
<p><b>Format declarations</b> (<a href="functions/format.html">format</a>) and hence any subsequent
<code class="inline"><a class="l_k" href="functions/write.html">write()</a></code>s use <code class="inline"><span class="w">LC_NUMERIC</span></code>
.</p>
</li>
<li>
<p><b>stringification and output</b> use <code class="inline"><span class="w">LC_NUMERIC</span></code>
.
These include the results of
<code class="inline"><a class="l_k" href="functions/print.html">print()</a></code>,
<code class="inline"><a class="l_k" href="functions/printf.html">printf()</a></code>,
<code class="inline"><a class="l_k" href="functions/say.html">say()</a></code>,
and
<code class="inline"><a class="l_k" href="functions/sprintf.html">sprintf()</a></code>.</p>
</li>
<li>
<p><b>The comparison operators</b> (<code class="inline">lt</code>
, <code class="inline">le</code>
, <code class="inline">cmp</code>
, <code class="inline">ge</code>
, and <code class="inline">gt</code>
) use
<code class="inline"><span class="w">LC_COLLATE</span></code>
.  <code class="inline"><a class="l_k" href="functions/sort.html">sort()</a></code> is also affected if used without an
explicit comparison function, because it uses <code class="inline">cmp</code>
 by default.</p>
<p><b>Note:</b> <code class="inline">eq</code>
 and <code class="inline">ne</code>
 are unaffected by locale: they always
perform a char-by-char comparison of their scalar operands.  What's
more, if <code class="inline">cmp</code>
 finds that its operands are equal according to the
collation sequence specified by the current locale, it goes on to
perform a char-by-char comparison, and only returns <i>0</i> (equal) if the
operands are char-for-char identical.  If you really want to know whether
two strings--which <code class="inline">eq</code>
 and <code class="inline">cmp</code>
 may consider different--are equal
as far as collation in the locale is concerned, see the discussion in
<a href="#Category-LC_COLLATE-%3a-Collation">Category LC_COLLATE : Collation</a>.</p>
</li>
<li>
<p><b>Regular expressions and case-modification functions</b> (<code class="inline"><a class="l_k" href="functions/uc.html">uc()</a></code>, <code class="inline"><a class="l_k" href="functions/lc.html">lc()</a></code>,
<code class="inline"><a class="l_k" href="functions/ucfirst.html">ucfirst()</a></code>, and <code class="inline"><a class="l_k" href="functions/lcfirst.html">lcfirst()</a></code>) use <code class="inline"><span class="w">LC_CTYPE</span></code>
</p>
</li>
<li>
<p><b>The variables <a href="perlvar.html#%24ERRNO">$!</a></b> (and its synonyms <code class="inline"><span class="i">$ERRNO</span></code>
 and
<code class="inline"><span class="i">$OS_ERROR</span></code>
) <b>and <a href="perlvar.html#%24EXTENDED_OS_ERROR">$^E</a></b> (and its synonym
<code class="inline"><span class="i">$EXTENDED_OS_ERROR</span></code>
) when used as strings use <code class="inline"><span class="w">LC_MESSAGES</span></code>
.</p>
</li>
</ul>
</li>
</ul>
<p>The default behavior is restored with the <code class="inline"><a class="l_k" href="functions/no.html">no</a> <span class="w">locale</span></code>
 pragma, or
upon reaching the end of the block enclosing <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
.
Note that <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 calls may be
nested, and that what is in effect within an inner scope will revert to
the outer scope's rules at the end of the inner scope.</p>
<p>The string result of any operation that uses locale
information is tainted, as it is possible for a locale to be
untrustworthy.  See <a href="#SECURITY">SECURITY</a>.</p>
<p>Starting in Perl v5.16 in a very limited way, and more generally in
v5.22, you can restrict which category or categories are enabled by this
particular instance of the pragma by adding parameters to it.  For
example,</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span> <span class="q">qw(:ctype :numeric)</span><span class="sc">;</span></li></ol></pre><p>enables locale awareness within its scope of only those operations
(listed above) that are affected by <code class="inline"><span class="w">LC_CTYPE</span></code>
 and <code class="inline"><span class="w">LC_NUMERIC</span></code>
.</p>
<p>The possible categories are: <code class="inline"><span class="j">:</span><span class="w">collate</span></code>
, <code class="inline"><span class="j">:</span><span class="w">ctype</span></code>
, <code class="inline"><span class="j">:</span><span class="w">messages</span></code>
,
<code class="inline"><span class="j">:</span><span class="w">monetary</span></code>
, <code class="inline"><span class="j">:</span><span class="w">numeric</span></code>
, <code class="inline"><span class="j">:</span><a class="l_k" href="functions/time.html">time</a></code>
, and the pseudo category
<code class="inline"><span class="j">:</span><span class="w">characters</span></code>
 (described below).</p>
<p>Thus you can say</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span> <span class="q">&#39;:messages&#39;</span><span class="sc">;</span></li></ol></pre><p>and only <a href="perlvar.html#%24ERRNO">$!</a> and <a href="perlvar.html#%24EXTENDED_OS_ERROR">$^E</a>
will be locale aware.  Everything else is unaffected.</p>
<p>Since Perl doesn't currently do anything with the <code class="inline"><span class="w">LC_MONETARY</span></code>

category, specifying <code class="inline"><span class="j">:</span><span class="w">monetary</span></code>
 does effectively nothing.  Some
systems have other categories, such as <code class="inline"><span class="w">LC_PAPER_SIZE</span></code>
, but Perl
also doesn't know anything about them, and there is no way to specify
them in this pragma's arguments.</p>
<p>You can also easily say to use all categories but one, by either, for
example,</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span> <span class="q">&#39;:!ctype&#39;</span><span class="sc">;</span></li><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span> <span class="q">&#39;:not_ctype&#39;</span><span class="sc">;</span></li></ol></pre><p>both of which mean to enable locale awarness of all categories but
<code class="inline"><span class="w">LC_CTYPE</span></code>
.  Only one category argument may be specified in a
<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 if it is of the negated form.</p>
<p>Prior to v5.22 only one form of the pragma with arguments is available:</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span> <span class="q">&#39;:not_characters&#39;</span><span class="sc">;</span></li></ol></pre><p>(and you have to say <code class="inline"><span class="w">not_</span></code>
; you can't use the bang <code class="inline">!</code>
 form).  This
pseudo category is a shorthand for specifying both <code class="inline"><span class="j">:</span><span class="w">collate</span></code>
 and
<code class="inline"><span class="j">:</span><span class="w">ctype</span></code>
.  Hence, in the negated form, it is nearly the same thing as
saying</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span> <span class="q">qw(:messages :monetary :numeric :time)</span><span class="sc">;</span></li></ol></pre><p>We use the term "nearly", because <code class="inline"><span class="j">:</span><span class="w">not_characters</span></code>
 also turns on
<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&#39;unicode_strings&#39;</span></code>
 within its scope.  This form is
less useful in v5.20 and later, and is described fully in
<a href="#Unicode-and-UTF-8">Unicode and UTF-8</a>, but briefly, it tells Perl to not use the
character portions of the locale definition, that is the <code class="inline"><span class="w">LC_CTYPE</span></code>
 and
<code class="inline"><span class="w">LC_COLLATE</span></code>
 categories.  Instead it will use the native character set
(extended by Unicode).  When using this parameter, you are responsible
for getting the external character set translated into the
native/Unicode one (which it already will be if it is one of the
increasingly popular UTF-8 locales).  There are convenient ways of doing
this, as described in <a href="#Unicode-and-UTF-8">Unicode and UTF-8</a>.</p>
<a name="The-setlocale-function"></a><h2>The setlocale function</h2>
<p>WARNING!  Do NOT use this function in a <a href="threads.html">thread</a>.  The locale
will change in all other threads at the same time, and should your
thread get paused by the operating system, and another started, that
thread will not have the locale it is expecting.  On some platforms,
there can be a race leading to segfaults if two threads call this
function nearly simultaneously.</p>
<p>You can switch locales as often as you wish at run time with the
<code class="inline"><span class="i">POSIX::setlocale</span><span class="s">(</span><span class="s">)</span></code>
 function:</p>
<pre class="verbatim"><ol><li>        <span class="c"># Import locale-handling tool set from POSIX module.</span></li><li>        <span class="c"># This example uses: setlocale -- the function call</span></li><li>        <span class="c">#                    LC_CTYPE -- explained below</span></li><li>        <span class="c"># (Showing the testing for success/failure of operations is</span></li><li>        <span class="c"># omitted in these examples to avoid distracting from the main</span></li><li>        <span class="c"># point)</span></li><li></li><li>        <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(locale_h)</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/my.html">my</a> <span class="i">$old_locale</span><span class="sc">;</span></li><li></li><li>        <span class="c"># query and save the old locale</span></li><li>        <span class="i">$old_locale</span> = <span class="i">setlocale</span><span class="s">(</span><span class="w">LC_CTYPE</span><span class="s">)</span><span class="sc">;</span></li><li></li><li>        <span class="i">setlocale</span><span class="s">(</span><span class="w">LC_CTYPE</span><span class="cm">,</span> <span class="q">&quot;fr_CA.ISO8859-1&quot;</span><span class="s">)</span><span class="sc">;</span></li><li>        <span class="c"># LC_CTYPE now in locale &quot;French, Canada, codeset ISO 8859-1&quot;</span></li><li></li><li>        <span class="i">setlocale</span><span class="s">(</span><span class="w">LC_CTYPE</span><span class="cm">,</span> <span class="q">&quot;&quot;</span><span class="s">)</span><span class="sc">;</span></li><li>        <span class="c"># LC_CTYPE now reset to the default defined by the</span></li><li>        <span class="c"># LC_ALL/LC_CTYPE/LANG environment variables, or to the system</span></li><li>        <span class="c"># default.  See below for documentation.</span></li><li></li><li>        <span class="c"># restore the old locale</span></li><li>        <span class="i">setlocale</span><span class="s">(</span><span class="w">LC_CTYPE</span><span class="cm">,</span> <span class="i">$old_locale</span><span class="s">)</span><span class="sc">;</span></li></ol></pre><p>The first argument of <code class="inline"><span class="i">setlocale</span><span class="s">(</span><span class="s">)</span></code>
 gives the <b>category</b>, the second the
<b>locale</b>.  The category tells in what aspect of data processing you
want to apply locale-specific rules.  Category names are discussed in
<a href="#LOCALE-CATEGORIES">LOCALE CATEGORIES</a> and <a href="#ENVIRONMENT">ENVIRONMENT</a>.  The locale is the name of a
collection of customization information corresponding to a particular
combination of language, country or territory, and codeset.  Read on for
hints on the naming of locales: not all systems name locales as in the
example.</p>
<p>If no second argument is provided and the category is something other
than <code class="inline"><span class="w">LC_ALL</span></code>
, the function returns a string naming the current locale
for the category.  You can use this value as the second argument in a
subsequent call to <code class="inline"><span class="i">setlocale</span><span class="s">(</span><span class="s">)</span></code>
, <b>but</b> on some platforms the string
is opaque, not something that most people would be able to decipher as
to what locale it means.</p>
<p>If no second argument is provided and the category is <code class="inline"><span class="w">LC_ALL</span></code>
, the
result is implementation-dependent.  It may be a string of
concatenated locale names (separator also implementation-dependent)
or a single locale name.  Please consult your <i>setlocale(3)</i> man page for
details.</p>
<p>If a second argument is given and it corresponds to a valid locale,
the locale for the category is set to that value, and the function
returns the now-current locale value.  You can then use this in yet
another call to <code class="inline"><span class="i">setlocale</span><span class="s">(</span><span class="s">)</span></code>
.  (In some implementations, the return
value may sometimes differ from the value you gave as the second
argument--think of it as an alias for the value you gave.)</p>
<p>As the example shows, if the second argument is an empty string, the
category's locale is returned to the default specified by the
corresponding environment variables.  Generally, this results in a
return to the default that was in force when Perl started up: changes
to the environment made by the application after startup may or may not
be noticed, depending on your system's C library.</p>
<p>Note that when a form of <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 that doesn't include all
categories is specified, Perl ignores the excluded categories.</p>
<p>If <code class="inline"><span class="i">set_locale</span><span class="s">(</span><span class="s">)</span></code>
 fails for some reason (for example, an attempt to set
to a locale unknown to the system), the locale for the category is not
changed, and the function returns <code class="inline"><a class="l_k" href="functions/undef.html">undef</a></code>.</p>
<p>For further information about the categories, consult <i>setlocale(3)</i>.</p>
<a name="Finding-locales"></a><h2>Finding locales</h2>
<p>For locales available in your system, consult also <i>setlocale(3)</i> to
see whether it leads to the list of available locales (search for the
<i>SEE ALSO</i> section).  If that fails, try the following command lines:</p>
<pre class="verbatim"><ol><li>        <span class="w">locale</span> -<span class="w">a</span></li><li></li><li>        <span class="w">nlsinfo</span></li><li></li><li>        <span class="w">ls</span> /<span class="w">usr</span>/<span class="w">lib</span>/<span class="w">nls</span>/<span class="w">loc</span></li><li></li><li>        <span class="w">ls</span> /<span class="w">usr</span>/<span class="w">lib</span>/<span class="w">locale</span></li><li></li><li>        <span class="w">ls</span> /<span class="w">usr</span>/<span class="w">lib</span>/<span class="w">nls</span></li><li></li><li>	<span class="w">ls</span> /<span class="w">usr</span>/<span class="w">share</span>/<span class="w">locale</span></li></ol></pre><p>and see whether they list something resembling these</p>
<pre class="verbatim"><ol><li>        en_US.ISO8859-1     de_DE.ISO8859-1     ru_RU.ISO8859-5</li><li>        en_US.iso88591      de_DE.iso88591      ru_RU.iso88595</li><li>        en_US               de_DE               ru_RU</li><li>        en                  de                  ru</li><li>        english             german              russian</li><li>        english.iso88591    german.iso88591     russian.iso88595</li><li>        english.roman8                          russian.koi8r</li></ol></pre><p>Sadly, even though the calling interface for <code class="inline"><span class="i">setlocale</span><span class="s">(</span><span class="s">)</span></code>
 has been
standardized, names of locales and the directories where the
configuration resides have not been.  The basic form of the name is
<i>language_territory</i><b>.</b><i>codeset</i>, but the latter parts after
<i>language</i> are not always present.  The <i>language</i> and <i>country</i>
are usually from the standards <b>ISO 3166</b> and <b>ISO 639</b>, the
two-letter abbreviations for the countries and the languages of the
world, respectively.  The <i>codeset</i> part often mentions some <b>ISO
8859</b> character set, the Latin codesets.  For example, <code class="inline"><span class="w">ISO</span> <span class="n">8859</span>-<span class="n">1</span></code>

is the so-called "Western European codeset" that can be used to encode
most Western European languages adequately.  Again, there are several
ways to write even the name of that one standard.  Lamentably.</p>
<p>Two special locales are worth particular mention: "C" and "POSIX".
Currently these are effectively the same locale: the difference is
mainly that the first one is defined by the C standard, the second by
the POSIX standard.  They define the <b>default locale</b> in which
every program starts in the absence of locale information in its
environment.  (The <i>default</i> default locale, if you will.)  Its language
is (American) English and its character codeset ASCII or, rarely, a
superset thereof (such as the "DEC Multinational Character Set
(DEC-MCS)").  <b>Warning</b>. The C locale delivered by some vendors
may not actually exactly match what the C standard calls for.  So
beware.</p>
<p><b>NOTE</b>: Not all systems have the "POSIX" locale (not all systems are
POSIX-conformant), so use "C" when you need explicitly to specify this
default locale.</p>
<a name="LOCALE-PROBLEMS"></a><h2>LOCALE PROBLEMS</h2>
<p>You may encounter the following warning message at Perl startup:</p>
<pre class="verbatim"><ol><li>	perl: warning: Setting locale failed.</li><li>	perl: warning: Please check that your locale settings:</li><li>	        LC_ALL = "En_US",</li><li>	        LANG = (unset)</li><li>	    are supported and installed on your system.</li><li>	perl: warning: Falling back to the standard locale ("C").</li></ol></pre><p>This means that your locale settings had <code class="inline"><span class="w">LC_ALL</span></code>
 set to "En_US" and
LANG exists but has no value.  Perl tried to believe you but could not.
Instead, Perl gave up and fell back to the "C" locale, the default locale
that is supposed to work no matter what.  (On Windows, it first tries
falling back to the system default locale.)  This usually means your
locale settings were wrong, they mention locales your system has never
heard of, or the locale installation in your system has problems (for
example, some system files are broken or missing).  There are quick and
temporary fixes to these problems, as well as more thorough and lasting
fixes.</p>
<a name="Testing-for-broken-locales"></a><h2>Testing for broken locales</h2>
<p>If you are building Perl from source, the Perl test suite file
<i>lib/locale.t</i> can be used to test the locales on your system.
Setting the environment variable <code class="inline"><span class="w">PERL_DEBUG_FULL_TEST</span></code>
 to 1
will cause it to output detailed results.  For example, on Linux, you
could say</p>
<pre class="verbatim"><ol><li> <span class="w">PERL_DEBUG_FULL_TEST</span>=<span class="n">1</span> .<span class="q">/perl -T -Ilib lib/</span><span class="w">locale</span>.<span class="w">t</span> &gt; <span class="w">locale</span>.<a class="l_k" href="functions/log.html">log</a> <span class="n">2</span>&gt;<span class="i">&amp;1</span></li></ol></pre><p>Besides many other tests, it will test every locale it finds on your
system to see if they conform to the POSIX standard.  If any have
errors, it will include a summary near the end of the output of which
locales passed all its tests, and which failed, and why.</p>
<a name="Temporarily-fixing-locale-problems"></a><h2>Temporarily fixing locale problems</h2>
<p>The two quickest fixes are either to render Perl silent about any
locale inconsistencies or to run Perl under the default locale "C".</p>
<p>Perl's moaning about locale problems can be silenced by setting the
environment variable <code class="inline"><span class="w">PERL_BADLANG</span></code>
 to "0" or "".
This method really just sweeps the problem under the carpet: you tell
Perl to shut up even when Perl sees that something is wrong.  Do not
be surprised if later something locale-dependent misbehaves.</p>
<p>Perl can be run under the "C" locale by setting the environment
variable <code class="inline"><span class="w">LC_ALL</span></code>
 to "C".  This method is perhaps a bit more civilized
than the <code class="inline"><span class="w">PERL_BADLANG</span></code>
 approach, but setting <code class="inline"><span class="w">LC_ALL</span></code>
 (or
other locale variables) may affect other programs as well, not just
Perl.  In particular, external programs run from within Perl will see
these changes.  If you make the new settings permanent (read on), all
programs you run see the changes.  See <a href="#ENVIRONMENT">ENVIRONMENT</a> for
the full list of relevant environment variables and <a href="#USING-LOCALES">USING LOCALES</a>
for their effects in Perl.  Effects in other programs are
easily deducible.  For example, the variable <code class="inline"><span class="w">LC_COLLATE</span></code>
 may well affect
your <b>sort</b> program (or whatever the program that arranges "records"
alphabetically in your system is called).</p>
<p>You can test out changing these variables temporarily, and if the
new settings seem to help, put those settings into your shell startup
files.  Consult your local documentation for the exact details.  For
Bourne-like shells (<b>sh</b>, <b>ksh</b>, <b>bash</b>, <b>zsh</b>):</p>
<pre class="verbatim"><ol><li>	LC_ALL=en_US.ISO8859-1</li><li>	export LC_ALL</li></ol></pre><p>This assumes that we saw the locale "en_US.ISO8859-1" using the commands
discussed above.  We decided to try that instead of the above faulty
locale "En_US"--and in Cshish shells (<b>csh</b>, <b>tcsh</b>)</p>
<pre class="verbatim"><ol><li>	<span class="w">setenv</span> <span class="w">LC_ALL</span> <span class="w">en_US</span>.<span class="w">ISO8859</span>-<span class="n">1</span></li></ol></pre><p>or if you have the "env" application you can do (in any shell)</p>
<pre class="verbatim"><ol><li>	env LC_ALL=en_US.ISO8859-1 perl ...</li></ol></pre><p>If you do not know what shell you have, consult your local
helpdesk or the equivalent.</p>
<a name="Permanently-fixing-locale-problems"></a><h2>Permanently fixing locale problems</h2>
<p>The slower but superior fixes are when you may be able to yourself
fix the misconfiguration of your own environment variables.  The
mis(sing)configuration of the whole system's locales usually requires
the help of your friendly system administrator.</p>
<p>First, see earlier in this document about <a href="#Finding-locales">Finding locales</a>.  That tells
how to find which locales are really supported--and more importantly,
installed--on your system.  In our example error message, environment
variables affecting the locale are listed in the order of decreasing
importance (and unset variables do not matter).  Therefore, having
LC_ALL set to "En_US" must have been the bad choice, as shown by the
error message.  First try fixing locale settings listed first.</p>
<p>Second, if using the listed commands you see something <b>exactly</b>
(prefix matches do not count and case usually counts) like "En_US"
without the quotes, then you should be okay because you are using a
locale name that should be installed and available in your system.
In this case, see <a href="#Permanently-fixing-your-system's-locale-configuration">Permanently fixing your system's locale configuration</a>.</p>
<a name="Permanently-fixing-your-system's-locale-configuration"></a><h2>Permanently fixing your system's locale configuration</h2>
<p>This is when you see something like:</p>
<pre class="verbatim"><ol><li>	perl: warning: Please check that your locale settings:</li><li>	        LC_ALL = "En_US",</li><li>	        LANG = (unset)</li><li>	    are supported and installed on your system.</li></ol></pre><p>but then cannot see that "En_US" listed by the above-mentioned
commands.  You may see things like "en_US.ISO8859-1", but that isn't
the same.  In this case, try running under a locale
that you can list and which somehow matches what you tried.  The
rules for matching locale names are a bit vague because
standardization is weak in this area.  See again the
<a href="#Finding-locales">Finding locales</a> about general rules.</p>
<a name="Fixing-system-locale-configuration"></a><h2>Fixing system locale configuration</h2>
<p>Contact a system administrator (preferably your own) and report the exact
error message you get, and ask them to read this same documentation you
are now reading.  They should be able to check whether there is something
wrong with the locale configuration of the system.  The <a href="#Finding-locales">Finding locales</a>
section is unfortunately a bit vague about the exact commands and places
because these things are not that standardized.</p>
<a name="The-localeconv-function"></a><h2>The localeconv function</h2>
<p>The <code class="inline"><span class="i">POSIX::localeconv</span><span class="s">(</span><span class="s">)</span></code>
 function allows you to get particulars of the
locale-dependent numeric formatting information specified by the current
underlying <code class="inline"><span class="w">LC_NUMERIC</span></code>
 and <code class="inline"><span class="w">LC_MONETARY</span></code>
 locales (regardless of
whether called from within the scope of <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 or not).  (If
you just want the name of
the current locale for a particular category, use <code class="inline"><span class="i">POSIX::setlocale</span><span class="s">(</span><span class="s">)</span></code>

with a single parameter--see <a href="#The-setlocale-function">The setlocale function</a>.)</p>
<pre class="verbatim"><ol><li>        <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(locale_h)</span><span class="sc">;</span></li><li></li><li>        <span class="c"># Get a reference to a hash of locale-dependent info</span></li><li>        <span class="i">$locale_values</span> = <span class="i">localeconv</span><span class="s">(</span><span class="s">)</span><span class="sc">;</span></li><li></li><li>        <span class="c"># Output sorted list of the values</span></li><li>        for <span class="s">(</span><a class="l_k" href="functions/sort.html">sort</a> <a class="l_k" href="functions/keys.html">keys</a> <span class="i">%$locale_values</span><span class="s">)</span> <span class="s">{</span></li><li>            <a class="l_k" href="functions/printf.html">printf</a> <span class="q">&quot;%-20s = %s\n&quot;</span><span class="cm">,</span> <span class="i">$_</span><span class="cm">,</span> <span class="i">$locale_values</span>-&gt;{<span class="i">$_</span>}</li><li>        <span class="s">}</span></li></ol></pre><p><code class="inline"><span class="i">localeconv</span><span class="s">(</span><span class="s">)</span></code>
 takes no arguments, and returns <b>a reference to</b> a hash.
The keys of this hash are variable names for formatting, such as
<code class="inline"><span class="w">decimal_point</span></code>
 and <code class="inline"><span class="w">thousands_sep</span></code>
.  The values are the
corresponding, er, values.  See <a href="POSIX.html#localeconv">localeconv in POSIX</a> for a longer
example listing the categories an implementation might be expected to
provide; some provide more and others fewer.  You don't need an
explicit <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
, because <code class="inline"><span class="i">localeconv</span><span class="s">(</span><span class="s">)</span></code>
 always observes the
current locale.</p>
<p>Here's a simple-minded example program that rewrites its command-line
parameters as integers correctly formatted in the current locale:</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(locale_h)</span><span class="sc">;</span></li><li></li><li>    <span class="c"># Get some of locale&#39;s numeric formatting parameters</span></li><li>    <a class="l_k" href="functions/my.html">my</a> <span class="s">(</span><span class="i">$thousands_sep</span><span class="cm">,</span> <span class="i">$grouping</span><span class="s">)</span> =</li><li>            <span class="i">@</span>{<span class="i">localeconv</span><span class="s">(</span><span class="s">)</span>}{<span class="q">&#39;thousands_sep&#39;</span><span class="cm">,</span> <span class="q">&#39;grouping&#39;</span>}<span class="sc">;</span></li><li></li><li>    <span class="c"># Apply defaults if values are missing</span></li><li>    <span class="i">$thousands_sep</span> = <span class="q">&#39;,&#39;</span> <a class="l_k" href="functions/unless.html">unless</a> <span class="i">$thousands_sep</span><span class="sc">;</span></li><li></li><li>    <span class="c"># grouping and mon_grouping are packed lists</span></li><li>    <span class="c"># of small integers (characters) telling the</span></li><li>    <span class="c"># grouping (thousand_seps and mon_thousand_seps</span></li><li>    <span class="c"># being the group dividers) of numbers and</span></li><li>    <span class="c"># monetary quantities.  The integers&#39; meanings:</span></li><li>    <span class="c"># 255 means no more grouping, 0 means repeat</span></li><li>    <span class="c"># the previous grouping, 1-254 means use that</span></li><li>    <span class="c"># as the current grouping.  Grouping goes from</span></li><li>    <span class="c"># right to left (low to high digits).  In the</span></li><li>    <span class="c"># below we cheat slightly by never using anything</span></li><li>    <span class="c"># else than the first grouping (whatever that is).</span></li><li>    <a class="l_k" href="functions/if.html">if</a> <span class="s">(</span><span class="i">$grouping</span><span class="s">)</span> <span class="s">{</span></li><li>        <span class="i">@grouping</span> = <a class="l_k" href="functions/unpack.html">unpack</a><span class="s">(</span><span class="q">&quot;C*&quot;</span><span class="cm">,</span> <span class="i">$grouping</span><span class="s">)</span><span class="sc">;</span></li><li>    <span class="s">}</span> <a class="l_k" href="functions/else.html">else</a> <span class="s">{</span></li><li>        <span class="i">@grouping</span> = <span class="s">(</span><span class="n">3</span><span class="s">)</span><span class="sc">;</span></li><li>    <span class="s">}</span></li><li></li><li>    <span class="c"># Format command line params for current locale</span></li><li>    <a class="l_k" href="functions/for.html">for</a> <span class="s">(</span><span class="i">@ARGV</span><span class="s">)</span> <span class="s">{</span></li><li>        <span class="i">$_</span> = <a class="l_k" href="functions/int.html">int</a><span class="sc">;</span>    <span class="c"># Chop non-integer part</span></li><li>        <span class="n">1</span> <a class="l_k" href="functions/while.html">while</a></li><li>        <span class="q">s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;$_&quot;</span><span class="sc">;</span></li><li>    <span class="s">}</span></li><li>    <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;\n&quot;</span><span class="sc">;</span></li></ol></pre><p>Note that if the platform doesn't have <code class="inline"><span class="w">LC_NUMERIC</span></code>
 and/or
<code class="inline"><span class="w">LC_MONETARY</span></code>
 available or enabled, the corresponding elements of the
hash will be missing.</p>
<a name="I18N%3a%3aLanginfo"></a><h2>I18N::Langinfo</h2>
<p>Another interface for querying locale-dependent information is the
<code class="inline"><span class="i">I18N::Langinfo::langinfo</span><span class="s">(</span><span class="s">)</span></code>
 function, available at least in Unix-like
systems and VMS.</p>
<p>The following example will import the <code class="inline"><span class="i">langinfo</span><span class="s">(</span><span class="s">)</span></code>
 function itself and
three constants to be used as arguments to <code class="inline"><span class="i">langinfo</span><span class="s">(</span><span class="s">)</span></code>
: a constant for
the abbreviated first day of the week (the numbering starts from
Sunday = 1) and two more constants for the affirmative and negative
answers for a yes/no question in the current locale.</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/use.html">use</a> <span class="w">I18N::Langinfo</span> <span class="q">qw(langinfo ABDAY_1 YESSTR NOSTR)</span><span class="sc">;</span></li><li></li><li>    <a class="l_k" href="functions/my.html">my</a> <span class="s">(</span><span class="i">$abday_1</span><span class="cm">,</span> <span class="i">$yesstr</span><span class="cm">,</span> <span class="i">$nostr</span><span class="s">)</span></li><li>                = <a class="l_k" href="functions/map.html">map</a> <span class="s">{</span> <span class="w">langinfo</span> <span class="s">}</span> <span class="q">qw(ABDAY_1 YESSTR NOSTR)</span><span class="sc">;</span></li><li></li><li>    <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;$abday_1? [$yesstr/$nostr] &quot;</span><span class="sc">;</span></li></ol></pre><p>In other words, in the "C" (or English) locale the above will probably
print something like:</p>
<pre class="verbatim"><ol><li>    Sun? [yes/no]</li></ol></pre><p>See <a href="I18N/Langinfo.html">I18N::Langinfo</a> for more information.</p>
<a name="LOCALE-CATEGORIES"></a><h1>LOCALE CATEGORIES</h1>
<p>The following subsections describe basic locale categories.  Beyond these,
some combination categories allow manipulation of more than one
basic category at a time.  See <a href="#ENVIRONMENT">ENVIRONMENT</a> for a discussion of these.</p>
<a name="Category-LC_COLLATE%3a-Collation%3a-Text-Comparisons-and-Sorting"></a><h2>Category <code class="inline"><span class="w">LC_COLLATE</span></code>
: Collation: Text Comparisons and Sorting</h2>
<p>In the scope of a <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 form that includes collation, Perl
looks to the <code class="inline"><span class="w">LC_COLLATE</span></code>

environment variable to determine the application's notions on collation
(ordering) of characters.  For example, "b" follows "a" in Latin
alphabets, but where do "&#xe1;" and "&#xe5;" belong?  And while
"color" follows "chocolate" in English, what about in traditional Spanish?</p>
<p>The following collations all make sense and you may meet any of them
if you <code class="inline"><span class="q">&quot;use locale&quot;</span></code>
.</p>
<pre class="verbatim"><ol><li>	<span class="w">A</span> <span class="w">B</span> <span class="w">C</span> <span class="w">D</span> <span class="w">E</span> <span class="w">a</span> <span class="w">b</span> <span class="w">c</span> <span class="w">d</span> <span class="w">e</span></li><li>	<span class="w">A</span> <span class="w">a</span> <span class="w">B</span> <span class="w">b</span> <span class="w">C</span> <span class="w">c</span> <span class="w">D</span> <span class="w">d</span> <span class="w">E</span> <span class="w">e</span></li><li>	<span class="w">a</span> <span class="w">A</span> <span class="w">b</span> <span class="w">B</span> <span class="w">c</span> <span class="w">C</span> <span class="w">d</span> <span class="w">D</span> <span class="w">e</span> <span class="w">E</span></li><li>	<span class="w">a</span> <span class="w">b</span> <span class="w">c</span> <span class="w">d</span> <span class="w">e</span> <span class="w">A</span> <span class="w">B</span> <span class="w">C</span> <span class="w">D</span> <span class="w">E</span></li></ol></pre><p>Here is a code snippet to tell what "word"
characters are in the current locale, in that locale's order:</p>
<pre class="verbatim"><ol><li>        <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/print.html">print</a> +<span class="s">(</span><a class="l_k" href="functions/sort.html">sort</a> <a class="l_k" href="functions/grep.html">grep</a> <span class="q">/\w/</span><span class="cm">,</span> <a class="l_k" href="functions/map.html">map</a> <span class="s">{</span> <a class="l_k" href="functions/chr.html">chr</a> <span class="s">}</span> <span class="n">0</span>..<span class="n">255</span><span class="s">)</span><span class="cm">,</span> <span class="q">&quot;\n&quot;</span><span class="sc">;</span></li></ol></pre><p>Compare this with the characters that you see and their order if you
state explicitly that the locale should be ignored:</p>
<pre class="verbatim"><ol><li>        <a class="l_k" href="functions/no.html">no</a> <span class="w">locale</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/print.html">print</a> +<span class="s">(</span><a class="l_k" href="functions/sort.html">sort</a> <a class="l_k" href="functions/grep.html">grep</a> <span class="q">/\w/</span><span class="cm">,</span> <a class="l_k" href="functions/map.html">map</a> <span class="s">{</span> <a class="l_k" href="functions/chr.html">chr</a> <span class="s">}</span> <span class="n">0</span>..<span class="n">255</span><span class="s">)</span><span class="cm">,</span> <span class="q">&quot;\n&quot;</span><span class="sc">;</span></li></ol></pre><p>This machine-native collation (which is what you get unless <code class="inline"><a class="l_k" href="functions/use.html">use</a>
<span class="w">locale</span></code>
 has appeared earlier in the same block) must be used for
sorting raw binary data, whereas the locale-dependent collation of the
first example is useful for natural text.</p>
<p>As noted in <a href="#USING-LOCALES">USING LOCALES</a>, <code class="inline">cmp</code>
 compares according to the current
collation locale when <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 is in effect, but falls back to a
char-by-char comparison for strings that the locale says are equal. You
can use <code class="inline"><span class="i">POSIX::strcoll</span><span class="s">(</span><span class="s">)</span></code>
 if you don't want this fall-back:</p>
<pre class="verbatim"><ol><li>        <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(strcoll)</span><span class="sc">;</span></li><li>        <span class="i">$equal_in_locale</span> =</li><li>            !<span class="i">strcoll</span><span class="s">(</span><span class="q">&quot;space and case ignored&quot;</span><span class="cm">,</span> <span class="q">&quot;SpaceAndCaseIgnored&quot;</span><span class="s">)</span><span class="sc">;</span></li></ol></pre><p><code class="inline"><span class="i">$equal_in_locale</span></code>
 will be true if the collation locale specifies a
dictionary-like ordering that ignores space characters completely and
which folds case.</p>
<p>Perl uses the platform's C library collation functions <code class="inline"><span class="i">strcoll</span><span class="s">(</span><span class="s">)</span></code>
 and
<code class="inline"><span class="i">strxfrm</span><span class="s">(</span><span class="s">)</span></code>
.  That means you get whatever they give.  On some
platforms, these functions work well on UTF-8 locales, giving
a reasonable default collation for the code points that are important in
that locale.  (And if they aren't working well, the problem may only be
that the locale definition is deficient, so can be fixed by using a
better definition file.  Unicode's definitions (see <a href="#Freely-available-locale-definitions">Freely available locale definitions</a>) provide reasonable UTF-8 locale collation
definitions.)  Starting in Perl v5.26, Perl's use of these functions has
been made more seamless.  This may be sufficient for your needs.  For
more control, and to make sure strings containing any code point (not
just the ones important in the locale) collate properly, the
<a href="Unicode/Collate.html">Unicode::Collate</a> module is suggested.</p>
<p>In non-UTF-8 locales (hence single byte), code points above 0xFF are
technically invalid.  But if present, again starting in v5.26, they will
collate to the same position as the highest valid code point does.  This
generally gives good results, but the collation order may be skewed if
the valid code point gets special treatment when it forms particular
sequences with other characters as defined by the locale.
When two strings collate identically, the code point order is used as a
tie breaker.</p>
<p>If Perl detects that there are problems with the locale collation order,
it reverts to using non-locale collation rules for that locale.</p>
<p>If Perl detects that there are problems with the locale collation order,
it reverts to using non-locale collation rules for that locale.</p>
<p>If you have a single string that you want to check for "equality in
locale" against several others, you might think you could gain a little
efficiency by using <code class="inline"><span class="i">POSIX::strxfrm</span><span class="s">(</span><span class="s">)</span></code>
 in conjunction with <code class="inline">eq</code>
:</p>
<pre class="verbatim"><ol><li>        <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(strxfrm)</span><span class="sc">;</span></li><li>        <span class="i">$xfrm_string</span> = <span class="i">strxfrm</span><span class="s">(</span><span class="q">&quot;Mixed-case string&quot;</span><span class="s">)</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;locale collation ignores spaces\n&quot;</span></li><li>            if <span class="i">$xfrm_string</span> eq <span class="i">strxfrm</span><span class="s">(</span><span class="q">&quot;Mixed-casestring&quot;</span><span class="s">)</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;locale collation ignores hyphens\n&quot;</span></li><li>            if <span class="i">$xfrm_string</span> eq <span class="i">strxfrm</span><span class="s">(</span><span class="q">&quot;Mixedcase string&quot;</span><span class="s">)</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;locale collation ignores case\n&quot;</span></li><li>            if <span class="i">$xfrm_string</span> eq <span class="i">strxfrm</span><span class="s">(</span><span class="q">&quot;mixed-case string&quot;</span><span class="s">)</span><span class="sc">;</span></li></ol></pre><p><code class="inline"><span class="i">strxfrm</span><span class="s">(</span><span class="s">)</span></code>
 takes a string and maps it into a transformed string for use
in char-by-char comparisons against other transformed strings during
collation.  "Under the hood", locale-affected Perl comparison operators
call <code class="inline"><span class="i">strxfrm</span><span class="s">(</span><span class="s">)</span></code>
 for both operands, then do a char-by-char
comparison of the transformed strings.  By calling <code class="inline"><span class="i">strxfrm</span><span class="s">(</span><span class="s">)</span></code>
 explicitly
and using a non locale-affected comparison, the example attempts to save
a couple of transformations.  But in fact, it doesn't save anything: Perl
magic (see <a href="perlguts.html#Magic-Variables">Magic Variables in perlguts</a>) creates the transformed version of a
string the first time it's needed in a comparison, then keeps this version around
in case it's needed again.  An example rewritten the easy way with
<code class="inline">cmp</code>
 runs just about as fast.  It also copes with null characters
embedded in strings; if you call <code class="inline"><span class="i">strxfrm</span><span class="s">(</span><span class="s">)</span></code>
 directly, it treats the first
null it finds as a terminator.  don't expect the transformed strings
it produces to be portable across systems--or even from one revision
of your operating system to the next.  In short, don't call <code class="inline"><span class="i">strxfrm</span><span class="s">(</span><span class="s">)</span></code>

directly: let Perl do it for you.</p>
<p>Note: <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 isn't shown in some of these examples because it isn't
needed: <code class="inline"><span class="i">strcoll</span><span class="s">(</span><span class="s">)</span></code>
 and <code class="inline"><span class="i">strxfrm</span><span class="s">(</span><span class="s">)</span></code>
 are POSIX functions
which use the standard system-supplied <code class="inline"><span class="w">libc</span></code>
 functions that
always obey the current <code class="inline"><span class="w">LC_COLLATE</span></code>
 locale.</p>
<a name="Category-LC_CTYPE%3a-Character-Types"></a><h2>Category <code class="inline"><span class="w">LC_CTYPE</span></code>
: Character Types</h2>
<p>In the scope of a <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 form that includes <code class="inline"><span class="w">LC_CTYPE</span></code>
, Perl
obeys the <code class="inline"><span class="w">LC_CTYPE</span></code>
 locale
setting.  This controls the application's notion of which characters are
alphabetic, numeric, punctuation, <i>etc</i>.  This affects Perl's <code class="inline">\<span class="w">w</span></code>

regular expression metanotation,
which stands for alphanumeric characters--that is, alphabetic,
numeric, and the platform's native underscore.
(Consult <a href="perlre.html">perlre</a> for more information about
regular expressions.)  Thanks to <code class="inline"><span class="w">LC_CTYPE</span></code>
, depending on your locale
setting, characters like "&#xe6;", "&#xf0;", "&#xdf;", and
"&#xf8;" may be understood as <code class="inline">\<span class="w">w</span></code>
 characters.
It also affects things like <code class="inline">\s</code>, <code class="inline">\<span class="w">D</span></code>
, and the POSIX character
classes, like <code class="inline"><span class="s">[</span><span class="s">[</span><span class="co">:</span><span class="w">graph</span><span class="co">:</span><span class="s">]</span><span class="s">]</span></code>
.  (See <a href="perlrecharclass.html">perlrecharclass</a> for more
information on all these.)</p>
<p>The <code class="inline"><span class="w">LC_CTYPE</span></code>
 locale also provides the map used in transliterating
characters between lower and uppercase.  This affects the case-mapping
functions--<code class="inline"><a class="l_k" href="functions/fc.html">fc()</a></code>, <code class="inline"><a class="l_k" href="functions/lc.html">lc()</a></code>, <code class="inline"><a class="l_k" href="functions/lcfirst.html">lcfirst()</a></code>, <code class="inline"><a class="l_k" href="functions/uc.html">uc()</a></code>, and <code class="inline"><a class="l_k" href="functions/ucfirst.html">ucfirst()</a></code>;
case-mapping
interpolation with <code class="inline">\<span class="w">F</span></code>
, <code class="inline">\<span class="w">l</span></code>
, <code class="inline">\<span class="w">L</span></code>
, <code class="inline">\<span class="w">u</span></code>
, or <code class="inline">\<span class="w">U</span></code>
 in double-quoted
strings and <code class="inline"><a class="l_k" href="functions/s.html">s///</a></code> substitutions; and case-independent regular expression
pattern matching using the <code class="inline"><span class="w">i</span></code>
 modifier.</p>
<p>Starting in v5.20, Perl supports UTF-8 locales for <code class="inline"><span class="w">LC_CTYPE</span></code>
, but
otherwise Perl only supports single-byte locales, such as the ISO 8859
series.  This means that wide character locales, for example for Asian
languages, are not well-supported.  Use of these locales may cause core
dumps.  If the platform has the capability for Perl to detect such a
locale, starting in Perl v5.22, <a href="warnings.html#Category-Hierarchy">Perl will warn, default enabled</a>, using the <code class="inline"><span class="w">locale</span></code>
 warning
category, whenever such a locale is switched into.  The UTF-8 locale
support is actually a
superset of POSIX locales, because it is really full Unicode behavior
as if no <code class="inline"><span class="w">LC_CTYPE</span></code>
 locale were in effect at all (except for tainting;
see <a href="#SECURITY">SECURITY</a>).  POSIX locales, even UTF-8 ones,
are lacking certain concepts in Unicode, such as the idea that changing
the case of a character could expand to be more than one character.
Perl in a UTF-8 locale, will give you that expansion.  Prior to v5.20,
Perl treated a UTF-8 locale on some platforms like an ISO 8859-1 one,
with some restrictions, and on other platforms more like the "C" locale.
For releases v5.16 and v5.18, <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span> <span class="q">&#39;not_characters</span></code>
 could be
used as a workaround for this (see <a href="#Unicode-and-UTF-8">Unicode and UTF-8</a>).</p>
<p>Note that there are quite a few things that are unaffected by the
current locale.  Any literal character is the native character for the
given platform.  Hence 'A' means the character at code point 65 on ASCII
platforms, and 193 on EBCDIC.  That may or may not be an 'A' in the
current locale, if that locale even has an 'A'.
Similarly, all the escape sequences for particular characters,
<code class="inline">\<span class="w">n</span></code>
 for example, always mean the platform's native one.  This means,
for example, that <code class="inline">\<span class="w">N</span></code>
 in regular expressions (every character
but new-line) works on the platform character set.</p>
<p>Starting in v5.22, Perl will by default warn when switching into a
locale that redefines any ASCII printable character (plus <code class="inline">\<span class="w">t</span></code>
 and
<code class="inline">\<span class="w">n</span></code>
) into a different class than expected.  This is likely to
happen on modern locales only on EBCDIC platforms, where, for example,
a CCSID 0037 locale on a CCSID 1047 machine moves <code class="inline"><span class="q">&quot;[&quot;</span></code>
, but it can
happen on ASCII platforms with the ISO 646 and other
7-bit locales that are essentially obsolete.  Things may still work,
depending on what features of Perl are used by the program.  For
example, in the example from above where <code class="inline"><span class="q">&quot;|&quot;</span></code>
 becomes a <code class="inline">\<span class="w">w</span></code>
, and
there are no regular expressions where this matters, the program may
still work properly.  The warning lists all the characters that
it can determine could be adversely affected.</p>
<p><b>Note:</b> A broken or malicious <code class="inline"><span class="w">LC_CTYPE</span></code>
 locale definition may result
in clearly ineligible characters being considered to be alphanumeric by
your application.  For strict matching of (mundane) ASCII letters and
digits--for example, in command strings--locale-aware applications
should use <code class="inline">\<span class="w">w</span></code>
 with the <code class="inline"><span class="q">/a</span></code>
 regular expression modifier.  See <a href="#SECURITY">SECURITY</a>.</p>
<a name="Category-LC_NUMERIC%3a-Numeric-Formatting"></a><h2>Category <code class="inline"><span class="w">LC_NUMERIC</span></code>
: Numeric Formatting</h2>
<p>After a proper <code class="inline"><span class="i">POSIX::setlocale</span><span class="s">(</span><span class="s">)</span></code>
 call, and within the scope of
of a <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 form that includes numerics, Perl obeys the
<code class="inline"><span class="w">LC_NUMERIC</span></code>
 locale information, which controls an application's idea
of how numbers should be formatted for human readability.
In most implementations the only effect is to
change the character used for the decimal point--perhaps from "."  to ",".
The functions aren't aware of such niceties as thousands separation and
so on. (See <a href="#The-localeconv-function">The localeconv function</a> if you care about these things.)</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(strtod setlocale LC_NUMERIC)</span><span class="sc">;</span></li><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span><span class="sc">;</span></li><li></li><li> <span class="w">setlocale</span> <span class="w">LC_NUMERIC</span><span class="cm">,</span> <span class="q">&quot;&quot;</span><span class="sc">;</span></li><li></li><li> <span class="i">$n</span> = <span class="n">5</span>/<span class="n">2</span><span class="sc">;</span>   <span class="c"># Assign numeric 2.5 to $n</span></li><li></li><li> <span class="i">$a</span> = <span class="q">&quot; $n&quot;</span><span class="sc">;</span> <span class="c"># Locale-dependent conversion to string</span></li><li></li><li> <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;half five is $n\n&quot;</span><span class="sc">;</span>       <span class="c"># Locale-dependent output</span></li><li></li><li> <a class="l_k" href="functions/printf.html">printf</a> <span class="q">&quot;half five is %g\n&quot;</span><span class="cm">,</span> <span class="i">$n</span><span class="sc">;</span>  <span class="c"># Locale-dependent output</span></li><li></li><li> <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;DECIMAL POINT IS COMMA\n&quot;</span></li><li>          <a class="l_k" href="functions/if.html">if</a> <span class="i">$n</span> == <span class="s">(</span><span class="i">strtod</span><span class="s">(</span><span class="q">&quot;2,5&quot;</span><span class="s">)</span><span class="s">)</span>[<span class="n">0</span>]<span class="sc">;</span> <span class="c"># Locale-dependent conversion</span></li></ol></pre><p>See also <a href="I18N/Langinfo.html">I18N::Langinfo</a> and <code class="inline"><span class="w">RADIXCHAR</span></code>
.</p>
<a name="Category-LC_MONETARY%3a-Formatting-of-monetary-amounts"></a><h2>Category <code class="inline"><span class="w">LC_MONETARY</span></code>
: Formatting of monetary amounts</h2>
<p>The C standard defines the <code class="inline"><span class="w">LC_MONETARY</span></code>
 category, but not a function
that is affected by its contents.  (Those with experience of standards
committees will recognize that the working group decided to punt on the
issue.)  Consequently, Perl essentially takes no notice of it.  If you
really want to use <code class="inline"><span class="w">LC_MONETARY</span></code>
, you can query its contents--see
<a href="#The-localeconv-function">The localeconv function</a>--and use the information that it returns in your
application's own formatting of currency amounts.  However, you may well
find that the information, voluminous and complex though it may be, still
does not quite meet your requirements: currency formatting is a hard nut
to crack.</p>
<p>See also <a href="I18N/Langinfo.html">I18N::Langinfo</a> and <code class="inline"><span class="w">CRNCYSTR</span></code>
.</p>
<a name="Category-LC_TIME%3a-Respresentation-of-time"></a><h2>Category <code class="inline"><span class="w">LC_TIME</span></code>
: Respresentation of time</h2>
<p>Output produced by <code class="inline"><span class="i">POSIX::strftime</span><span class="s">(</span><span class="s">)</span></code>
, which builds a formatted
human-readable date/time string, is affected by the current <code class="inline"><span class="w">LC_TIME</span></code>

locale.  Thus, in a French locale, the output produced by the <code class="inline"><span class="i">%B</span></code>

format element (full month name) for the first month of the year would
be "janvier".  Here's how to get a list of long month names in the
current locale:</p>
<pre class="verbatim"><ol><li>        <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(strftime)</span><span class="sc">;</span></li><li>        for <span class="s">(</span><span class="n">0</span>..<span class="n">11</span><span class="s">)</span> <span class="s">{</span></li><li>            <span class="i">$long_month_name</span>[<span class="i">$_</span>] =</li><li>                <span class="i">strftime</span><span class="s">(</span><span class="q">&quot;%B&quot;</span><span class="cm">,</span> <span class="n">0</span><span class="cm">,</span> <span class="n">0</span><span class="cm">,</span> <span class="n">0</span><span class="cm">,</span> <span class="n">1</span><span class="cm">,</span> <span class="i">$_</span><span class="cm">,</span> <span class="n">96</span><span class="s">)</span><span class="sc">;</span></li><li>        <span class="s">}</span></li></ol></pre><p>Note: <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 isn't needed in this example: <code class="inline"><span class="i">strftime</span><span class="s">(</span><span class="s">)</span></code>
 is a POSIX
function which uses the standard system-supplied <code class="inline"><span class="w">libc</span></code>
 function that
always obeys the current <code class="inline"><span class="w">LC_TIME</span></code>
 locale.</p>
<p>See also <a href="I18N/Langinfo.html">I18N::Langinfo</a> and <code class="inline"><span class="w">ABDAY_1</span></code>
..<code class="inline"><span class="w">ABDAY_7</span></code>
, <code class="inline"><span class="w">DAY_1</span></code>
..<code class="inline"><span class="w">DAY_7</span></code>
,
<code class="inline"><span class="w">ABMON_1</span></code>
..<code class="inline"><span class="w">ABMON_12</span></code>
, and <code class="inline"><span class="w">ABMON_1</span></code>
..<code class="inline"><span class="w">ABMON_12</span></code>
.</p>
<a name="Other-categories"></a><h2>Other categories</h2>
<p>The remaining locale categories are not currently used by Perl itself.
But again note that things Perl interacts with may use these, including
extensions outside the standard Perl distribution, and by the
operating system and its utilities.  Note especially that the string
value of <code class="inline"><span class="i">$!</span></code>
 and the error messages given by external utilities may
be changed by <code class="inline"><span class="w">LC_MESSAGES</span></code>
.  If you want to have portable error
codes, use <code class="inline"><span class="i">%!</span></code>
.  See <a href="Errno.html">Errno</a>.</p>
<a name="SECURITY"></a><h1>SECURITY</h1>
<p>Although the main discussion of Perl security issues can be found in
<a href="perlsec.html">perlsec</a>, a discussion of Perl's locale handling would be incomplete
if it did not draw your attention to locale-dependent security issues.
Locales--particularly on systems that allow unprivileged users to
build their own locales--are untrustworthy.  A malicious (or just plain
broken) locale can make a locale-aware application give unexpected
results.  Here are a few possibilities:</p>
<ul>
<li>
<p>Regular expression checks for safe file names or mail addresses using
<code class="inline">\<span class="w">w</span></code>
 may be spoofed by an <code class="inline"><span class="w">LC_CTYPE</span></code>
 locale that claims that
characters such as <code class="inline"><span class="q">&quot;&gt;&quot;</span></code>
 and <code class="inline"><span class="q">&quot;|&quot;</span></code>
 are alphanumeric.</p>
</li>
<li>
<p>String interpolation with case-mapping, as in, say, <code class="inline"><span class="i">$dest</span> =
<span class="q">&quot;C:\U$name.$ext&quot;</span></code>
, may produce dangerous results if a bogus <code class="inline"><span class="w">LC_CTYPE</span></code>

case-mapping table is in effect.</p>
</li>
<li>
<p>A sneaky <code class="inline"><span class="w">LC_COLLATE</span></code>
 locale could result in the names of students with
"D" grades appearing ahead of those with "A"s.</p>
</li>
<li>
<p>An application that takes the trouble to use information in
<code class="inline"><span class="w">LC_MONETARY</span></code>
 may format debits as if they were credits and vice versa
if that locale has been subverted.  Or it might make payments in US
dollars instead of Hong Kong dollars.</p>
</li>
<li>
<p>The date and day names in dates formatted by <code class="inline"><span class="i">strftime</span><span class="s">(</span><span class="s">)</span></code>
 could be
manipulated to advantage by a malicious user able to subvert the
<code class="inline"><span class="w">LC_DATE</span></code>
 locale.  ("Look--it says I wasn't in the building on
Sunday.")</p>
</li>
</ul>
<p>Such dangers are not peculiar to the locale system: any aspect of an
application's environment which may be modified maliciously presents
similar challenges.  Similarly, they are not specific to Perl: any
programming language that allows you to write programs that take
account of their environment exposes you to these issues.</p>
<p>Perl cannot protect you from all possibilities shown in the
examples--there is no substitute for your own vigilance--but, when
<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 is in effect, Perl uses the tainting mechanism (see
<a href="perlsec.html">perlsec</a>) to mark string results that become locale-dependent, and
which may be untrustworthy in consequence.  Here is a summary of the
tainting behavior of operators and functions that may be affected by
the locale:</p>
<ul>
<li>
<p><b>Comparison operators</b> (<code class="inline">lt</code>
, <code class="inline">le</code>
, <code class="inline">ge</code>
, <code class="inline">gt</code>
 and <code class="inline">cmp</code>
):</p>
<p>Scalar true/false (or less/equal/greater) result is never tainted.</p>
</li>
<li>
<p><b>Case-mapping interpolation</b> (with <code class="inline">\<span class="w">l</span></code>
, <code class="inline">\<span class="w">L</span></code>
, <code class="inline">\<span class="w">u</span></code>
, <code class="inline">\<span class="w">U</span></code>
, or <code class="inline">\<span class="w">F</span></code>
)</p>
<p>The result string containing interpolated material is tainted if
a <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 form that includes <code class="inline"><span class="w">LC_CTYPE</span></code>
 is in effect.</p>
</li>
<li>
<p><b>Matching operator</b> (<code class="inline"><a class="l_k" href="functions/m.html">m//</a></code>):</p>
<p>Scalar true/false result never tainted.</p>
<p>All subpatterns, either delivered as a list-context result or as <code class="inline"><span class="i">$1</span></code>

<i>etc</i>., are tainted if a <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 form that includes
<code class="inline"><span class="w">LC_CTYPE</span></code>
 is in effect, and the subpattern
regular expression contains a locale-dependent construct.  These
constructs include <code class="inline">\<span class="w">w</span></code>
 (to match an alphanumeric character), <code class="inline">\<span class="w">W</span></code>

(non-alphanumeric character), <code class="inline">\<span class="w">b</span></code>
 and <code class="inline">\<span class="w">B</span></code>
 (word-boundary and
non-boundardy, which depend on what <code class="inline">\<span class="w">w</span></code>
 and <code class="inline">\<span class="w">W</span></code>
 match), <code class="inline">\s</code>
(whitespace character), <code class="inline">\<span class="w">S</span></code>
 (non whitespace character), <code class="inline">\<span class="w">d</span></code>
 and
<code class="inline">\<span class="w">D</span></code>
 (digits and non-digits), and the POSIX character classes, such as
<code class="inline">[:alpha:]</code> (see <a href="perlrecharclass.html#POSIX-Character-Classes">POSIX Character Classes in perlrecharclass</a>).</p>
<p>Tainting is also likely if the pattern is to be matched
case-insensitively (via <code class="inline">/i</code>).  The exception is if all the code points
to be matched this way are above 255 and do not have folds under Unicode
rules to below 256.  Tainting is not done for these because Perl
only uses Unicode rules for such code points, and those rules are the
same no matter what the current locale.</p>
<p>The matched-pattern variables, <code class="inline"><span class="i">$&amp;</span></code>
, <code class="inline"><span class="i">$`</span></code>
 (pre-match), <code class="inline"><span class="i">$&#39;</span></code>

(post-match), and <code class="inline"><span class="i">$+</span></code>
 (last match) also are tainted.</p>
</li>
<li>
<p><b>Substitution operator</b> (<code class="inline"><a class="l_k" href="functions/s.html">s///</a></code>):</p>
<p>Has the same behavior as the match operator.  Also, the left
operand of <code class="inline">=~</code>
 becomes tainted when a <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>

form that includes <code class="inline"><span class="w">LC_CTYPE</span></code>
 is in effect, if modified as
a result of a substitution based on a regular
expression match involving any of the things mentioned in the previous
item, or of case-mapping, such as <code class="inline">\<span class="w">l</span></code>
, <code class="inline">\<span class="w">L</span></code>
,<code class="inline">\<span class="w">u</span></code>
, <code class="inline">\<span class="w">U</span></code>
, or <code class="inline">\<span class="w">F</span></code>
.</p>
</li>
<li>
<p><b>Output formatting functions</b> (<code class="inline"><a class="l_k" href="functions/printf.html">printf()</a></code> and <code class="inline"><a class="l_k" href="functions/write.html">write()</a></code>):</p>
<p>Results are never tainted because otherwise even output from print,
for example <code class="inline"><a class="l_k" href="functions/print.html">print(1/7)</a></code>, should be tainted if <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 is in
effect.</p>
</li>
<li>
<p><b>Case-mapping functions</b> (<code class="inline"><a class="l_k" href="functions/lc.html">lc()</a></code>, <code class="inline"><a class="l_k" href="functions/lcfirst.html">lcfirst()</a></code>, <code class="inline"><a class="l_k" href="functions/uc.html">uc()</a></code>, <code class="inline"><a class="l_k" href="functions/ucfirst.html">ucfirst()</a></code>):</p>
<p>Results are tainted if a <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 form that includes <code class="inline"><span class="w">LC_CTYPE</span></code>
 is
in effect.</p>
</li>
<li>
<p><b>POSIX locale-dependent functions</b> (<code class="inline"><span class="i">localeconv</span><span class="s">(</span><span class="s">)</span></code>
, <code class="inline"><span class="i">strcoll</span><span class="s">(</span><span class="s">)</span></code>
,
<code class="inline"><span class="i">strftime</span><span class="s">(</span><span class="s">)</span></code>
, <code class="inline"><span class="i">strxfrm</span><span class="s">(</span><span class="s">)</span></code>
):</p>
<p>Results are never tainted.</p>
</li>
</ul>
<p>Three examples illustrate locale-dependent tainting.
The first program, which ignores its locale, won't run: a value taken
directly from the command line may not be used to name an output file
when taint checks are enabled.</p>
<pre class="verbatim"><ol><li>        <span class="c">#/usr/local/bin/perl -T</span></li><li>        <span class="c"># Run with taint checking</span></li><li></li><li>        <span class="c"># Command line sanity check omitted...</span></li><li>        <span class="i">$tainted_output_file</span> = <a class="l_k" href="functions/shift.html">shift</a><span class="sc">;</span></li><li></li><li>        <a class="l_k" href="functions/open.html">open</a><span class="s">(</span><span class="w">F</span><span class="cm">,</span> <span class="q">&quot;&gt;$tainted_output_file&quot;</span><span class="s">)</span></li><li>            <a class="l_k" href="functions/or.html">or</a> <a class="l_k" href="functions/warn.html">warn</a> <span class="q">&quot;Open of $tainted_output_file failed: $!\n&quot;</span><span class="sc">;</span></li></ol></pre><p>The program can be made to run by "laundering" the tainted value through
a regular expression: the second example--which still ignores locale
information--runs, creating the file named on its command line
if it can.</p>
<pre class="verbatim"><ol><li>        <span class="c">#/usr/local/bin/perl -T</span></li><li></li><li>        <span class="i">$tainted_output_file</span> = <a class="l_k" href="functions/shift.html">shift</a><span class="sc">;</span></li><li>        <span class="i">$tainted_output_file</span> =~ <span class="q">m%[\w/]+%</span><span class="sc">;</span></li><li>        <span class="i">$untainted_output_file</span> = <span class="i">$&amp;</span><span class="sc">;</span></li><li></li><li>        <a class="l_k" href="functions/open.html">open</a><span class="s">(</span><span class="w">F</span><span class="cm">,</span> <span class="q">&quot;&gt;$untainted_output_file&quot;</span><span class="s">)</span></li><li>            or <a class="l_k" href="functions/warn.html">warn</a> <span class="q">&quot;Open of $untainted_output_file failed: $!\n&quot;</span><span class="sc">;</span></li></ol></pre><p>Compare this with a similar but locale-aware program:</p>
<pre class="verbatim"><ol><li>        <span class="c">#/usr/local/bin/perl -T</span></li><li></li><li>        <span class="i">$tainted_output_file</span> = <a class="l_k" href="functions/shift.html">shift</a><span class="sc">;</span></li><li>        <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span><span class="sc">;</span></li><li>        <span class="i">$tainted_output_file</span> =~ <span class="q">m%[\w/]+%</span><span class="sc">;</span></li><li>        <span class="i">$localized_output_file</span> = <span class="i">$&amp;</span><span class="sc">;</span></li><li></li><li>        <a class="l_k" href="functions/open.html">open</a><span class="s">(</span><span class="w">F</span><span class="cm">,</span> <span class="q">&quot;&gt;$localized_output_file&quot;</span><span class="s">)</span></li><li>            or <a class="l_k" href="functions/warn.html">warn</a> <span class="q">&quot;Open of $localized_output_file failed: $!\n&quot;</span><span class="sc">;</span></li></ol></pre><p>This third program fails to run because <code class="inline"><span class="i">$&amp;</span></code>
 is tainted: it is the result
of a match involving <code class="inline">\<span class="w">w</span></code>
 while <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 is in effect.</p>
<a name="ENVIRONMENT"></a><h1>ENVIRONMENT</h1>
<ul>
<li><a name="PERL_SKIP_LOCALE_INIT"></a><b>PERL_SKIP_LOCALE_INIT</b>
<p>This environment variable, available starting in Perl v5.20, if set
(to any value), tells Perl to not use the rest of the
environment variables to initialize with.  Instead, Perl uses whatever
the current locale settings are.  This is particularly useful in
embedded environments, see
<a href="perlembed.html#Using-embedded-Perl-with-POSIX-locales">Using embedded Perl with POSIX locales in perlembed</a>.</p>
</li>
<li><a name="PERL_BADLANG"></a><b>PERL_BADLANG</b>
<p>A string that can suppress Perl's warning about failed locale settings
at startup.  Failure can occur if the locale support in the operating
system is lacking (broken) in some way--or if you mistyped the name of
a locale when you set up your environment.  If this environment
variable is absent, or has a value other than "0" or "", Perl will
complain about locale setting failures.</p>
<p><b>NOTE</b>: <code class="inline"><span class="w">PERL_BADLANG</span></code>
 only gives you a way to hide the warning message.
The message tells about some problem in your system's locale support,
and you should investigate what the problem is.</p>
</li>
</ul>
<p>The following environment variables are not specific to Perl: They are
part of the standardized (ISO C, XPG4, POSIX 1.c) <code class="inline"><span class="i">setlocale</span><span class="s">(</span><span class="s">)</span></code>
 method
for controlling an application's opinion on data.  Windows is non-POSIX,
but Perl arranges for the following to work as described anyway.
If the locale given by an environment variable is not valid, Perl tries
the next lower one in priority.  If none are valid, on Windows, the
system default locale is then tried.  If all else fails, the <code class="inline"><span class="q">&quot;C&quot;</span></code>

locale is used.  If even that doesn't work, something is badly broken,
but Perl tries to forge ahead with whatever the locale settings might
be.</p>
<ul>
<li><a name="LC_ALL"></a><b><code class="inline"><span class="w">LC_ALL</span></code>
</b>
<p><code class="inline"><span class="w">LC_ALL</span></code>
 is the "override-all" locale environment variable. If
set, it overrides all the rest of the locale environment variables.</p>
</li>
<li><a name="LANGUAGE"></a><b><code class="inline"><span class="w">LANGUAGE</span></code>
</b>
<p><b>NOTE</b>: <code class="inline"><span class="w">LANGUAGE</span></code>
 is a GNU extension, it affects you only if you
are using the GNU libc.  This is the case if you are using e.g. Linux.
If you are using "commercial" Unixes you are most probably <i>not</i>
using GNU libc and you can ignore <code class="inline"><span class="w">LANGUAGE</span></code>
.</p>
<p>However, in the case you are using <code class="inline"><span class="w">LANGUAGE</span></code>
: it affects the
language of informational, warning, and error messages output by
commands (in other words, it's like <code class="inline"><span class="w">LC_MESSAGES</span></code>
) but it has higher
priority than <code class="inline"><span class="w">LC_ALL</span></code>
.  Moreover, it's not a single value but
instead a "path" (":"-separated list) of <i>languages</i> (not locales).
See the GNU <code class="inline"><span class="w">gettext</span></code>
 library documentation for more information.</p>
</li>
<li><a name="LC_CTYPE"></a><b><code class="inline"><span class="w">LC_CTYPE</span></code>
</b>
<p>In the absence of <code class="inline"><span class="w">LC_ALL</span></code>
, <code class="inline"><span class="w">LC_CTYPE</span></code>
 chooses the character type
locale.  In the absence of both <code class="inline"><span class="w">LC_ALL</span></code>
 and <code class="inline"><span class="w">LC_CTYPE</span></code>
, <code class="inline"><span class="w">LANG</span></code>

chooses the character type locale.</p>
</li>
<li><a name="LC_COLLATE"></a><b><code class="inline"><span class="w">LC_COLLATE</span></code>
</b>
<p>In the absence of <code class="inline"><span class="w">LC_ALL</span></code>
, <code class="inline"><span class="w">LC_COLLATE</span></code>
 chooses the collation
(sorting) locale.  In the absence of both <code class="inline"><span class="w">LC_ALL</span></code>
 and <code class="inline"><span class="w">LC_COLLATE</span></code>
,
<code class="inline"><span class="w">LANG</span></code>
 chooses the collation locale.</p>
</li>
<li><a name="LC_MONETARY"></a><b><code class="inline"><span class="w">LC_MONETARY</span></code>
</b>
<p>In the absence of <code class="inline"><span class="w">LC_ALL</span></code>
, <code class="inline"><span class="w">LC_MONETARY</span></code>
 chooses the monetary
formatting locale.  In the absence of both <code class="inline"><span class="w">LC_ALL</span></code>
 and <code class="inline"><span class="w">LC_MONETARY</span></code>
,
<code class="inline"><span class="w">LANG</span></code>
 chooses the monetary formatting locale.</p>
</li>
<li><a name="LC_NUMERIC"></a><b><code class="inline"><span class="w">LC_NUMERIC</span></code>
</b>
<p>In the absence of <code class="inline"><span class="w">LC_ALL</span></code>
, <code class="inline"><span class="w">LC_NUMERIC</span></code>
 chooses the numeric format
locale.  In the absence of both <code class="inline"><span class="w">LC_ALL</span></code>
 and <code class="inline"><span class="w">LC_NUMERIC</span></code>
, <code class="inline"><span class="w">LANG</span></code>

chooses the numeric format.</p>
</li>
<li><a name="LC_TIME"></a><b><code class="inline"><span class="w">LC_TIME</span></code>
</b>
<p>In the absence of <code class="inline"><span class="w">LC_ALL</span></code>
, <code class="inline"><span class="w">LC_TIME</span></code>
 chooses the date and time
formatting locale.  In the absence of both <code class="inline"><span class="w">LC_ALL</span></code>
 and <code class="inline"><span class="w">LC_TIME</span></code>
,
<code class="inline"><span class="w">LANG</span></code>
 chooses the date and time formatting locale.</p>
</li>
<li><a name="LANG"></a><b><code class="inline"><span class="w">LANG</span></code>
</b>
<p><code class="inline"><span class="w">LANG</span></code>
 is the "catch-all" locale environment variable. If it is set, it
is used as the last resort after the overall <code class="inline"><span class="w">LC_ALL</span></code>
 and the
category-specific <code class="inline">LC_<i>foo</i></code>.</p>
</li>
</ul>
<a name="Examples"></a><h2>Examples</h2>
<p>The <code class="inline"><span class="w">LC_NUMERIC</span></code>
 controls the numeric output:</p>
<pre class="verbatim"><ol><li>   <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span><span class="sc">;</span></li><li>   <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(locale_h)</span><span class="sc">;</span> <span class="c"># Imports setlocale() and the LC_ constants.</span></li><li>   <span class="i">setlocale</span><span class="s">(</span><span class="w">LC_NUMERIC</span><span class="cm">,</span> <span class="q">&quot;fr_FR&quot;</span><span class="s">)</span> <a class="l_k" href="functions/or.html">or</a> <a class="l_k" href="functions/die.html">die</a> <span class="q">&quot;Pardon&quot;</span><span class="sc">;</span></li><li>   <a class="l_k" href="functions/printf.html">printf</a> <span class="q">&quot;%g\n&quot;</span><span class="cm">,</span> <span class="n">1.23</span><span class="sc">;</span> <span class="c"># If the &quot;fr_FR&quot; succeeded, probably shows 1,23.</span></li></ol></pre><p>and also how strings are parsed by <code class="inline"><span class="i">POSIX::strtod</span><span class="s">(</span><span class="s">)</span></code>
 as numbers:</p>
<pre class="verbatim"><ol><li>   <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span><span class="sc">;</span></li><li>   <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(locale_h strtod)</span><span class="sc">;</span></li><li>   <span class="i">setlocale</span><span class="s">(</span><span class="w">LC_NUMERIC</span><span class="cm">,</span> <span class="q">&quot;de_DE&quot;</span><span class="s">)</span> <a class="l_k" href="functions/or.html">or</a> <a class="l_k" href="functions/die.html">die</a> <span class="q">&quot;Entschuldigung&quot;</span><span class="sc">;</span></li><li>   <a class="l_k" href="functions/my.html">my</a> <span class="i">$x</span> = <span class="i">strtod</span><span class="s">(</span><span class="q">&quot;2,34&quot;</span><span class="s">)</span> + <span class="n">5</span><span class="sc">;</span></li><li>   <a class="l_k" href="functions/print.html">print</a> <span class="i">$x</span><span class="cm">,</span> <span class="q">&quot;\n&quot;</span><span class="sc">;</span> <span class="c"># Probably shows 7,34.</span></li></ol></pre><a name="NOTES"></a><h1>NOTES</h1>
<a name="String-eval-and-LC_NUMERIC"></a><h2>String <code class="inline"><a class="l_k" href="functions/eval.html">eval</a></code> and <code class="inline"><span class="w">LC_NUMERIC</span></code>
</h2>
<p>A string <a href="functions/eval.html">eval EXPR</a> parses its expression as standard
Perl.  It is therefore expecting the decimal point to be a dot.  If
<code class="inline"><span class="w">LC_NUMERIC</span></code>
 is set to have this be a comma instead, the parsing will
be confused, perhaps silently.</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span><span class="sc">;</span></li><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">POSIX</span> <span class="q">qw(locale_h)</span><span class="sc">;</span></li><li> <span class="i">setlocale</span><span class="s">(</span><span class="w">LC_NUMERIC</span><span class="cm">,</span> <span class="q">&quot;fr_FR&quot;</span><span class="s">)</span> <a class="l_k" href="functions/or.html">or</a> <a class="l_k" href="functions/die.html">die</a> <span class="q">&quot;Pardon&quot;</span><span class="sc">;</span></li><li> <a class="l_k" href="functions/my.html">my</a> <span class="i">$a</span> = <span class="n">1.2</span><span class="sc">;</span></li><li> <a class="l_k" href="functions/print.html">print</a> <a class="l_k" href="functions/eval.html">eval</a> <span class="q">&quot;$a + 1.5&quot;</span><span class="sc">;</span></li><li> <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;\n&quot;</span><span class="sc">;</span></li></ol></pre><p>prints <code class="inline"><span class="n">13</span><span class="cm">,</span><span class="n">5</span></code>
.  This is because in that locale, the comma is the
decimal point character.  The <code class="inline"><a class="l_k" href="functions/eval.html">eval</a></code> thus expands to:</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/eval.html">eval</a> <span class="q">&quot;1,2 + 1.5&quot;</span></li></ol></pre><p>and the result is not what you likely expected.  No warnings are
generated.  If you do string <code class="inline"><a class="l_k" href="functions/eval.html">eval</a></code>'s within the scope of
<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
, you should instead change the <code class="inline"><a class="l_k" href="functions/eval.html">eval</a></code> line to do
something like:</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/print.html">print</a> <a class="l_k" href="functions/eval.html">eval</a> <span class="q">&quot;no locale; $a + 1.5&quot;</span><span class="sc">;</span></li></ol></pre><p>This prints <code class="inline"><span class="n">2.7</span></code>
.</p>
<p>You could also exclude <code class="inline"><span class="w">LC_NUMERIC</span></code>
, if you don't need it, by</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span> <span class="q">&#39;:!numeric&#39;</span><span class="sc">;</span></li></ol></pre><a name="Backward-compatibility"></a><h2>Backward compatibility</h2>
<p>Versions of Perl prior to 5.004 <b>mostly</b> ignored locale information,
generally behaving as if something similar to the <code class="inline"><span class="q">&quot;C&quot;</span></code>
 locale were
always in force, even if the program environment suggested otherwise
(see <a href="#The-setlocale-function">The setlocale function</a>).  By default, Perl still behaves this
way for backward compatibility.  If you want a Perl application to pay
attention to locale information, you <b>must</b> use the <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>

pragma (see <a href="#The-%22use-locale%22-pragma">The use locale pragma</a>) or, in the unlikely event
that you want to do so for just pattern matching, the
<code class="inline"><span class="q">/l</span></code>
 regular expression modifier (see <a href="perlre.html#Character-set-modifiers">Character set modifiers in perlre</a>) to instruct it to do so.</p>
<p>Versions of Perl from 5.002 to 5.003 did use the <code class="inline"><span class="w">LC_CTYPE</span></code>

information if available; that is, <code class="inline">\<span class="w">w</span></code>
 did understand what
were the letters according to the locale environment variables.
The problem was that the user had no control over the feature:
if the C library supported locales, Perl used them.</p>
<a name="I18N%3aCollate-obsolete"></a><h2>I18N:Collate obsolete</h2>
<p>In versions of Perl prior to 5.004, per-locale collation was possible
using the <code class="inline"><span class="w">I18N::Collate</span></code>
 library module.  This module is now mildly
obsolete and should be avoided in new applications.  The <code class="inline"><span class="w">LC_COLLATE</span></code>

functionality is now integrated into the Perl core language: One can
use locale-specific scalar data completely normally with <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
,
so there is no longer any need to juggle with the scalar references of
<code class="inline"><span class="w">I18N::Collate</span></code>
.</p>
<a name="Sort-speed-and-memory-use-impacts"></a><h2>Sort speed and memory use impacts</h2>
<p>Comparing and sorting by locale is usually slower than the default
sorting; slow-downs of two to four times have been observed.  It will
also consume more memory: once a Perl scalar variable has participated
in any string comparison or sorting operation obeying the locale
collation rules, it will take 3-15 times more memory than before.  (The
exact multiplier depends on the string's contents, the operating system
and the locale.) These downsides are dictated more by the operating
system's implementation of the locale system than by Perl.</p>
<a name="Freely-available-locale-definitions"></a><h2>Freely available locale definitions</h2>
<p>The Unicode CLDR project extracts the POSIX portion of many of its
locales, available at</p>
<pre class="verbatim"><ol><li>  <span class="j">http:</span><span class="q">//</span><span class="w">unicode</span>.<span class="w">org</span>/<span class="w">Public</span>/<span class="w">cldr</span><span class="q">/2.0.1/</span></li></ol></pre><p>(Newer versions of CLDR require you to compute the POSIX data yourself.
See <a href="http://unicode.org/Public/cldr/latest/">http://unicode.org/Public/cldr/latest/</a>.)</p>
<p>There is a large collection of locale definitions at:</p>
<pre class="verbatim"><ol><li>  http://std.dkuug.dk/i18n/WG15-collection/locales/</li></ol></pre><p>You should be aware that it is
unsupported, and is not claimed to be fit for any purpose.  If your
system allows installation of arbitrary locales, you may find the
definitions useful as they are, or as a basis for the development of
your own locales.</p>
<a name="I18n-and-l10n"></a><h2>I18n and l10n</h2>
<p>"Internationalization" is often abbreviated as <b>i18n</b> because its first
and last letters are separated by eighteen others.  (You may guess why
the internalin ... internaliti ... i18n tends to get abbreviated.)  In
the same way, "localization" is often abbreviated to <b>l10n</b>.</p>
<a name="An-imperfect-standard"></a><h2>An imperfect standard</h2>
<p>Internationalization, as defined in the C and POSIX standards, can be
criticized as incomplete, ungainly, and having too large a granularity.
(Locales apply to a whole process, when it would arguably be more useful
to have them apply to a single thread, window group, or whatever.)  They
also have a tendency, like standards groups, to divide the world into
nations, when we all know that the world can equally well be divided
into bankers, bikers, gamers, and so on.</p>
<a name="Unicode-and-UTF-8"></a><h1>Unicode and UTF-8</h1>
<p>The support of Unicode is new starting from Perl version v5.6, and more fully
implemented in versions v5.8 and later.  See <a href="perluniintro.html">perluniintro</a>.</p>
<p>Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
<code class="inline"><span class="w">LC_COLLATE</span></code>
 is only partially supported; collation support is improved
in Perl v5.26 to a level that may be sufficient for your needs
(see <a href="#Category-LC_COLLATE-%3a-Collation%3a-Text-Comparisons-and-Sorting">Category LC_COLLATE : Collation: Text Comparisons and Sorting</a>).</p>
<p>If you have Perl v5.16 or v5.18 and can't upgrade, you can use</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span> <span class="q">&#39;:not_characters&#39;</span><span class="sc">;</span></li></ol></pre><p>When this form of the pragma is used, only the non-character portions of
locales are used by Perl, for example <code class="inline"><span class="w">LC_NUMERIC</span></code>
.  Perl assumes that
you have translated all the characters it is to operate on into Unicode
(actually the platform's native character set (ASCII or EBCDIC) plus
Unicode).  For data in files, this can conveniently be done by also
specifying</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/use.html">use</a> <a class="l_k" href="functions/open.html">open</a> <span class="q">&#39;:locale&#39;</span><span class="sc">;</span></li></ol></pre><p>This pragma arranges for all inputs from files to be translated into
Unicode from the current locale as specified in the environment (see
<a href="#ENVIRONMENT">ENVIRONMENT</a>), and all outputs to files to be translated back
into the locale.  (See <a href="open.html">open</a>).  On a per-filehandle basis, you can
instead use the <a href="http://search.cpan.org/perldoc/PerlIO::locale">PerlIO::locale</a> module, or the <a href="http://search.cpan.org/perldoc/Encode::Locale">Encode::Locale</a>
module, both available from CPAN.  The latter module also has methods to
ease the handling of <code class="inline"><span class="w">ARGV</span></code>
 and environment variables, and can be used
on individual strings.  If you know that all your locales will be
UTF-8, as many are these days, you can use the <a href="perlrun.html#-C">-C</a>
command line switch.</p>
<p>This form of the pragma allows essentially seamless handling of locales
with Unicode.  The collation order will be by Unicode code point order.
<a href="Unicode/Collate.html">Unicode::Collate</a> can be used to get Unicode rules collation.</p>
<p>All the modules and switches just described can be used in v5.20 with
just plain <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
, and, should the input locales not be UTF-8,
you'll get the less than ideal behavior, described below, that you get
with pre-v5.16 Perls, or when you use the locale pragma without the
<code class="inline"><span class="j">:</span><span class="w">not_characters</span></code>
 parameter in v5.16 and v5.18.  If you are using
exclusively UTF-8 locales in v5.20 and higher, the rest of this section
does not apply to you.</p>
<p>There are two cases, multi-byte and single-byte locales.  First
multi-byte:</p>
<p>The only multi-byte (or wide character) locale that Perl is ever likely
to support is UTF-8.  This is due to the difficulty of implementation,
the fact that high quality UTF-8 locales are now published for every
area of the world (<a href="http://unicode.org/Public/cldr/2.0.1/">http://unicode.org/Public/cldr/2.0.1/</a> for
ones that are already set-up, but from an earlier version;
<a href="http://unicode.org/Public/cldr/latest/">http://unicode.org/Public/cldr/latest/</a> for the most up-to-date, but
you have to extract the POSIX information yourself), and that
failing all that you can use the <a href="Encode.html">Encode</a> module to translate to/from
your locale.  So, you'll have to do one of those things if you're using
one of these locales, such as Big5 or Shift JIS.  For UTF-8 locales, in
Perls (pre v5.20) that don't have full UTF-8 locale support, they may
work reasonably well (depending on your C library implementation)
simply because both
they and Perl store characters that take up multiple bytes the same way.
However, some, if not most, C library implementations may not process
the characters in the upper half of the Latin-1 range (128 - 255)
properly under <code class="inline"><span class="w">LC_CTYPE</span></code>
.  To see if a character is a particular type
under a locale, Perl uses the functions like <code class="inline"><span class="i">isalnum</span><span class="s">(</span><span class="s">)</span></code>
.  Your C
library may not work for UTF-8 locales with those functions, instead
only working under the newer wide library functions like <code class="inline"><span class="i">iswalnum</span><span class="s">(</span><span class="s">)</span></code>
,
which Perl does not use.
These multi-byte locales are treated like single-byte locales, and will
have the restrictions described below.  Starting in Perl v5.22 a warning
message is raised when Perl detects a multi-byte locale that it doesn't
fully support.</p>
<p>For single-byte locales,
Perl generally takes the tack to use locale rules on code points that can fit
in a single byte, and Unicode rules for those that can't (though this
isn't uniformly applied, see the note at the end of this section).  This
prevents many problems in locales that aren't UTF-8.  Suppose the locale
is ISO8859-7, Greek.  The character at 0xD7 there is a capital Chi. But
in the ISO8859-1 locale, Latin1, it is a multiplication sign.  The POSIX
regular expression character class <code class="inline"><span class="s">[</span><span class="s">[</span><span class="co">:</span><span class="w">alpha</span><span class="co">:</span><span class="s">]</span><span class="s">]</span></code>
 will magically match
0xD7 in the Greek locale but not in the Latin one.</p>
<p>However, there are places where this breaks down.  Certain Perl constructs are
for Unicode only, such as <code class="inline">\<span class="i">p</span><span class="s">{</span><span class="w">Alpha</span><span class="s">}</span></code>
.  They assume that 0xD7 always has its
Unicode meaning (or the equivalent on EBCDIC platforms).  Since Latin1 is a
subset of Unicode and 0xD7 is the multiplication sign in both Latin1 and
Unicode, <code class="inline">\<span class="i">p</span><span class="s">{</span><span class="w">Alpha</span><span class="s">}</span></code>
 will never match it, regardless of locale.  A similar
issue occurs with <code class="inline">\<span class="i">N</span><span class="s">{</span>...<span class="s">}</span></code>
.  Prior to v5.20, It is therefore a bad
idea to use <code class="inline">\<span class="w">p</span><span class="s">{</span><span class="s">}</span></code>
 or
<code class="inline">\<span class="w">N</span><span class="s">{</span><span class="s">}</span></code>
 under plain <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
--<i>unless</i> you can guarantee that the
locale will be ISO8859-1.  Use POSIX character classes instead.</p>
<p>Another problem with this approach is that operations that cross the
single byte/multiple byte boundary are not well-defined, and so are
disallowed.  (This boundary is between the codepoints at 255/256.)
For example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF).  But in the
Greek locale, for example, there is no character at 0xFF, and Perl
has no way of knowing what the character at 0xFF is really supposed to
represent.  Thus it disallows the operation.  In this mode, the
lowercase of U+0178 is itself.</p>
<p>The same problems ensue if you enable automatic UTF-8-ification of your
standard file handles, default <code class="inline"><a class="l_k" href="functions/open.html">open()</a></code> layer, and <code class="inline"><span class="i">@ARGV</span></code>
 on non-ISO8859-1,
non-UTF-8 locales (by using either the <b>-C</b> command line switch or the
<code class="inline"><span class="w">PERL_UNICODE</span></code>
 environment variable; see <a href="perlrun.html">perlrun</a>).
Things are read in as UTF-8, which would normally imply a Unicode
interpretation, but the presence of a locale causes them to be interpreted
in that locale instead.  For example, a 0xD7 code point in the Unicode
input, which should mean the multiplication sign, won't be interpreted by
Perl that way under the Greek locale.  This is not a problem
<i>provided</i> you make certain that all locales will always and only be either
an ISO8859-1, or, if you don't have a deficient C library, a UTF-8 locale.</p>
<p>Still another problem is that this approach can lead to two code
points meaning the same character.  Thus in a Greek locale, both U+03A7
and U+00D7 are GREEK CAPITAL LETTER CHI.</p>
<p>Because of all these problems, starting in v5.22, Perl will raise a
warning if a multi-byte (hence Unicode) code point is used when a
single-byte locale is in effect.  (Although it doesn't check for this if
doing so would unreasonably slow execution down.)</p>
<p>Vendor locales are notoriously buggy, and it is difficult for Perl to test
its locale-handling code because this interacts with code that Perl has no
control over; therefore the locale-handling code in Perl may be buggy as
well.  (However, the Unicode-supplied locales should be better, and
there is a feed back mechanism to correct any problems.  See
<a href="#Freely-available-locale-definitions">Freely available locale definitions</a>.)</p>
<p>If you have Perl v5.16, the problems mentioned above go away if you use
the <code class="inline"><span class="j">:</span><span class="w">not_characters</span></code>
 parameter to the locale pragma (except for vendor
bugs in the non-character portions).  If you don't have v5.16, and you
<i>do</i> have locales that work, using them may be worthwhile for certain
specific purposes, as long as you keep in mind the gotchas already
mentioned.  For example, if the collation for your locales works, it
runs faster under locales than under <a href="Unicode/Collate.html">Unicode::Collate</a>; and you gain
access to such things as the local currency symbol and the names of the
months and days of the week.  (But to hammer home the point, in v5.16,
you get this access without the downsides of locales by using the
<code class="inline"><span class="j">:</span><span class="w">not_characters</span></code>
 form of the pragma.)</p>
<p>Note: The policy of using locale rules for code points that can fit in a
byte, and Unicode rules for those that can't is not uniformly applied.
Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied fairly
consistently to regular expression matching except for bracketed
character classes; in v5.14 it was extended to all regex matches; and in
v5.16 to the casing operations such as <code class="inline">\<span class="w">L</span></code>
 and <code class="inline"><a class="l_k" href="functions/uc.html">uc()</a></code>.  For
collation, in all releases so far, the system's <code class="inline"><span class="i">strxfrm</span><span class="s">(</span><span class="s">)</span></code>
 function is
called, and whatever it does is what you get.  Starting in v5.26, various
bugs are fixed with the way perl uses this function.</p>
<a name="BUGS"></a><h1>BUGS</h1>
<a name="Collation-of-strings-containing-embedded-NUL-characters"></a><h2>Collation of strings containing embedded <code class="inline"><span class="w">NUL</span></code>
 characters</h2>
<p><code class="inline"><span class="w">NUL</span></code>
 characters will sort the same as the lowest collating control
character does, or to <code class="inline"><span class="q">&quot;\001&quot;</span></code>
 in the unlikely event that there are no
control characters at all in the locale.  In cases where the strings
don't contain this non-<code class="inline"><span class="w">NUL</span></code>
 control, the results will be correct, and
in many locales, this control, whatever it might be, will rarely be
encountered.  But there are cases where a <code class="inline"><span class="w">NUL</span></code>
 should sort before this
control, but doesn't.  If two strings do collate identically, the one
containing the <code class="inline"><span class="w">NUL</span></code>
 will sort to earlier.</p>
<a name="Broken-systems"></a><h2>Broken systems</h2>
<p>In certain systems, the operating system's locale support
is broken and cannot be fixed or used by Perl.  Such deficiencies can
and will result in mysterious hangs and/or Perl core dumps when
<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 is in effect.  When confronted with such a system,
please report in excruciating detail to &lt;<i>perlbug@perl.org</i>&gt;, and
also contact your vendor: bug fixes may exist for these problems
in your operating system.  Sometimes such bug fixes are called an
operating system upgrade.  If you have the source for Perl, include in
the perlbug email the output of the test described above in <a href="#Testing-for-broken-locales">Testing for broken locales</a>.</p>
<a name="SEE-ALSO"></a><h1>SEE ALSO</h1>
<p><a href="I18N/Langinfo.html">I18N::Langinfo</a>, <a href="perluniintro.html">perluniintro</a>, <a href="perlunicode.html">perlunicode</a>, <a href="open.html">open</a>,
<a href="POSIX.html#isalnum">isalnum in POSIX</a>, <a href="POSIX.html#isalpha">isalpha in POSIX</a>,
<a href="POSIX.html#isdigit">isdigit in POSIX</a>, <a href="POSIX.html#isgraph">isgraph in POSIX</a>, <a href="POSIX.html#islower">islower in POSIX</a>,
<a href="POSIX.html#isprint">isprint in POSIX</a>, <a href="POSIX.html#ispunct">ispunct in POSIX</a>, <a href="POSIX.html#isspace">isspace in POSIX</a>,
<a href="POSIX.html#isupper">isupper in POSIX</a>, <a href="POSIX.html#isxdigit">isxdigit in POSIX</a>, <a href="POSIX.html#localeconv">localeconv in POSIX</a>,
<a href="POSIX.html#setlocale">setlocale in POSIX</a>, <a href="POSIX.html#strcoll">strcoll in POSIX</a>, <a href="POSIX.html#strftime">strftime in POSIX</a>,
<a href="POSIX.html#strtod">strtod in POSIX</a>, <a href="POSIX.html#strxfrm">strxfrm in POSIX</a>.</p>
<p>For special considerations when Perl is embedded in a C program,
see <a href="perlembed.html#Using-embedded-Perl-with-POSIX-locales">Using embedded Perl with POSIX locales in perlembed</a>.</p>
<a name="HISTORY"></a><h1>HISTORY</h1>
<p>Jarkko Hietaniemi's original <i>perli18n.pod</i> heavily hacked by Dominic
Dunlop, assisted by the perl5-porters.  Prose worked over a bit by
Tom Christiansen, and updated by Perl 5 porters.</p>




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      <ul><li><a href="#NAME">NAME</a><li><a href="#DESCRIPTION">DESCRIPTION</a><li><a href="#WHAT-IS-A-LOCALE">WHAT IS A LOCALE</a><li><a href="#PREPARING-TO-USE-LOCALES">PREPARING TO USE LOCALES</a><li><a href="#USING-LOCALES">USING LOCALES</a><ul><li><a href="#The-%22use-locale%22-pragma">The "use locale" pragma</a><li><a href="#The-setlocale-function">The setlocale function</a><li><a href="#Finding-locales">Finding locales</a><li><a href="#LOCALE-PROBLEMS">LOCALE PROBLEMS</a><li><a href="#Testing-for-broken-locales">Testing for broken locales</a><li><a href="#Temporarily-fixing-locale-problems">Temporarily fixing locale problems</a><li><a href="#Permanently-fixing-locale-problems">Permanently fixing locale problems</a><li><a href="#Permanently-fixing-your-system's-locale-configuration">Permanently fixing your system's locale configuration</a><li><a href="#Fixing-system-locale-configuration">Fixing system locale configuration</a><li><a href="#The-localeconv-function">The localeconv function</a><li><a href="#I18N%3a%3aLanginfo">I18N::Langinfo</a></ul><li><a href="#LOCALE-CATEGORIES">LOCALE CATEGORIES</a><ul><li><a href="#Category-LC_COLLATE%3a-Collation%3a-Text-Comparisons-and-Sorting">Category LC_COLLATE: Collation: Text Comparisons and Sorting</a><li><a href="#Category-LC_CTYPE%3a-Character-Types">Category LC_CTYPE: Character Types</a><li><a href="#Category-LC_NUMERIC%3a-Numeric-Formatting">Category LC_NUMERIC: Numeric Formatting</a><li><a href="#Category-LC_MONETARY%3a-Formatting-of-monetary-amounts">Category LC_MONETARY: Formatting of monetary amounts</a><li><a href="#Category-LC_TIME%3a-Respresentation-of-time">Category LC_TIME: Respresentation of time</a><li><a href="#Other-categories">Other categories</a></ul><li><a href="#SECURITY">SECURITY</a><li><a href="#ENVIRONMENT">ENVIRONMENT</a><ul><li><a href="#Examples">Examples</a></ul><li><a href="#NOTES">NOTES</a><ul><li><a href="#String-eval-and-LC_NUMERIC">String eval and LC_NUMERIC</a><li><a href="#Backward-compatibility">Backward compatibility</a><li><a href="#I18N%3aCollate-obsolete">I18N:Collate obsolete</a><li><a href="#Sort-speed-and-memory-use-impacts">Sort speed and memory use impacts</a><li><a href="#Freely-available-locale-definitions">Freely available locale definitions</a><li><a href="#I18n-and-l10n">I18n and l10n</a><li><a href="#An-imperfect-standard">An imperfect standard</a></ul><li><a href="#Unicode-and-UTF-8">Unicode and UTF-8</a><li><a href="#BUGS">BUGS</a><ul><li><a href="#Collation-of-strings-containing-embedded-NUL-characters">Collation of strings containing embedded NUL characters</a><li><a href="#Broken-systems">Broken systems</a></ul><li><a href="#SEE-ALSO">SEE ALSO</a><li><a href="#HISTORY">HISTORY</a></ul>
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