lfs-book/chapter07/locale.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
]>

<sect1 id="ch-scripts-locale">
  <?dbhtml filename="locale.html"?>

  <title>Configuring the System Locale</title>

  <indexterm zone="ch-scripts-locale">
    <primary sortas="e-etc-locale-conf">/etc/locale.conf</primary>
  </indexterm>

  <para>The <filename>/etc/locale.conf</filename> below sets some
  environment variables necessary for native language support. Setting
  them properly results in:</para>

  <itemizedlist>
    <listitem>
      <para>The output of programs translated into the native language</para>
    </listitem>
    <listitem>
      <para>Correct classification of characters into letters, digits and other
      classes. This is necessary for <command>bash</command> to properly accept
      non-ASCII characters in command lines in non-English locales</para>
    </listitem>
    <listitem>
      <para>The correct alphabetical sorting order for the country</para>
    </listitem>
    <listitem>
      <para>Appropriate default paper size</para>
    </listitem>
    <listitem>
      <para>Correct formatting of monetary, time, and date values</para>
    </listitem>
  </itemizedlist>

  <para>Replace <replaceable>&lt;ll&gt;</replaceable> below with the two-letter code
  for the desired language (e.g., <quote>en</quote>) and
  <replaceable>&lt;CC&gt;</replaceable> with the two-letter code for the appropriate
  country (e.g., <quote>GB</quote>). <replaceable>&lt;charmap&gt;</replaceable> should
  be replaced with the canonical charmap for your chosen locale. Optional
  modifiers such as <quote>@euro</quote> may also be present.</para>

  <para>The list of all locales supported by Glibc can be obtained by running
  the following command:</para>

<screen role="nodump"><userinput>locale -a</userinput></screen>

  <para>Charmaps can have a number of aliases, e.g., <quote>ISO-8859-1</quote>
  is also referred to as <quote>iso8859-1</quote> and <quote>iso88591</quote>.
  Some applications cannot handle the various synonyms correctly (e.g., require
  that <quote>UTF-8</quote> is written as <quote>UTF-8</quote>, not
  <quote>utf8</quote>), so it is safest in most
  cases to choose the canonical name for a particular locale. To determine
  the canonical name, run the following command, where <replaceable>&lt;locale
  name&gt;</replaceable> is the output given by <command>locale -a</command> for
  your preferred locale (<quote>en_GB.iso88591</quote> in our example).</para>

<screen role="nodump"><userinput>LC_ALL=<replaceable>&lt;locale name&gt;</replaceable> locale charmap</userinput></screen>

  <para>For the <quote>en_GB.iso88591</quote> locale, the above command
  will print:</para>

<screen><computeroutput>ISO-8859-1</computeroutput></screen>

  <para>This results in a final locale setting of <quote>en_GB.ISO-8859-1</quote>.
  It is important that the locale found using the heuristic above is tested prior
  to it being added to the Bash startup files:</para>

<screen role="nodump"><userinput>LC_ALL=&lt;locale name&gt; locale language
LC_ALL=&lt;locale name&gt; locale charmap
LC_ALL=&lt;locale name&gt; locale int_curr_symbol
LC_ALL=&lt;locale name&gt; locale int_prefix</userinput></screen>

  <para>The above commands should print the language name, the character
  encoding used by the locale, the local currency, and the prefix to dial
  before the telephone number in order to get into the country. If any of the
  commands above fail with a message similar to the one shown below, this means
  that your locale was either not installed in Chapter 6 or is not supported by
  the default installation of Glibc.</para>

<screen><computeroutput>locale: Cannot set LC_* to default locale: No such file or directory</computeroutput></screen>

  <para>If this happens, you should either install the desired locale using the
  <command>localedef</command> command, or consider choosing a different locale.
  Further instructions assume that there are no such error messages from
  Glibc.</para>

  <!-- FIXME: the xlib example will became obsolete real soon -->
  <para>Some packages beyond LFS may also lack support for your chosen locale. One
  example is the X library (part of the X Window System), which outputs the
  following error message if the locale does not exactly match one of the character
  map names in its internal files:</para>

<screen><computeroutput>Warning: locale not supported by Xlib, locale set to C</computeroutput></screen>

  <para>In several cases Xlib expects that the character map will be listed in
  uppercase notation with canonical dashes. For instance, "ISO-8859-1" rather
  than "iso88591". It is also  possible to find an appropriate specification by
  removing the charmap part of the locale specification.  This can be checked
  by running the <command>locale charmap</command> command in both locales.
  For example, one would have to change "de_DE.ISO-8859-15@euro" to
  "de_DE@euro" in order to get this locale recognized by Xlib.</para>

  <para>Other packages can also function incorrectly (but may not necessarily
  display any error messages) if the locale name does not meet their expectations.
  In those cases, investigating how other Linux distributions support your locale
  might provide some useful information.</para>

  <para>Once the proper locale settings have been determined, create the
  <filename>/etc/locale.conf</filename> file:</para>

<screen><userinput>cat &gt; /etc/locale.conf &lt;&lt; "EOF"
<literal>LANG=<replaceable>&lt;ll&gt;_&lt;CC&gt;.&lt;charmap&gt;&lt;@modifiers&gt;</replaceable></literal>
EOF</userinput></screen>

  <para>Note that you can modify <filename>/etc/locale.conf</filename> with
  Systemd <command>localectl</command> utility. To use <command>localectl</command>
  for the example above, run:</para>

<screen role="nodump"><userinput>localectl set-locale LANG="<replaceable>&lt;ll&gt;_&lt;CC&gt;.&lt;charmap&gt;&lt;@modifiers&gt;</replaceable>"</userinput></screen>

  <para>You can also specify other language specific environment variables such
  as <envar>LANG</envar>, <envar>LC_CTYPE</envar>, <envar>LC_NUMERIC</envar> or
  any other environment variable from <command>locale</command> output. Just
  seperate them with a space. An example where <envar>LANG</envar> is set as
  en_US.UTF-8 but <envar>LC_CTYPE</envar> is set as just en_US is:</para>

<screen role="nodump"><userinput>localectl set-locale LANG="en_US.UTF-8" LC_CTYPE="en_US"</userinput></screen>

  <note><para>Please note that <command>localectl</command> command can
  be used  only on a system booted with Systemd.</para></note>

  <para>The <quote>C</quote> (default) and <quote>en_US</quote> (the recommended
  one for United States English users) locales are different. <quote>C</quote>
  uses the US-ASCII 7-bit character set, and treats bytes with the high bit set
  as invalid characters. That's why, e.g., the <command>ls</command> command
  substitutes them with question marks in that locale. Also, an attempt to send
  mail with such characters from Mutt or Pine results in non-RFC-conforming
  messages being sent (the charset in the outgoing mail is indicated as <quote>unknown
  8-bit</quote>). So you can use the <quote>C</quote> locale only if you are sure that
  you will never need 8-bit characters.</para>

  <para>UTF-8 based locales are not supported well by many programs.
  Work is in progress to document and, if possible, fix such problems, see
  <ulink url="&blfs-root;view/svn/introduction/locale-issues.html"/>.</para>

</sect1>