newlib/winsup/doc/setup2.sgml

<sect1 id="setup-env"><title>Environment Variables</title>

<para>
You may wish to specify settings of several important environment
variables that affect Cygwin's operation.  Some of these settings need
to be in effect prior to launching the initial Cygwin session (before
starting your bash shell, for instance), and are, consequentially, best
placed in a .bat file.  An initial file is named Cygwin.bat and is created
in the Cygwin root directory that you specified during setup.  Note that
the "Cygwin" option of the Start Menu points to Cygwin.bat.  Edit
Cygwin.bat to your liking or create your own .bat files to start
Cygwin processes.</para>

<para>
The <envar>CYGWIN</envar> variable is used to configure many global
settings for the Cygwin runtime system.  Initially you can leave
<envar>CYGWIN</envar> unset or set it to <literal>tty</literal> (e.g.
to support job control with ^Z etc...) using a syntax like this in the
DOS shell, before launching bash.</para>

<screen>
<prompt>C:\&gt;</prompt> <userinput>set CYGWIN=tty notitle glob</userinput>
</screen>

<para>
Locale support is controlled by the <envar>LANG</envar> and
<envar>LC_xxx</envar> environment variables.  You can set all of them
but Cygwin itself only honors the variables <envar>LC_ALL</envar>,
<envar>LC_CTYPE</envar>, and <envar>LANG</envar>, in this order, according
to the POSIX standard.  The first one found rules.  For a more detailed
description see <xref linkend="setup-locale"></xref>.
</para>

<para>
The <envar>PATH</envar> environment variable is used by Cygwin
applications as a list of directories to search for executable files
to run.  This environment variable is converted from Windows format
(e.g. <filename>C:\Windows\system32;C:\Windows</filename>) to UNIX format
(e.g., <filename>/cygdrive/c/Windows/system32:/cygdrive/c/Windows</filename>)
when a Cygwin process first starts.
Set it so that it contains at least the <filename>x:\cygwin\bin</filename>
directory where "<filename>x:\cygwin</filename> is the "root" of your
cygwin installation if you wish to use cygwin tools outside of bash.
This is usually done by the batch file you're starting your shell with.
</para>

<para> 
The <envar>HOME</envar> environment variable is used by many programs to
determine the location of your home directory and we recommend that it be
defined.  This environment variable is also converted from Windows format
when a Cygwin process first starts.  It's usually set in the shell
profile scripts in the /etc directory.
</para>

<para>
The <envar>TERM</envar> environment variable specifies your terminal
type.  It is automatically set to <literal>cygwin</literal> if you have
not set it to something else.
</para>

<para>The <envar>LD_LIBRARY_PATH</envar> environment variable is used by
the Cygwin function <function>dlopen ()</function> as a list of
directories to search for .dll files to load.  This environment variable
is converted from Windows format to UNIX format when a Cygwin process
first starts.  Most Cygwin applications do not make use of the
<function>dlopen ()</function> call and do not need this variable.
</para>

</sect1>

<sect1 id="setup-maxmem"><title>Changing Cygwin's Maximum Memory</title>

<para>
Cygwin's heap is extensible.  However, it does start out at a fixed size
and attempts to extend it may run into memory which has been previously
allocated by Windows.  In some cases, this problem can be solved by
adding an entry in the either the <literal>HKEY_LOCAL_MACHINE</literal>
(to change the limit for all users) or
<literal>HKEY_CURRENT_USER</literal> (for just the current user) section
of the registry.  </para>

<para>
Add the <literal>DWORD</literal> value <literal>heap_chunk_in_mb</literal> 
and set it to the desired memory limit in decimal MB. It is preferred to do 
this in Cygwin using the <command>regtool</command> program included in the 
Cygwin package.
(For more information about <command>regtool</command> or the other Cygwin 
utilities, see <xref linkend="using-utils"></xref> or use the
<literal>--help</literal> option of each util.)  You should always be careful 
when using <command>regtool</command> since damaging your system registry can 
result in an unusable system.  This example sets memory limit to 1024 MB:

<screen>
regtool -i set /HKLM/Software/Cygwin/heap_chunk_in_mb 1024
regtool -v list /HKLM/Software/Cygwin
</screen>
</para>

<para>
Exit all running Cygwin processes and restart them. Memory can be allocated up 
to the size of the system swap space minus any the size of any running 
processes. The system swap should be at least as large as the physically 
installed RAM and can be modified under the System category of the 
Control Panel.  
</para>

<para>
Here is a small program written by DJ Delorie that tests the 
memory allocation limit on your system:

<screen>
main()
{
  unsigned int bit=0x40000000, sum=0;
  char *x;
  
  while (bit > 4096) 
  {
    x = malloc(bit);
    if (x)
    sum += bit;
    bit >>= 1;
  }
  printf("%08x bytes (%.1fMb)\n", sum, sum/1024.0/1024.0);
  return 0;
}
</screen>

You can compile this program using:
<screen>
gcc max_memory.c -o max_memory.exe
</screen>

Run the program and it will output the maximum amount of allocatable memory.
</para>

</sect1>

<sect1 id="setup-locale"><title>Internationalization</title>

<sect2 id="setup-locale-ov"><title>Overview</title>

<para>
Internationalization support is controlled by the <envar>LANG</envar> and
<envar>LC_xxx</envar> environment variables.  You can set all of them
but Cygwin itself only honors the variables <envar>LC_ALL</envar>,
<envar>LC_CTYPE</envar>, and <envar>LANG</envar>, in this order, according
to the POSIX standard.  The content of these variables should follow the
POSIX standard for a locale specifier.  The correct form of a locale
specifier is</para>

<screen>
  language[[_TERRITORY][.charset][@modifier]]
</screen>

<para>"language" is a lowercase two character string per ISO 639-1,
"TERRITORY" is an uppercase two character string per ISO 3166, charset is
one of a list of supported character sets, and the modifier doesn't matter
here (though it might for some applications).  If you're interested in the
exact description, you can find it in the online publication of the POSIX
manual pages on the homepage of the
<ulink url="http://www.opengroup.org/">Open Group</ulink>.</para>

<para>Typical locale specifiers are</para>

<screen>
  "de_CH"	   language = German, territory = Switzerland, default charset
  "fr_FR.UTF-8"    language = french, territory = France, charset = UTF-8
  "ko_KR.eucKR"    language = korean, territory = South Korea, charset = eucKR
</screen>

<para>
And let's not forget the default locale called "C" or "POSIX"
which basically only supports plain ASCII code.  If the aforementioned
environment variables are not set, or set to "C" or "POSIX", you get the
default ASCII-only behaviour.
</para>

<para>
Right now the language and territory, as well as the modifier, are not
important to Cygwin, except to fix a single problem.  There's a class of
characters in the Unicode character set, called the "CJK Ambiguous Width
Character set".  For these characters the width returned by the
wcwidth/wcswidth function is usually 1.  This is often a problem in
East-Asian languages, which historically use character sets in which
these characters have a width of 2.  Kind of explains why they are
called "ambiguous"...</para>

<para>
The problem has been fixed for now like this.  wcwidth/wcswidth usually
return 1 as the width of these characters.  However, if the language is
specifed as "ja" (Japanese), "ko" (Korean), or "zh" (Chinese), wcwidth
returns 2 for these characters.  Unfortunately this isn't correct in
all circumstances, so the user can specify the modifier "@cjknarrow",
which modifies the behaviour of wcwidth/wcswidth to return 1 for the
ambiguous width characters to return 1 even in those languages.</para>

<para>
Other than that, the only important part so far is the character set.
How does that work?</para>

</sect2>

<sect2 id="setup-locale-how"><title>How to set the locale</title>

<itemizedlist mark="bullet">

<listitem><para>
The default locale is the "C" or "POSIX" locale.  In this locale, basically
only ASCII characters are supported.  Even if one of the aforementioned
environment variables are set to something else, it's the application's
responsibility to call the function <function>setlocale</function>,
typically like this</para>

<screen>
  setlocale (LC_ALL, "");
</screen>

<para>to switch to another locale according to the settings of the
internationalization environment variables.
</para></listitem>

<listitem><para>
Assume that you've set one of the aforementioned environment variables to some
valid POSIX locale value, other than "C" and "POSIX", and assume that you
call an application which calls <function>setlocale</function> as above.</para>

<para>Assume further that you're living in Japan.  You might want to use
the language code "ja" and the territory "JP", thus setting, say,
<envar>LANG</envar> to "ja_JP".  You didn't set a character set, so
what will Cygwin use now?  Easy!  It will use the default Windows ANSI
codepage of your system, if it's supported by Cygwin.  Hopefully Cygwin
supports all relevant default ANSI codepages...</para>

<note><para>For a list of supported character sets, see
<xref linkend="setup-locale-charsetlist"></xref>
</para></note>
</listitem>

<listitem><para>
You don't want to use the default Windows codepage as character set?
In that case you have to specify the charset explicitly.  For instance,
assume you're from Italy and don't want to use the default Windows codepage
1252, but the more portable ISO-8859-15 character set.  What you can do is
to set the <envar>LANG</envar> variable in the
<filename>C:\cygwin\Cygwin.bat</filename> file which is the batch file
to start a Cygwin session from the "Cygwin" desktop shortcut.</para>

<screen>
  @echo off

  C:
  chdir C:\cygwin\bin
  set LANG=it_IT.ISO-8859-15
  bash --login -i
</screen>
</listitem>

<listitem><para>
Most singlebyte or doublebyte charsets have a disadvantage.  Windows
filesystems use the Unicode character set in the UTF-16 encoding to store filename information.  Not all characters
from the Unicode character set are available in a singlebyte or doublebyte
charset.  While Cygwin has a workaround to access files with unusual
characters (see <xref linkend="pathnames-unusual"></xref>), a better
workaround is to use always the UTF-8 character set.  UTF-8 is the only
multibyte character set which can represent <emphasis>every</emphasis>
Unicode character.</para>

<screen>
  set LANG=es_MX.UTF-8
</screen>

<para>For a description of the Unicode standard, see the homepage of the
<ulink url="http://www.unicode.org/">Unicode Consortium</ulink>.
</para></listitem>

</itemizedlist>

</sect2>

<!-- TODO: This is not correct anymore.
<sect2 id="setup-locale-console"><title>The Windows Console character set</title>

<para>Most of the time the Windows console is used to run Cygwin applications.
While terminal emulations like <command>xterm</command> or
<command>mintty</command> have a distinct way to set the character set
used for in- and output, the Windows console hasn't such a way, since it's
not an application in its own right.</para>

<para>This problem is solved in Cygwin as follows.  When the first Cygwin
process is started in a Windows console (either explicitly from cmd.exe,
or implicitly by, for instance, clicking on the Cygwin desktop icon, or
running the Cygwin.bat file), the Console character set is determined by the
setting of the aforementioned internationalization environment variables,
the same way as described in <xref linkend="setup-locale-how"></xref>.
</para>

<para>However, in contrast to the application's character set, which is
determined by the <function>setlocale</function> call, the console
character set stays fixed for all subsequent Cygwin processes started
from this first Cygwin process in the console.  So, for instance, if
<envar>LANG</envar> was set to "en_US.UTF-8" when the first Cygwin process
started, the console is a UTF-8 terminal for the entire Cygwin process
tree started from this first Cygwin process.</para>

<para>You're asking "What is that good for?  Why not switch the console
character set with the applications requirements?  After all, the
application knows if it uses localization or not."  That's true, but
what if the non-localized application calls a remote application which
itself is localized?  This can happen with <command>ssh</command> or
<command>rlogin</command>.  Both commands don't have and don't need
localization and they never call <function>setlocale</function>.  This
would have the unfortunate effect, that the console would run with the
ASCII character set alone.  Native characters printed from the remote
application would not show up correctly on your local console.</para>

</sect2>
-->

<sect2 id="setup-locale-problems"><title>Potential Problems when using Locales</title>

<para>
You can set the above internationalization variables not only in
<filename>Cygwin.bat</filename> or in the Windows environment, but also
in your Cygwin shell on the fly, even switch to yet another character
set, and yet another.  In bash for instance:</para>

<screen>
  <prompt>bash$</prompt> export LC_CTYPE="nl_BE.UTF-8"
</screen>

<para>However, here's a problem.  At the start of the first Cygwin process
in a session, the Windows environment has to be converted from UTF-16 to
some singlebyte or multibyte charset.  If the internationalization environment
variable hasn't been set <emphasis>before</emphasis> starting this process,
Cygwin has to make an educated guess which charset to use to convert
the environment itself.  The only reproducible way to do that in the absence
of <envar>LC_ALL</envar>, <envar>LC_CTYPE</envar>, or <envar>LANG</envar>,
is to use the "C" locale.  The default conversion in the "C" locale
used by Cygwin internally is UTF-8.  So, in the absence of any
internationalization environment variable, the environment will be converted
to UTF-8.</para>

<para>As long as the environment only contains ASCII characters, this is
no problem at all.  But if it contains native characters, and you're planning
to use, say, GBK, the environment will result in invalid characters in
the GBK charset.  This would be especially a problem in variables like
<envar>PATH</envar>.</para>

<note><para>Per POSIX, the name of an environment variable should only
consist of valid ASCII characters, and only of uppercase letters, digits, and
the underscore for maximum portablilty.</para></note>

<para>Symbolic links, too, may pose a problem when switching charsets on
the fly.  A symbolic link contains the filename of the target file the
symlink points to.  When a symlink had been created with older versions
of Cygwin, the current ANSI or OEM character set had been used to store
the target filename, dependent on the old <envar>CYGWIN</envar>
environment variable setting <envar>codepage</envar> (see <xref
linkend="cygwinenv-removed-options"></xref>.  If the target filename
contains non-ASCII characters and you use another character set than
your default ANSI/OEM charset, the target filename of the symlink is now
potentially an invalid character sequence in the new character set.
This behaviour is not different from the behaviour in other Operating
Systems.  So, if you suddenly can't access a symlink anymore which
worked all these years before, maybe it's because you switched to
another character set.  This doesn't occur with symlinks created with
Cygwin 1.7 or later.  </para>

</sect2>

<sect2 id="setup-locale-missing"><title>What does not work?</title>

<para>
Except for <envar>LC_ALL</envar>, <envar>LC_CTYPE</envar>,
and <envar>LANG</envar>, all other LC_xxx environment variables,
<envar>LC_COLLATE</envar>, <envar>LC_MESSAGES</envar>,
<envar>LC_MONETARY</envar>, <envar>LC_NUMERIC</envar>,
and <envar>LC_TIME</envar>, are ignored right now.  This means, while Cygwin
supports different character sets, it does <emphasis>not</emphasis> support
real localization so far.  There's no support for locale-specific monetary
symbols, for a decimalpoint other than '.', no support for native time
formats, and no support for native language sorting orders.
</para>

<para>Cygwin's internationalization support is work in progress and we would
be glad for coding help in this area.</para>

</sect2>

<sect2 id="setup-locale-charsetlist"><title>List of supported character sets</title>

<para>Last but not least, here's the list of currently supported character
sets.  The left-hand expression is the name of the charset, as you would use
it in the internationalization environment variables as outlined above.
</para>

<para>The right-hand side is the number of the equivalent Windows
codepage as well as the Windows name of the codepage.  They are only
noted here for reference.  Don't try to use the bare codepage number or
the Windows name of the codepage as charset in locale specifiers, unless
they happen to be identical with the left-hand side.  Especially in case
oif the "CPxxx" style charsets, always use them with the trailing "CP".</para>

<para>This works:</para>

<screen>
  set LC_ALL=en_US.CP437
</screen>

<para>This does <emphasis>not</emphasis> work:</para>

<screen>
  set LC_ALL=en_US.437
</screen>

<para>You can find a full list of Windows codepages on the Microsoft MSDN page
<ulink url="http://msdn.microsoft.com/en-us/library/dd317756(VS.85).aspx">Code Page Identifiers</ulink>.</para>

<screen>
    Charset               Codepage

    CP437                   437 (OEM United States)
    CP720                   720 (DOS Arabic)
    CP737                   737 (OEM Greek)
    CP775                   775 (OEM Baltic)
    CP850                   850 (OEM Latin 1, Western European)
    CP852                   852 (OEM Latin 2, Central European)
    CP855                   855 (OEM Cyrillic)
    CP857                   857 (OEM Turkish)
    CP858                   858 (OEM Latin 1 + Euro Symbol)
    CP862                   862 (OEM Hebrew)
    CP866                   866 (OEM Russian)
    CP874                   874 (ANSI/OEM Thai)
    CP1125                 1125 (OEM Ukraine)
    CP1250                 1250 (ANSI Central European)
    CP1251                 1251 (ANSI Cyrillic)
    CP1252                 1252 (ANSI Latin 1, Western European)
    CP1253                 1253 (ANSI Greek)
    CP1254                 1254 (ANSI Turkish)
    CP1255                 1255 (ANSI Hebrew)
    CP1256                 1256 (ANSI Arabic)
    CP1257                 1257 (ANSI Baltic)
    CP1258                 1258 (ANSI/OEM Vietnamese)

    ISO-8859-1            28591 (ISO-8859-1)
    ISO-8859-2            28592 (ISO-8859-2)
    ISO-8859-3            28593 (ISO-8859-3)
    ISO-8859-4            28594 (ISO-8859-4)
    ISO-8859-5            28595 (ISO-8859-5)
    ISO-8859-6            28596 (ISO-8859-6)
    ISO-8859-7            28597 (ISO-8859-7)
    ISO-8859-8            28598 (ISO-8859-8)
    ISO-8859-9            28599 (ISO-8859-9)
    ISO-8859-10             -   (not available)
    ISO-8859-11             -   (not available)
    ISO-8859-13           28603 (ISO-8859-13)
    ISO-8859-14             -   (not available)
    ISO-8859-15           28605 (ISO-8859-15)
    ISO-8859-16             -   (not available)

    SJIS                    932 (ANSI/OEM Japanese)
    GBK                     936 (ANSI/OEM Simplified Chinese)
    Big5                    950 (ANSI/OEM Traditional Chinese)
    eucJP                 20932 (EUC Japanese)
    eucKR                   949 (EUC Korean)

    UTF-8                 65001 (UTF-8)
</screen>

</sect2>

</sect1>

<sect1 id="setup-files"><title>Customizing bash</title>

<para>
To set up bash so that cut and paste work properly, click on the
"Properties" button of the window, then on the "Misc" tab.  Make sure
that "QuickEdit mode" and "Insert mode" are checked.  These settings
will be remembered next time you run bash from that shortcut. Similarly
you can set the working directory inside the "Program" tab. The entry
"%HOME%" is valid, but requires that you set <envar>HOME</envar> in
the Windows environment.
</para>

<para>
Your home directory should contain three initialization files
that control the behavior of bash.  They are
<filename>.profile</filename>, <filename>.bashrc</filename> and
<filename>.inputrc</filename>.  The Cygwin base installation creates
stub files when you start bash for the first time.</para>

<para>
<filename>.profile</filename> (other names are also valid, see the bash man
page) contains bash commands.  It is executed when bash is started as login
shell, e.g. from the command <command>bash --login</command>.
This is a useful place to define and
export environment variables and bash functions that will be used by bash
and the programs invoked by bash.  It is a good place to redefine
<envar>PATH</envar> if needed.  We recommend adding a ":." to the end of
<envar>PATH</envar> to also search the current working directory (contrary
to DOS, the local directory is not searched by default).  Also to avoid
delays you should either <command>unset</command> <envar>MAILCHECK</envar> 
or define <envar>MAILPATH</envar> to point to your existing mail inbox.
</para>

<para>
<filename>.bashrc</filename> is similar to
<filename>.profile</filename> but is executed each time an interactive
bash shell is launched.  It serves to define elements that are not
inherited through the environment, such as aliases. If you do not use
login shells, you may want to put the contents of
<filename>.profile</filename> as discussed above in this file
instead.
</para>

<para>
<screen>
shopt -s nocaseglob
</screen>
will allow bash to glob filenames in a case-insensitive manner.
Note that <filename>.bashrc</filename> is not called automatically for login 
shells. You can source it from <filename>.profile</filename>.
</para>

<para>
<filename>.inputrc</filename> controls how programs using the readline
library (including <command>bash</command>) behave.  It is loaded
automatically.  For full details see the <literal>Function and Variable
Index</literal> section of the GNU <systemitem>readline</systemitem> manual.
Consider the following settings:
<screen>
# Ignore case while completing
set completion-ignore-case on
# Make Bash 8bit clean
set meta-flag on
set convert-meta off
set output-meta on
</screen>
The first command makes filename completion case insensitive, which can
be convenient in a Windows environment.  The next three commands allow
<command>bash</command> to display 8-bit characters, useful for
languages with accented characters.  Note that tools that do not use
<systemitem>readline</systemitem> for display, such as
<command>less</command> and <command>ls</command>, require additional
settings, which could be put in your <filename>.bashrc</filename>:
<screen>
alias less='/bin/less -r'
alias ls='/bin/ls -F --color=tty --show-control-chars'
</screen>
</para>

</sect1>