137 lines
5.2 KiB
XML
137 lines
5.2 KiB
XML
<?xml version="1.0" encoding='UTF-8'?>
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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<sect1 id="setup-env"><title>Environment Variables</title>
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<sect2 id="setup-env-ov"><title>Overview</title>
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<para>
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All Windows environment variables are imported when Cygwin starts.
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Apart from that, you may wish to specify settings of several important
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environment variables that affect Cygwin's operation.</para>
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<para>
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The <envar>CYGWIN</envar> variable is used to configure a few global
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settings for the Cygwin runtime system. Typically you can leave
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<envar>CYGWIN</envar> unset, but if you want to set one ore more
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options, you can set it using a syntax like this, depending on the shell
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in which you're setting it. Here is an example in CMD syntax:</para>
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<screen>
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<prompt>C:\></prompt> <userinput>set CYGWIN=error_start:C:\cygwin\bin\gdb.exe glob</userinput>
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</screen>
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<para>
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This is, of course, just an example. For the recognized settings of the
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<envar>CYGWIN</envar> environment variable, see
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<xref linkend="using-cygwinenv"></xref>.
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</para>
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<para>
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Locale support is controlled by the <envar>LANG</envar> and
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<envar>LC_xxx</envar> environment variables. For a more detailed description
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see <xref linkend="setup-locale"></xref>.
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</para>
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<para>
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The <envar>PATH</envar> environment variable is used by Cygwin
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applications as a list of directories to search for executable files
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to run. This environment variable is converted from Windows format
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(e.g. <filename>C:\Windows\system32;C:\Windows</filename>) to UNIX format
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(e.g., <filename>/cygdrive/c/Windows/system32:/cygdrive/c/Windows</filename>)
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when a Cygwin process first starts.
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Set it so that it contains at least the <filename>x:\cygwin\bin</filename>
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directory where "<filename>x:\cygwin</filename> is the "root" of your
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cygwin installation if you wish to use cygwin tools outside of bash.
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This is usually done by the batch file you're starting your shell with.
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</para>
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<para>
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The <envar>HOME</envar> environment variable is used by many programs to
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determine the location of your home directory. This environment variable,
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if it exists, is converted from Windows format when a Cygwin process first
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starts. However, it's usually set in the shell profile scripts in the /etc
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directory, and it's <emphasis role='bold'>not</emphasis> recommended to set
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the variable in your Windows environment.
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</para>
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<para>
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The <envar>TERM</envar> environment variable specifies your terminal
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type. It is automatically set to <literal>cygwin</literal> if you have
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not set it to something else.
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</para>
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<para>The <envar>LD_LIBRARY_PATH</envar> environment variable is used by
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the Cygwin function <function>dlopen ()</function> as a list of
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directories to search for .dll files to load. This environment variable
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is converted from Windows format to UNIX format when a Cygwin process
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first starts. Most Cygwin applications do not make use of the
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<function>dlopen ()</function> call and do not need this variable.
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</para>
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<para>The <envar>GMON_OUT_PREFIX</envar> environment variable is helpful
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in some situations when profiling Cygwin programs. For more information,
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see <xref linkend="gprof-fork"></xref>. Only software developers with a
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need to profile their programs have a use for this variable.
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</para>
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<para>
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In addition to <envar>PATH</envar>, <envar>HOME</envar>,
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<envar>LD_LIBRARY_PATH</envar>, and <envar>GMON_OUT_PREFIX</envar>,
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there are three other environment
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variables which, if they exist in the Windows environment, are
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converted to UNIX format: <envar>TMPDIR</envar>, <envar>TMP</envar>,
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and <envar>TEMP</envar>. The first is not set by default in the
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Windows environment but the other two are, and they point to the
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default Windows temporary directory. If set, these variables will be
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used by some Cygwin applications, possibly with unexpected results.
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You may therefore want to unset them by adding the following two lines
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to your <filename>~/.bashrc</filename> file:
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<screen>
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unset TMP
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unset TEMP
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</screen>
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This is done in the default <filename>~/.bashrc</filename> file.
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Alternatively, you could set <envar>TMP</envar>
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and <envar>TEMP</envar> to point to <filename>/tmp</filename> or to
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any other temporary directory of your choice. For example:
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<screen>
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export TMP=/tmp
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export TEMP=/tmp
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</screen>
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</para>
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</sect2>
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<sect2 id="setup-env-win32"><title>Restricted Win32 environment</title>
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<para>There is a restriction when calling Win32 API functions which
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require a fully set up application environment. Cygwin maintains its own
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environment in POSIX style. The Win32 environment is usually stripped
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to a bare minimum and not at all kept in sync with the Cygwin POSIX
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environment.</para>
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<para>If you need the full Win32 environment set up in a Cygwin process,
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you have to call</para>
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<screen>
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#include <sys/cygwin.h>
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cygwin_internal (CW_SYNC_WINENV);
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</screen>
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<para>to synchronize the Win32 environment with the Cygwin environment.
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Note that this only synchronizes the Win32 environment once with the
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Cygwin environment. Later changes using the <function>setenv</function>
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or <function>putenv</function> calls are not reflected in the Win32
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environment. In these cases, you have to call the aforementioned
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<function>cygwin_internal</function> call again.</para>
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</sect2>
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</sect1>
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