1 <sect1 id="using-cygwinenv"><title>The <envar>CYGWIN</envar> environment
4 <sect2 id="cygwinenv-implemented-options">
5 <title>Implemented options</title>
7 <para>The <envar>CYGWIN</envar> environment variable is used to configure
8 many global settings for the Cygwin runtime system. It contains the options
9 listed below, separated by blank characters. Many options can be turned off
10 by prefixing with <literal>no</literal>.</para>
12 <itemizedlist mark="bullet">
15 <para><envar>(no)dosfilewarning</envar> - If set, Cygwin will warn the
16 first time a user uses an "MS-DOS" style path name rather than a POSIX-style
17 path name. Defaults to set.</para>
21 <para><envar>(no)envcache</envar> - If set, environment variable
22 conversions (between Win32 and POSIX) are cached. Note that this may
23 cause problems if the mount table changes, as the cache is not invalidated
24 and may contain values that depend on the previous mount table
25 contents. Defaults to set.</para>
29 <para><envar>(no)export</envar> - If set, the final values of these
30 settings are re-exported to the environment as <envar>CYGWIN</envar> again.
31 Defaults to off.</para>
36 <envar>error_start:Win32filepath</envar> - if set, runs
37 <filename>Win32filepath</filename> when cygwin encounters a fatal error,
38 which is useful for debugging. <filename>Win32filepath</filename> is
39 usually set to the path to <command>gdb</command> or
40 <command>dumper</command>, for example
41 <filename>C:\cygwin\bin\gdb.exe</filename>.
42 There is no default set.
47 <para><envar>forkchunk:32768</envar> - causes <function>fork()</function>
48 to copy memory some number of bytes at a time, in the above example
49 32768 bytes (32Kb) at a time. The default is to copy as many bytes as
50 possible, which is preferable in most cases but may slow some older systems
56 <para><envar>proc_retry:n</envar> - causes <function>fork()</function> and
57 <function>exec*()</function> to retry n times when a child process fails
58 due to certain windows-specific errors. These errors usually occur when
59 processes are being started while a user is logging off.
64 <para><envar>(no)glob[:ignorecase]</envar> - if set, command line arguments
65 containing UNIX-style file wildcard characters (brackets, question mark,
66 asterisk, escaped with \) are expanded into lists of files that match
68 This is applicable only to programs running from a DOS command line prompt.
69 Default is set.</para>
70 <para>This option also accepts an optional <literal>[no]ignorecase</literal> modifer.
71 If supplied, wildcard matching is case insensitive. The default is <literal>noignorecase</literal></para>
75 <para><envar>(no)reset_com</envar> - if set, serial ports are reset
76 to 9600-8-N-1 with no flow control when used. This is done at open
77 time and when handles are inherited. Defaults to set.</para>
81 <para><envar>(no)strip_title</envar> - if set, strips the directory
82 part off the window title, if any. Default is not set.</para>
86 <para><envar>(no)title</envar> - if set, the title bar
87 reflects the name of the program currently running. Default is not
92 <para><envar>(no)tty</envar> - if set, Cygwin enables extra support
93 (i.e., termios) for UNIX-like ttys in the Windows console.
94 It is not compatible with some Windows programs.
95 Defaults to not set, in which case the tty is opened in text mode.
96 Note that this has been changed such that ^D works as
97 expected instead of ^Z, and is settable via <command>stty</command>.
98 This option must be specified before starting a Cygwin shell
99 and it cannot be changed in the shell. It should not be set when using
100 other terminals (i.e., rxvt or xterm).
105 <para><envar>(no)upcaseenv</envar> - if set, Cygwin converts all
106 environment variables to all-uppercase, when a Cygwin process is started
107 from a non-Cygwin native Windows process. This was the default behavior in
108 releases prior to Cygwin 1.7. If not set, Cygwin does not change the case
109 of environment variables, except for a restricted set to maintain minimal
110 backward compatibility and for correct handling of certain essential
111 variables. The current list of always uppercased variables is:</para>
124 PROCESSOR_ARCHITECTURE
137 <para>Defaults to not set.</para>
141 <para><envar>(no)winsymlinks</envar> - if set, Cygwin creates
142 symlinks as Windows shortcuts with a special header and the R/O attribute
143 set. If not set, Cygwin creates symlinks as plain files with a magic number,
144 a path and the system attribute set. Defaults to not set since plain
145 file symlinks are faster to write and faster to read.</para>
147 <para>Please note that symlinks created under Cygwin 1.7 or later are
148 not readable by older Cygwin releases because the new symlinks use UTF-16
149 to encode the target filename, while the old symlinks used the current
150 ANSI or OEM charset.</para>
157 <sect2 id="cygwinenv-removed-options">
158 <title>Obsolete options</title>
161 Certain CYGWIN options available in past releases have been removed in
162 Cygwin 1.7 for one reason or another. These obsolete options are listed
165 <itemizedlist mark="bullet">
168 <para><envar>(no)binmode</envar> - This option has been removed because
169 all file opens default to binary mode, unless the open mode has been specified
170 explicitly in the open(2) call.
175 <para><envar>check_case</envar> - This option has been removed in favor of
176 real case sensitivity and the per-mount option "posix=[0|1]". For more
177 information, read the documentation in <xref linkend="mount-table"></xref> and
178 <xref linkend="pathnames-casesensitive"></xref>.</para>
182 <para><envar>codepage:[ansi|oem]</envar> - This option controled
183 which character set is used for file and console operations. Since Cygwin
184 is now doing all character conversion by itself, depending on the
185 application call to the <function>setlocale()</function> function, and in
186 turn by the setting of the environment variables <envar>$LANG</envar>,
187 <envar>$LC_ALL</envar>, or <envar>$LC_CTYPE</envar>, this setting
188 became superfluous.</para>
192 <para><envar>(no)ntea</envar> - This option has been removed since it
193 only fakes security which is considered dangerous and useless. It also
194 created an uncontrollably large file on FAT and was entirely useless
199 <para><envar>(no)ntsec</envar> - This option has been removed in favor of
200 the per-mount option "acl"/"noacl". For more information, read the
201 documentation in <xref linkend="mount-table"></xref>.</para>
205 <para><envar>(no)server</envar> - Originally this option had to be
206 enabled on the client side to use features only available when running
207 <command>cygserver</command>. This option has been removed because Cygwin now
208 always tries to contact cygserver if a function is called which requires
209 cygserver being available. For more information, read the documentation
210 in <xref linkend="using-cygserver"></xref>.</para>
214 <para><envar>(no)smbntsec</envar> - This option has been removed in favor of
215 the per-mount option "acl"/"noacl". For more information, read the
216 documentation in <xref linkend="mount-table"></xref>.</para>
220 <para><envar>(no)transparent_exe</envar> - This option has been removed
221 because the behaviour it switched on is now the standard behaviour in
226 <para><envar>(no)traverse</envar> - This option has been removed because
227 traverse checking is not quite correctly implemented by Microsoft and
228 it's behaviour has been getting worse with each new OS version. This
229 complicates its usage so the option has been removed for now.</para>