2 @appendix Configuring PSPP
4 @cindex PSPP, configuring
6 This chapter describe how to configure PSPP for your system.
9 * File locations:: How PSPP finds config files.
10 * Configuration techniques:: Many different methods of configuration...
11 * Configuration files:: How configuration files are read.
12 * Environment variables:: All about environment variables.
13 * Output devices:: Describing your terminal(s) and printer(s).
14 * Cairo driver class:: Configuration of Cairo devices.
15 * ASCII driver class:: Configuration of character-code devices.
16 * HTML driver class:: Configuration for HTML output.
17 * PostScript driver class:: Configuration of PostScript devices.
18 * Miscellaneous configuring:: Even more configuration variables.
22 @section Locating configuration files
24 PSPP searches each directory in the configuration file path for most
25 configuration files. The default configuration file path searches first
26 @file{$HOME/.pspp}, then the package system configuration directory (usually
27 @file{/usr/local/etc/pspp} or @file{/etc/pspp}). The value of
28 environment variable @env{PSPP_CONFIG_PATH}, if defined, overrides this
29 default path. Finally, @samp{-B @var{path}} or
30 @samp{--config-dir=@var{path}} specified on the command line has highest
33 @node Configuration techniques
34 @section Configuration techniques
36 There are many ways that PSPP can be configured. These are
37 described in the list below. Values given by earlier items take
38 precedence over those given by later items.
42 Syntax commands that modify settings, such as @cmd{SET}. @xref{SET}.
45 Command-line options. @xref{Invocation}.
48 PSPP-specific environment variable contents. @xref{Environment
52 General environment variable contents. @xref{Environment variables}.
55 Configuration file contents. @xref{Configuration files}.
61 Some of the above may not apply to a particular setting.
63 @node Configuration files
64 @section Configuration files
66 Most configuration files have a common form:
70 Each line forms a separate command or directive. This means that lines
71 cannot be broken up, unless they are spliced together with a trailing
72 backslash, as described below.
75 Before anything else is done, trailing white space is removed.
78 When a line ends in a backslash (@samp{\}), the backslash is removed,
79 and the next line is read and appended to the current line.
83 White space preceding the backslash is retained.
86 This rule continues to be applied until the line read does not end in a
90 It is an error if the last line in the file ends in a backslash.
94 Comments are introduced by an octothorpe (@samp{#}), and continue until the
99 An octothorpe inside balanced pairs of double quotation marks (@samp{"})
100 or single quotation marks (@samp{'}) does not introduce a comment.
103 The backslash character can be used inside balanced quotes of either
104 type to escape the following character as a literal character.
106 (This is distinct from the use of a backslash as a line-splicing
110 Line splicing takes place before comment removal.
114 Blank lines, and lines that contain only white space, are ignored.
117 @node Environment variables
118 @section Environment variables
120 You may think the concept of environment variables is a fairly simple
121 one. However, the author of PSPP has found a way to complicate
122 even something so simple. Environment variables are further described
123 in the sections below:
126 * Environment substitutions:: How environment substitutions are made.
127 * Predefined variables:: A few variables are automatically defined.
130 @node Environment substitutions
131 @subsection Environment substitutions
133 Much of the power of environment variables lies in the way that they may
134 be substituted into configuration files. Variable substitutions are
137 The line is scanned from left to right. In this scan, all characters
138 other than dollar signs (@samp{$}) are retained without change. Dollar
139 signs introduce environment variable references. References
144 Replaced by the value of environment variable @var{var}. @var{var} must
145 consist of either one or more letters, or exactly one non-alphabetic
146 character other than a left brace (@samp{@{}).
149 Same as above, but @var{var} may contain any character (except
153 Replaced by a single dollar sign.
156 Undefined variables expand to a empty value.
158 @node Predefined variables
159 @subsection Predefined environment variables
161 There are two environment variables predefined for use in environment
166 Defined as the version number of PSPP, as a string, in a format
167 something like @samp{0.9.4}.
170 Defined as the host architecture of PSPP, as a string, in standard
171 cpu-manufacturer-OS format. For instance, Debian GNU/Linux 1.1 on an
172 Intel machine defines this as @samp{i586-unknown-linux}. This is
173 somewhat dependent on the system used to compile PSPP.
176 Nothing prevents these values from being overridden, although it's a
177 good idea not to do so.
180 @section Output devices
182 Configuring output devices is the most complicated aspect of configuring
183 PSPP. The output device configuration file is named
184 @file{devices}. It is searched for using the usual algorithm for
185 finding configuration files (@pxref{File locations}). Each line in the
186 file is read in the usual manner for configuration files
187 (@pxref{Configuration files}).
189 Lines in @file{devices} are divided into three categories, described
190 briefly in the table below:
193 @item driver category definitions
194 Define a driver in terms of other drivers.
196 @item macro definitions
197 Define environment variables local to the output driver
200 @item device definitions
201 Describe the configuration of an output device.
204 The following sections further elaborate the contents of the
208 * Driver categories:: How to organize the driver namespace.
209 * Macro definitions:: Environment variables local to @file{devices}.
210 * Device definitions:: Output device descriptions.
211 * Dimensions:: Lengths, widths, sizes, @enddots{}
212 * Distinguishing line types:: Details on @file{devices} parsing.
213 * Tokenizing lines:: Dividing @file{devices} lines into tokens.
216 @node Driver categories
217 @subsection Driver categories
219 Drivers can be divided into categories. Drivers are specified by their
220 names, or by the names of the categories that they are contained in.
221 Only certain drivers are enabled each time PSPP is run; by
222 default, these are the drivers in the category `default'. To enable a
223 different set of drivers, use the @samp{-o @var{device}} command-line
224 option (@pxref{Invocation}).
226 Categories are specified with a line of the form
227 @samp{@var{category}=@var{driver1} @var{driver2} @var{driver3} @var{@dots{}}
228 @var{driver@var{n}}}. This line specifies that the category
229 @var{category} is composed of drivers named @var{driver1},
230 @var{driver2}, and so on. There may be any number of drivers in the
231 category, from zero on up.
233 Categories may also be specified on the command line
234 (@pxref{Invocation}).
236 This is all you need to know about categories. If you're still curious,
239 First of all, the term `categories' is a bit of a misnomer. In fact,
240 the internal representation is nothing like the hierarchy that the term
241 seems to imply: a linear list is used to keep track of the enabled
244 When PSPP first begins reading @file{devices}, this list contains
245 the name of any drivers or categories specified on the command line, or
246 the single item `default' if none were specified.
248 Each time a category definition is specified, the list is searched for
249 an item with the value of @var{category}. If a matching item is found,
250 it is deleted. If there was a match, the list of drivers (@var{driver1}
251 through @var{driver@var{n}}) is then appended to the list.
253 Each time a driver definition line is encountered, the list is searched.
254 If the list contains an item with that driver's name, the driver is
255 enabled and the item is deleted from the list. Otherwise, the driver
258 It is an error if the list is not empty when the end of @file{devices}
261 @node Macro definitions
262 @subsection Macro definitions
264 Macro definitions take the form @samp{define @var{macroname}
265 @var{definition}}. In such a macro definition, the environment variable
266 @var{macroname} is defined to expand to the value @var{definition}.
267 Before the definition is made, however, any macros used in
268 @var{definition} are expanded.
270 Please note the following nuances of macro usage:
274 For the purposes of this section, @dfn{macro} and @dfn{environment
275 variable} are synonyms.
278 Macros may not take arguments.
281 Macros may not recurse.
284 Macros are just environment variable definitions like other environment
285 variable definitions, with the exception that they are limited in scope
286 to the @file{devices} configuration file.
289 Macros override other all environment variables of the same name (within
290 the scope of @file{devices}).
293 Earlier macro definitions for a particular @var{key} override later
294 ones. In particular, macro definitions on the command line override
295 those in the device definition file. @xref{Non-option Arguments}.
298 There are two predefined macros, whose values are determined at runtime:
302 Defined as the width of the console screen, in columns of text.
305 Defined as the length of the console screen, in lines of text.
309 @node Device definitions
310 @subsection Driver definitions
312 Driver definitions are the ultimate purpose of the @file{devices}
313 configuration file. These are where the real action is. Driver
314 definitions tell PSPP where it should send its output.
316 Each driver definition line is divided into four fields. These fields
317 are delimited by colons (@samp{:}). Each line is subjected to
318 environment variable interpolation before it is processed further
319 (@pxref{Environment substitutions}). From left to right, the four
320 fields are, in brief:
324 A unique identifier, used to determine whether to enable the driver.
327 One of the predefined driver classes supported by PSPP. The
328 currently supported driver classes include `cairo' and `ascii'.
331 Zero or more of the following keywords, delimited by spaces:
336 Indicates that the device is a screen display. This may reduce the
337 amount of buffering done by the driver, to make interactive use more
342 Indicates that the device is a printer.
346 Indicates that the device is a listing file.
349 These options are just hints to PSPP and do not cause the output to be
350 directed to the screen, or to the printer, or to a listing file---those
351 must be set elsewhere in the options. They are used primarily to decide
352 which devices should be enabled at any given time. @xref{SET}, for more
356 An optional set of options to pass to the driver itself. The exact
357 format for the options varies among drivers.
360 The driver is enabled if:
364 Its driver name is specified on the command line, or
367 It's in a category specified on the command line, or
370 If no categories or driver names are specified on the command line, it
371 is in category @code{default}.
374 For more information on driver names, see @ref{Driver categories}.
376 The class name must be one of those supported by PSPP. The
377 classes supported depend on the options with which PSPP was
378 compiled. See later sections in this chapter for descriptions of the
379 available driver classes.
381 Options are dependent on the driver. See the driver descriptions for
385 @subsection Dimensions
387 Quite often in configuration it is necessary to specify a length or a
388 size. PSPP uses a common syntax for all such, calling them
389 collectively by the name @dfn{dimensions}.
393 You can specify dimensions in decimal form (@samp{12.5}) or as
394 fractions, either as mixed numbers (@samp{12-1/2}) or raw fractions
398 A number of different units are available. These are suffixed to the
399 numeric part of the dimension. There must be no spaces between the
400 number and the unit. The available units are identical to those offered
401 by the popular typesetting system @TeX{}:
405 inch (1 @code{in} = 2.54 @code{cm})
408 inch (1 @code{in} = 2.54 @code{cm})
411 printer's point (1 @code{in} = 72.27 @code{pt})
414 pica (12 @code{pt} = 1 @code{pc})
417 PostScript point (1 @code{in} = 72 @code{bp})
423 millimeter (10 @code{mm} = 1 @code{cm})
426 didot point (1157 @code{dd} = 1238 @code{pt})
429 cicero (1 @code{cc} = 12 @code{dd})
432 scaled point (65536 @code{sp} = 1 @code{pt})
436 If no explicit unit is given, PSPP attempts to guess the best unit:
440 Numbers less than 50 are assumed to be in inches.
443 Numbers 50 or greater are assumed to be in millimeters.
447 @node Distinguishing line types
448 @subsection How lines are divided into types
450 The lines in @file{devices} are distinguished in the following manner:
454 Leading white space is removed.
457 If the resulting line begins with the exact string @code{define},
458 followed by one or more white space characters, the line is processed as
462 Otherwise, the line is scanned for the first instance of a colon
463 (@samp{:}) or an equals sign (@samp{=}).
466 If a colon is encountered first, the line is processed as a driver
470 Otherwise, if an equals sign is encountered, the line is processed as a
474 Otherwise, the line is ill-formed.
477 @node Tokenizing lines
478 @subsection How lines are divided into tokens
480 Each driver definition line is run through a simple tokenizer. This
481 tokenizer recognizes two basic types of tokens.
483 The first type is an equals sign (@samp{=}). Equals signs are both
484 delimiters between tokens and tokens in themselves.
486 The second type is an identifier or string token. Identifiers and
487 strings are equivalent after tokenization, though they are written
488 differently. An identifier is any string of characters other than
489 white space or equals sign.
491 A string is introduced by a single- or double-quote character (@samp{'}
492 or @samp{"}) and, in general, continues until the next occurrence of
493 that same character. The following standard C escapes can also be
494 embedded within strings:
498 A single-quote (@samp{'}).
501 A double-quote (@samp{"}).
504 A question mark (@samp{?}). Included for hysterical raisins.
507 A backslash (@samp{\}).
510 Audio bell (ASCII 7).
522 Carriage return (ASCII 13).
528 Vertical tab (ASCII 11).
530 @item \@var{o}@var{o}@var{o}
531 Each @samp{o} must be an octal digit. The character is the one having
532 the octal value specified. Any number of octal digits is read and
533 interpreted; only the lower 8 bits are used.
535 @item \x@var{h}@var{h}
536 Each @samp{h} must be a hex digit. The character is the one having the
537 hexadecimal value specified. Any number of hex digits is read and
538 interpreted; only the lower 8 bits are used.
541 Tokens, outside of quoted strings, are delimited by white space or equals
544 @node Cairo driver class
545 @section The Cairo driver class
547 The @code{cairo} driver class can produce output in PDF, PostScript,
548 and SVG formats. It has full support for international character
551 The Cairo driver is only available if your copy of PSPP was built with
554 The available options are listed below.
557 @item output-file=@var{file-name}
559 File to which output should be sent. Default: @code{"pspp.pdf"}.
561 @item output-type=@var{output-type}
563 Type of output to write to the output file, one of @code{pdf},
564 @code{ps}, or @code{svg}. Default: @code{pdf}.
566 @item paper-size=@var{paper-size}
568 Paper size. You may specify a name (e.g.@: @code{a4}, @code{letter})
569 or measurements (e.g.@: @code{210x297}, @code{8.5x11in}).
571 The default paper size is taken from the @env{PAPERSIZE} environment
572 variable or the file indicated by the @env{PAPERCONF} environment
573 variable, if either variable is set. If not, and your system supports
574 the @code{LC_PAPER} locale category, then the default paper size is
575 taken from the locale. Otherwise, if @file{/etc/papersize} exists,
576 the default paper size is read from it. As a last resort, A4 paper is
579 @item orientation=@var{orientation}
581 Either @code{portrait} or @code{landscape}. Default: @code{portrait}.
583 @item headers=@var{boolean}
585 Controls whether the standard headers showing the time and date and
586 title and subtitle are printed at the top of each page. Default:
589 @item left-margin=@var{dimension}
590 @itemx right-margin=@var{dimension}
591 @itemx top-margin=@var{dimension}
592 @itemx bottom-margin=@var{dimension}
594 Sets the margins around the page. The headers, if enabled, are not
595 included in the margins; they are in addition to the margins. For a
596 description of dimensions, see @ref{Dimensions}. Default: @code{0.5in}.
598 @item prop-font=@var{font-name}
599 @itemx emph-font=@var{font-name}
600 @itemx fixed-font=@var{font-name}
602 Sets the font used for proportional, emphasized, or fixed-pitch text.
603 Most systems support CSS-like font names such as ``serif'' and
604 ``monospace'', but a wide range of system-specific font are likely to
605 be supported as well.
607 Default: proportional font @code{serif}, emphasis font @code{serif
608 italic}, fixed-pitch font @code{monospace}.
610 @item font-size=@var{font-size}
612 Sets the size of the default fonts, in thousandths of a point. Default:
615 @item line-gutter=@var{dimension}
617 Sets the width of white space on either side of lines that border text
618 or graphics objects. @xref{Dimensions}. Default: @code{1pt}.
620 @item line-spacing=@var{dimension}
622 Sets the spacing between the lines in a double line in a table.
625 @item line-width=@var{dimension}
627 Sets the width of the lines used in tables. Default: @code{0.5pt}.
630 @node ASCII driver class
631 @section The ASCII driver class
633 The ASCII driver class produces output that can be displayed on a
634 terminal or output to printers. The ASCII driver has class name
637 The available options are listed below.
640 @item output-file=@var{file-name}
642 File to which output should be sent. This can be an ordinary file name
643 (e.g., @code{"pspp.txt"}), a pipe (e.g., @code{"|more"}), or
644 stdout (@code{"-"}). Default: @code{"pspp.list"}.
646 @item chart-files=@var{file-name-template}
647 Template for the file names used for charts. The name should contain
648 a single @samp{#}, which is replaced by the chart number. Default:
651 @item chart-type=@var{type}.
652 Type of charts to output, either @samp{png} or @samp{none}.
655 Charts are always disabled if your installation of PSPP was compiled
656 without the @code{cairo} library.
658 @item paginate=@var{boolean}
660 If set, a formfeed will be written at the end of every page. Default:
663 @item tab-width=@var{tab-width-value}
665 The distance between tab stops for this device. If set to 0, tabs will
666 not be used in the output. Default: @code{8}.
668 @item headers=@var{boolean}
670 If enabled, two lines of header information giving title and subtitle,
671 page number, date and time, and PSPP version are printed at the top of
672 every page. These two lines are in addition to any top margin
673 requested. Default: @code{on}.
675 @item length=@var{line-count}
677 Physical length of a page. Headers and margins are subtracted from
678 this value. You may specify the number of lines as a number, or for
679 screen output you may specify @code{auto} to track the height of the
680 terminal as it changes. Default: @code{66}.
682 @item width=@var{character-count}
684 Physical width of a page. Margins are subtracted from this value.
685 You may specify the width as a number of characters, or for screen
686 output you may specify @code{auto} to track the width of the terminal
687 as it changes. Default: @code{79}.
689 @item top-margin=@var{top-margin-lines}
691 Length of the top margin, in lines. PSPP subtracts this value from
692 the page length. Default: @code{2}.
694 @item bottom-margin=@var{bottom-margin-lines}
696 Length of the bottom margin, in lines. PSPP subtracts this value from
697 the page length. Default: @code{2}.
699 @item box[@var{line-type}]=@var{box-chars}
701 The characters used for lines in tables produced by the ASCII driver can
702 be changed using this option. @var{line-type} is used to indicate which
703 type of line to change; @var{box-chars} is the character or string of
704 characters to use for this type of line.
706 @var{line-type} must be a 4-digit number. The digits are in the order
707 `right', `bottom', `left', `top'. The possibilities for each digit are:
725 Sets @samp{|} as the character to use for a single-width line with
726 bottom and top components.
730 Sets @samp{#} as the character to use for the intersection of four
731 double-width lines, one each from the top, bottom, left and right.
733 @item box[1100]="\xda"
735 Sets @samp{"\xda"}, which under MS-DOS is a box character suitable for
736 the top-left corner of a box, as the character for the intersection of
737 two single-width lines, one each from the right and bottom.
749 @*@code{box[0010]="-"}
750 @*@code{box[1010]="-"}
754 @*@code{box[0001]="|"}
755 @*@code{box[0101]="|"}
759 @*@code{box[0020]="="}
760 @*@code{box[2020]="="}
764 @*@code{box[0030]="="}
765 @*@code{box[3030]="="}
768 For all others, @samp{+} is used unless there are double lines or
769 special lines, in which case @samp{#} is used.
772 @item init=@var{init-string}
773 If set, this string is written at the beginning of each output file.
774 It can be used to initialize device features, e.g.@: to enable VT100
775 line-drawing characters.
777 @item emphasis=@var{emphasis-style}
779 How to emphasize text. Your choices are @code{bold}, @code{underline},
780 or @code{none}. Bold and underline emphasis are achieved with
781 overstriking, which may not be supported by all the software to which
782 you might pass the output.
785 @node HTML driver class
786 @section The HTML driver class
788 The @code{html} driver class is used to produce output for viewing in
789 tables-capable web browsers such as Emacs' w3-mode. Its configuration
790 is very simple. Currently, the output has a very plain format. In the
791 future, further work may be done on improving the output appearance.
793 There are only a few options:
796 @item output-file=@var{file-name}
798 File to which output should be sent. This can be an ordinary file name
799 (i.e., @code{"pspp.ps"}), a pipe (i.e., @code{"|lpr"}), or
800 stdout (@code{"-"}). Default: @file{"pspp.html"}.
802 @item chart-files=@var{file-name-template}
803 Template for the file names used for charts, which are output in PNG
804 format. The name should contain a single @samp{#}, which is replaced by
805 the chart number. Default: @file{"pspp-#.png"}.
808 @node PostScript driver class
809 @section The PostScript driver class
811 The @code{postscript} driver class is used to produce output that is
812 acceptable to PostScript printers and other interpreters.
813 The PostScript driver class does not support charts.
815 The PostScript driver class is deprecated. It is likely to be removed
816 in a future version of PSPP. We suggest that you use the Cairo driver
817 class instead, which can output PostScript as well and has better font
818 support, including support for international character sets, and does
821 The available options are listed below.
824 @item output-file=@var{file-name}
826 File to which output should be sent. This can be an ordinary file name
827 (i.e., @code{"pspp.ps"}), a pipe (i.e., @code{"|lpr"}), or
828 stdout (@code{"-"}). Default: @code{"pspp.ps"}.
830 @item headers=@var{boolean}
832 Controls whether the standard headers showing the time and date and
833 title and subtitle are printed at the top of each page. Default:
836 @item paper-size=@var{paper-size}
838 Paper size. You may specify a name (e.g.@: @code{a4}, @code{letter})
839 or measurements (e.g.@: @code{210x297}, @code{8.5x11in}).
841 The default paper size is taken from the @env{PAPERSIZE} environment
842 variable or the file indicated by the @env{PAPERCONF} environment
843 variable, if either variable is set. If not, and your system supports
844 the @code{LC_PAPER} locale category, then the default paper size is
845 taken from the locale. Otherwise, if @file{/etc/papersize} exists,
846 the default paper size is read from it. As a last resort, A4 paper is
849 @item orientation=@var{orientation}
851 Either @code{portrait} or @code{landscape}. Default: @code{portrait}.
853 @item left-margin=@var{dimension}
854 @itemx right-margin=@var{dimension}
855 @itemx top-margin=@var{dimension}
856 @itemx bottom-margin=@var{dimension}
858 Sets the margins around the page. The headers, if enabled, are not
859 included in the margins; they are in addition to the margins. For a
860 description of dimensions, see @ref{Dimensions}. Default: @code{0.5in}.
862 @item prop-font=@var{afm-file}[,@var{font-file}[,@var{encoding-file}]]
863 @itemx emph-font=@var{afm-file}[,@var{font-file}[,@var{encoding-file}]]
864 @itemx fixed-font=@var{afm-file}[,@var{font-file}[,@var{encoding-file}]]
866 Sets the font used for proportional, emphasized, or fixed-pitch text.
867 The only required value is @var{afm-file}, the AFM file for the font.
869 If specified, @var{font-file} will be downloaded to the printer at the
870 beginning of the print job. The font file may be in PFA or PFB format.
872 The font is reencoded as specified in @var{encoding-file}, if specified.
873 Each line in @var{encoding-file} should consist of a PostScript
874 character name and a decimal encoding value (between 0 and 255),
875 separated by white space. Blank lines and comments introduced by
876 @samp{#} are also allowed.
878 The files specified on these options are located as follows. If
879 the file name begins with @samp{/}, then it is taken as an absolute
880 path. Otherwise, PSPP searches its configuration path for the specified
881 name prefixed by @code{psfonts/} (@pxref{File locations}).
883 Default: proportional font @code{Times-Roman.afm}, emphasis font
884 @code{Times-Italic.afm}, fixed-pitch font @code{Courier.afm}.
886 @item font-size=@var{font-size}
888 Sets the size of the default fonts, in thousandths of a point. Default:
891 @item line-gutter=@var{dimension}
893 Sets the width of white space on either side of lines that border text
894 or graphics objects. @xref{Dimensions}. Default: @code{1pt}.
896 @item line-spacing=@var{dimension}
898 Sets the spacing between the lines in a double line in a table.
901 @item line-width=@var{dimension}
903 Sets the width of the lines used in tables. Default: @code{0.5pt}.
906 @node Miscellaneous configuring
907 @section Miscellaneous configuration
909 The following environment variables can be used to further configure
915 Used to determine the user's home directory. No default value.
917 @item STAT_INCLUDE_PATH
919 Path used to find include files in PSPP syntax files. Defaults vary
920 across operating systems:
930 @file{$HOME/.pspp/include}
933 @file{/usr/local/lib/pspp/include}
936 @file{/usr/lib/pspp/include}
939 @file{/usr/local/share/pspp/include}
942 @file{/usr/share/pspp/include}
952 @file{C:\PSPP\INCLUDE}
964 The terminal type @code{termcap} or @code{ncurses} will use, if such
965 support was compiled into PSPP.
967 @item STAT_OUTPUT_INIT_FILE
969 The basename used to search for the driver definition file.
970 @xref{Output devices}. @xref{File locations}. Default: @code{devices}.
972 @item STAT_OUTPUT_INIT_PATH
974 The path used to search for the driver definition file.
975 @xref{File locations}. Default: the standard configuration path.
979 The directory in which PSPP stores its temporary files (used when sorting
980 cases or concatenating large numbers of cases).
981 Default: (UNIX) @file{/tmp}, (MS-DOS) @file{\}, (other OSes) empty string.
986 Under MS-DOS only, these variables are consulted after TMPDIR, in this