The behavior of graph is affected by several environment
variables. We have already mentioned the environment variables
BITMAPSIZE, PAGESIZE, BG_COLOR, and
MAX_LINE_LENGTH. They serve as backups for the options
`--bitmap-size', `--page-size', `--bg-color', and
`--max-line-length'. The remaining environment variables are
specific to individual output formats.
graph -T X, which pops up a window on an X Window System
display and draws graphics in it, checks the DISPLAY
environment variable. The value of this variable determines the display
on which the window will be popped up.
graph -T pnm, which produces output in Portable Anymap
(PBM/PGM/PPM) format, is affected by the PNM_PORTABLE environment
variable. If its value is "yes", the output file will be in the
portable (human readable) version of PBM, PGM, or PPM format, rather
than the default (binary) version.
graph -T gif, which produces output in pseudo-GIF format, is
affected by two environment variables. If the value of the
INTERLACE variable is "yes", the pseudo-GIF output file will be
in interlaced format. Also, if the value of the
TRANSPARENT_COLOR environment variable is the name of a color
that appears in the output file, that color will be treated as
transparent by most applications that read GIF files. For information
on what color names are recognized, see section Specifying Colors by Name.
graph -T pcl, which produces PCL 5 output for
Hewlett--Packard printers and plotters, is affected by several
environment variables. The position of the graphics display on the page
can be adjusted by setting the PCL_XOFFSET and PCL_YOFFSET
environment variables, which may be specified in centimeters,
millimeters, or inches. For example, an offset could be specified
as "2cm" or "1.2in". Also, the display can be rotated 90 degrees
counterclockwise on the page by setting the PCL_ROTATE
environment variable to "yes". This is not the same as the rotation
obtained with the --rotation option, which sets the rotation
angle of the plot within the display. Besides "no" and "yes",
recognized values for the PCL_ROTATE variable are "0", "90",
"180", and "270". "no" and "yes" are equivalent to "0" and
"90", respectively.
The variable PCL_ASSIGN_COLORS is also recognized. It should be
set to "yes" when producing PCL 5 output for a color printer or
other color device. This will ensure accurate color reproduction by
giving the output device complete freedom in assigning colors,
internally, to its "logical pens". If it is "no" then the device will
use a fixed set of colored pens, and will emulate other colors by
shading. The default is "no" because monochrome PCL 5 devices,
which are much more common than colored ones, must use shading to
emulate color.
graph -T hpgl, which produces Hewlett--Packard Graphics Language
output, is also affected by several environment variables. The most
important is HPGL_VERSION, which may be set to "1", "1.5", or
"2" (the default). "1" means that the output should be generic
HP-GL, "1.5" means that the output should be suitable for the
HP7550A graphics plotter and the HP758x, HP7595A and HP7596A drafting
plotters (HP-GL with some HP-GL/2 extensions), and "2" means that
the output should be modern HP-GL/2. If the version is "1" or
"1.5" then the only available fonts will be vector fonts, and all lines
will be drawn with a default thickness (the `-W' option will not
work). Additionally, if the version is "1" then the filling of
arbitrary curves with solid color will not be supported (the `-q'
option may be used to fill circles and rectangles aligned with the
coordinate axes, though).
The position of the graph -T hpgl graphics display on the page
can be adjusted by setting the HPGL_XOFFSET and
HPGL_YOFFSET environment variables, which may be specified in
centimeters, millimeters, or inches. For example, an offset could be
specified as "2cm" or "1.2in". Also, the display can be rotated 90
degrees counterclockwise on the page by setting the HPGL_ROTATE
environment variable to "yes". This is not the same as the rotation
obtained with the --rotation option, which sets the rotation
angle of the plot within the display. Besides "no" and "yes",
recognized values for the HPGL_ROTATE variable are "0", "90",
"180", and "270". "no" and "yes" are equivalent to "0" and
"90", respectively. "180" and "270" are supported only if
HPGL_VERSION is "2" (the default).
Opaque filling and the drawing of visible white lines are
supported only if HPGL_VERSION is "2" (the default) and the
environment variable HPGL_OPAQUE_MODE is "yes" (the default).
If the value is "no" then opaque filling will not be used, and white
lines (if any), which are normally drawn with pen #0, will not
be drawn. This feature is to accommodate older HP-GL/2 devices.
HP-GL/2 pen plotters, for example, do not support opacity or the use
of pen #0 to draw visible white lines. Some older HP-GL/2 devices
reportedly malfunction if asked to draw opaque objects.
By default, graph -T hpgl will draw with a fixed set of pens.
Which pens are present may be specified by setting the HPGL_PENS
environment variable. If HPGL_VERSION is "1", the default
value of HPGL_PENS is "1=black"; if HPGL_VERSION is "1.5"
or "2", the default value of HPGL_PENS is
"1=black:2=red:3=green:4=yellow:5=blue:6=magenta:7=cyan". The format
should be self-explanatory. By setting HPGL_PENS, you may
specify a color for any pen in the range #1...#31. For information
on what color names are recognized, see section Specifying Colors by Name. Pen #1
must always be present, though it need not be black. Any other pen in
the range #1...#31 may be omitted.
If HPGL_VERSION is "2" then graph -T hpgl will also be
affected by the environment variable HPGL_ASSIGN_COLORS. If
the value of this variable is "yes", then graph -T hpgl will not
be restricted to the palette specified in HPGL_PENS: it will
assign colors to "logical pens" in the range #1...#31, as
needed. The default value is "no" because other than color LaserJet
printers and DesignJet plotters, not many HP-GL/2 devices allow the
assignment of colors to logical pens.
graph -T tek, which produces output for a Tektronix terminal or
emulator, checks the TERM environment variable. If the value
of TERM is "xterm", "xterms", or "kterm", it is taken as a
sign that the current application is running in an X Window System
VT100 terminal emulator: an xterm. Before drawing graphics,
graph -T tek will emit an escape sequence that causes the
terminal emulator's auxiliary Tektronix window, which is normally
hidden, to pop up. After the graphics are drawn, an escape sequence
that returns control to the original VT100 window will be emitted. The
Tektronix window will remain on the screen.
If the value of TERM is "kermit", "ansi.sys", "ansissys",
"ansi.sysk", or "ansisysk", it is taken as a sign that the current
application is running in the VT100 terminal emulator provided by the
MS-DOS version of kermit. Before drawing graphics, graph
-T tek will emit an escape sequence that switches the terminal emulator
to Tektronix mode. Also, some of the Tektronix control codes emitted by
graph -T tek will be kermit-specific. There will be a
limited amount of color support, which is not normally the case (the 16
ansi.sys colors will be supported). After drawing graphics,
graph -T tek will emit an escape sequence that returns the
emulator to VT100 mode. The key sequence `ALT minus' can be
employed manually within kermit to switch between the two modes.
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