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2.3 Environment variables

In interactive mode, or when given the -V option (the default under MSDOS), Asymptote will automatically invoke the PostScript viewer gv (under UNIX) or gsview (under MSDOS; available from http://www.cs.wisc.edu/~ghost/gsview/) to display graphical output. These defaults may be overridden with the optional environment variable ASYMPTOTE_PSVIEWER. For PDF format output, the ASYMPTOTE_GS environment variable specifies the location of the PostScript-to-PDF processor gs and ASYMPTOTE_PDFVIEWER specifies the location of the PDF viewer. The graphical user interface may also required setting the variable ASYMPTOTE_PYTHON if python is installed in a nonstandard location. Here are the default values of these environment variables: 

UNIX:
export ASYMPTOTE_PSVIEWER=gv
export ASYMPTOTE_PDFVIEWER=acroread
export ASYMPTOTE_GS=gs
export ASYMPTOTE_PYTHON=

MSDOS:
set ASYMPTOTE_PSVIEWER=c:\Program Files\Ghostgum\gsview\gsview32.exe
set ASYMPTOTE_PDFVIEWER=
              c:\Program Files\Adobe\Acrobat 7.0\Reader\AcroRd32.exe
set ASYMPTOTE_GS=c:\Program Files\gs\gs8.51\bin\gswin32.exe
set ASYMPTOTE_PYTHON=c:\Python24\python.exe

To set environment variables under Microsoft Windows XP:

  1. Click on the Start button.
  2. Right-click on My Computer.
  3. Choose Properties from the popup menu.
  4. Click the Advanced tab.
  5. Click the Environment Variables button.

The following environment variables normally do not require adjustment: 

ASYMPTOTE_LATEX
ASYMPTOTE_DVIPS
ASYMPTOTE_CONVERT
ASYMPTOTE_DISPLAY
ASYMPTOTE_ANIMATE
ASYMPTOTE_XASY

To properly support interactive mode, the PostScript viewer should be capable of automatically redrawing whenever the output file is updated. The default PostScript viewer gv supports this (via a SIGHUP signal). Users of ggv will need to enable Watch file under Edit/Postscript Viewer Preferences and gsview users will need to enable Options/Auto Redisplay (however, under MSDOS it is still necessary to click on the gsview window; under UNIX one must manually redisplay by pressing the r key).

The patches supplied in the patches directory fix known bugs in the UNIX PostScript viewer gv-3.5.8 and gv-3.6.1 (most notably the backwards-incompatible command line options of gv-3.6.1). Another bug in gv-3.6.1 requires it to be explicitly configured with ./configure --enable-signal-handle for it to work properly with Asymptote's interactive mode.