Printing commands, such as lpr-buffer (see section Hardcopy Output) and
ps-print-buffer (see section Postscript Hardcopy) can work in MS-DOS by
sending the output to one of the printer ports, if a Unix-style lpr
program is unavailable. A few DOS-specific variables control how this
works.
If you want to use your local printer, printing on it in the usual DOS
manner, then set the Lisp variable dos-printer to the name of the
printer port--for example, "PRN", the usual local printer port
(that's the default), or "LPT2" or "COM1" for a serial
printer. You can also set dos-printer to a file name, in which
case "printed" output is actually appended to that file. If you set
dos-printer to "NUL", printed output is silently
discarded (sent to the system null device).
If you set dos-printer to a file name, it's best to use an
absolute file name. Emacs changes the working directory according to
the default directory of the current buffer, so if the file name in
dos-printer is relative, you will end up with several such files,
each one in the directory of the buffer from which the printing was
done.
The commands print-buffer and print-region call the
pr program, or use special switches to the lpr program, to
produce headers on each printed page. MS-DOS doesn't normally have
these programs, so by default, the variable lpr-headers-switches
is set so that the requests to print page headers are silently ignored.
Thus, print-buffer and print-region produce the same
output as lpr-buffer and lpr-region, respectively. If you
do have a suitable pr program (for example, from GNU Textutils),
set lpr-headers-switches to nil; Emacs will then call
pr to produce the page headers, and print the resulting output as
specified by dos-printer.
Finally, if you do have an lpr work-alike, you can set
print-region-function to nil. Then Emacs uses lpr
for printing, as on other systems. (If the name of the program isn't
lpr, set the lpr-command variable to specify where to find
it.)
A separate variable, dos-ps-printer, defines how PostScript
files should be printed. If its value is a string, it is used as the
name of the device (or file) to which PostScript output is sent, just as
dos-printer is used for non-PostScript printing. (These are two
distinct variables in case you have two printers attached to two
different ports, and only one of them is a PostScript printer.) If the
value of dos-ps-printer is not a string, then the variables
ps-lpr-command and ps-lpr-switches (see section Postscript Hardcopy)
control how to print PostScript files. Thus, if you have a
non-PostScript printer, you can set these variables to the name and the
switches appropriate for a PostScript interpreter program (such as
Ghostscript).
For example, to use Ghostscript for printing on an Epson printer connected to `LPT2' port, put this on your `.emacs' file:
(setq dos-ps-printer t) ; Anything but a string.
(setq ps-lpr-command "c:/gs/gs386")
(setq ps-lpr-switches '("-q" "-dNOPAUSE"
"-sDEVICE=epson"
"-r240x72"
"-sOutputFile=LPT2"
"-Ic:/gs"
"-"))
(This assumes that Ghostscript is installed in the `"c:/gs"' directory.)
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