G.9 Printing and MS-Windows
Printing commands, such as lpr-buffer (see Printing Hard Copies) and
ps-print-buffer (see PostScript Hardcopy) work in MS-DOS and
MS-Windows by sending the output to one of the printer ports, if a
POSIX-style lpr program is unavailable. The same Emacs
variables control printing on all systems, but in some cases they have
different default values on MS-DOS and MS-Windows.
Emacs on MS Windows attempts to determine your default printer
automatically (using the function default-printer-name).
But in some rare cases this can fail, or you may wish to use a different
printer from within Emacs. The rest of this section explains how to
tell Emacs which printer to use.
If you want to use your local printer, then set the Lisp variable
lpr-command to "" (its default value on Windows) and
printer-name to the name of the printer port—for example,
"PRN", the usual local printer port, or "LPT2", or
"COM1" for a serial printer. You can also set
printer-name to a file name, in which case “printed” output
is actually appended to that file. If you set printer-name to
"NUL", printed output is silently discarded (sent to the system
null device).
You can also use a printer shared by another machine by setting
printer-name to the UNC share name for that printer—for
example, "//joes_pc/hp4si". (It doesn’t matter whether you use
forward slashes or backslashes here.) To find out the names of shared
printers, run the command ‘ net view’ from the command prompt to
obtain a list of servers, and ‘ net view server-name’ to see
the names of printers (and directories) shared by that server.
Alternatively, click the ‘ Network Neighborhood’ icon on your
desktop, and look for machines that share their printers via the
network.
If the printer doesn’t appear in the output of ‘ net view’, or
if setting printer-name to the UNC share name doesn’t produce a
hardcopy on that printer, you can use the ‘ net use’ command to
connect a local print port such as "LPT2" to the networked
printer. For example, typing net use LPT2: \\joes_pc\hp4si 27
causes Windows to capture the LPT2 port and redirect the
printed material to the printer connected to the machine joes_pc.
After this command, setting printer-name to "LPT2"
should produce the hardcopy on the networked printer.
With some varieties of Windows network software, you can instruct
Windows to capture a specific printer port such as "LPT2", and
redirect it to a networked printer via the Control Panel->Printers applet instead of ‘ net use’.
If you set printer-name 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
printer-name is relative, you will end up with several such
files, each one in the directory of the buffer from which the printing
was done.
If the value of printer-name is correct, but printing does
not produce the hardcopy on your printer, it is possible that your
printer does not support printing plain text (some cheap printers omit
this functionality). In that case, try the PostScript print commands,
described below.
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 and MS-Windows don’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 Coreutils), set
lpr-headers-switches to nil; Emacs will then call
pr to produce the page headers, and print the resulting output as
specified by printer-name.
Finally, if you do have an lpr work-alike, you can set the
variable lpr-command to "lpr". Then Emacs will use
lpr for printing, as on other systems. (If the name of the
program isn’t lpr, set lpr-command to the appropriate value.)
The variable lpr-switches has its standard meaning
when lpr-command is not "". If the variable
printer-name has a string value, it is used as the value for the
-P option to lpr, as on Unix.
A parallel set of variables, ps-lpr-command,
ps-lpr-switches, and ps-printer-name (see Variables for PostScript Hardcopy), defines how PostScript files should be printed. These
variables are used in the same way as the corresponding variables
described above for non-PostScript printing. Thus, the value of
ps-printer-name is used as the name of the device (or file) to
which PostScript output is sent, just as printer-name is used
for non-PostScript printing. (There are two distinct sets of
variables in case you have two printers attached to two different
ports, and only one of them is a PostScript printer.)
The default value of the variable ps-lpr-command is "",
which causes PostScript output to be sent to the printer port specified
by ps-printer-name; but ps-lpr-command can also be set to
the name of a program which will accept PostScript files. Thus, if you
have a non-PostScript printer, you can set this variable to the name of
a PostScript interpreter program (such as Ghostscript). Any switches
that need to be passed to the interpreter program are specified using
ps-lpr-switches. (If the value of ps-printer-name is a
string, it will be added to the list of switches as the value for the
-P option. This is probably only useful if you are using
lpr, so when using an interpreter typically you would set
ps-printer-name to something other than a string so it is
ignored.)
For example, to use Ghostscript for printing on the system’s default
printer, put this in your .emacs file:
(setq ps-printer-name t)
(setq ps-lpr-command "D:/gs6.01/bin/gswin32c.exe")
(setq ps-lpr-switches '("-q" "-dNOPAUSE" "-dBATCH"
"-sDEVICE=mswinpr2"
"-sPAPERSIZE=a4"))
(This assumes that Ghostscript is installed in the
D:/gs6.01 directory.)
Footnotes
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Note that the ‘ net use’ command requires the UNC share name to be
typed with the Windows-style backslashes, while the value of
printer-name can be set with either forward- or backslashes.