lpr improvement proposal

["Rodrigo Medina" <rodmedina at cantv dot net>]

Hi all,
Now that the new version (1.2.4-1) of lpr works properly I have been trying
to
configure the printing commands of programs that can print directly,
such as dvips, ghostview or xfig. I have found that this task is not 
trivial because in general the files to be printed need to be preprocessed;
for example in my case they need to be converted from postscript to deskjet.
Not even the printing of a text file is trivial.

In order to facilitate this task I have modified lpr including a couple
of additional options. I am proposing to include these chages in the
new versions of lpr. Follows a description of the modifications. The
modified files are attached.

1-  In my experience most of the time the CR/LF translation is not needed,
 so it was flipped the way the raw option works. No option: raw printing,
 -l option: LF -> CR-LF preprocessing.

2- The -f option was included. It indicates that a FORMFEED character 
is appended to the file. In most printers (working in line printer mode)
this would produce the ejection of the last page of the document.

3- The " -F nameoffilter" to give the name of a filter (or pipe),
to be applied to the input file before sending it to the printer. So
   lpr -l -Ffilter -Pprinter file
would be equivalent to
   filter < file | lpr -l -Pprinter .

Follows a description of how to print different kinds of files on different
kinds of hardware if lpr had the features I am proposing.

	
--- Printing of text files with line-printers.

 In a Cygwin environment one has at least three kinds of text files: Unix
text
files, Windows text files and DOS text files. Unix and Windows text files
usually use some iso-8859-* character set, while DOS uses an ibm-cp*
character
set.  On the other hand Windows and DOS text files use CR-LF line
terminations,
while Unix files use LF line terminations. Most printers have a line-printer
mode in which they print each byte of a text file. In many cases, such as in
mine, the printer is DOS-compatible, what that means is that it uses an
ibm-cp*
character set, depending on the language you use, and of course it requires
a
CR-LF or LF-CR line termination.
 In my case the printer and DOS use ibm-cp850, while cygwin and Windows use
iso-8859-1. In order to print a text file one has to:

for a  DOS text file:
 append FF, send raw to lpr;
for a Windows text file:
 translate iso-8859-1 to ibm-cp850, append FF, send raw to lpr;
for a Unix text file:
 translate iso-8859-1 to ibm-cp850, LF->CR-LF, append FF, send raw to lpr.

If lpr had the options I proposed (including the change of -l) and an
iso2ibm
filter were available the commands for printing text files were:

        lpr -f -Pprinter DOS.txt
        lpr -f -Fiso2ibm -Pprinter WINDOWS.txt
        lpr -f -Fiso2ibm -l -Pprinter UNIX.txt

Right now I have to use scripts in order to accomplish the same tasks.

There are line-printers that use the iso-8859-* character set, in that case
WINDOWS and UNIX text files don't need to be preprocessed, but  DOS file
would require an ibm2iso filter:

        lpr -f -Fibm2iso -Pprinter DOS.txt
        lpr -f -Pprinter WINDOWS.txt
        lpr -f -l -Pprinter UNIX.txt

--- Using a postscript printer.
To print a postscript file would be trivial
        lpr -Pprinter file.ps

To print a text file you need a formatting filter, that produces a
postscript
file from the text file. Call it txt2ps. txt2ps can be designed to process
both WINDOWS and UNIX files.
        
        lpr -Ftxt2ps file.txt

For a DOS.TWX file you would need to previously  apply an ibm2iso filter

        lpr -Fibm2iso|txt2ps DOS.txt 

--- Using other graphic printers.
Most modern printers have a graphic mode of operation, which use their
own graphic language. The printer I have is a HP color deskjet. The
ghostscript which is distributed by cygwin translate a postscript file
to any kind of other graphic languages. Using gs one can make a shell
script that behaves as a filter from pstscript to deskjet: ps2cdj.

Some examples of printing. 
In order to print the output of a program like Word with the option "print
to file" one only needs to send the file raw to the printer

        lpr -Pprinter file.cdj

For printing a postscript file

        lpr -Fps2cdj -Pprinter file.ps

For printing a text file in graphic mode

        lpr -Ftxt2ps|ps2cdj -Pprinter file.txt
        lpr -Fibm2iso|txt2ps|ps2cdj -Pprinter DOS.txt

----------------------------------------------------------------------------
-----------

Rodrigo Medina.

Attachment: Printer.hh
Description: Printer.hh

Attachment: Printer.cc
Description: Printer.cc

Attachment: lpr.cc
Description: lpr.cc

Attachment: lpr.1
Description: lpr.1

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