SCO Unix/System V Printing FAQ

How do I stop staircase output on a SCO Unix/System V printer?

This is caused by the different ways that DOS and Unix handle the end of a text line. Unix ends a line with a LF (Line Feed, 0x0A) character, while DOS uses both a LF and a CR (Carriage Return, 0x0D).

In Linux, your printer setup tool should offer this translation as an option.

Staircase is when you printer prints like this:

 Everything starts out OK, but when you reach 
                                              the end of a line, it moves
                                                                          down but not back

(With a laser printer, the same problem will cause only one or even no lines to print)

If a printer is expecting both characters, getting only a LF tells it to only do a Line Feed without a Carriage Return, so that's just what it does, and that's just what you get.

There are at least five ways to fix this:

  • Change the printer so that it generates a CR when it gets a line feed. Most printers can do this, and if you use it for DOS, it just means there is an "extra" CR, which changes nothing. This is done with dip switches or a printer configuration panel.
  • Change the printer by sending it whatever escape sequences it needs to add CR's to LF's. This is going to vary, and you are going to need to add it in the interface script low enough that it doesn't get reset by some other command being sent out.
  • (Linux)Filter the output through "todos". This involves piping the output through that on it's way out: " cat printfile.txt | todos | lpr". If you wanted to do more, perl -ne 'chop; print $_,"\r\n"' takes care of the translation part and you could add more.

  • (SCO) Filter the output through /usr/lib/lponlcr or xtod. This involves piping the output through that on it's way out. In the "standard" script, you might set "FILTER=/usr/lib/lponlcr". In other scripts, just add " | /usr/lib/lponlcr" on the line that cats the file.
  • (SCO) Set the "stty onlcr opost" in the interface script. This can be done from the printer manager on Release 4 and 5, or by using the "crnlmap" model; unfortunately it does not always work (for example, it can't work for network printers). See: /Unixart/netprint.html
  • (SCO) Move the "stty onlcr opost" to a "hold-open" script (see the article on serial printers) for this port. This works, but it's annoying, and again won't work for network printers.
  • (SCO) If you are using an HP network printer, you can add "-n" or even "-N" to the the interface. Don't add it to the "HPNPF=" line; add it in the line(s) that actually uses $HPNPF. For example, you'd change
         if $REALMODEL "$@" | $HPNPF -x $PERIPH 2> $LOG > /dev/null
         if $REALMODEL "$@" | $HPNPF -x $PERIPH -n 2> $LOG > /dev/null
    You can download See man hpnpf

David DiPieto offered these thoughts:

 Date: Tue, 29 Dec 1998 16:05:40 -0500
 From: David DiPietro <>
 Subject: printer stairstepping ...
 Content-Type: text/plain; charset=us-ascii
 Content-Transfer-Encoding: 7bit
 I thought I'd share a little opost experience with you.  When I install
 our application software I automatically add a "holdopen" for each
 parallel and serial printer to append the <cr> to <lf> as you mention in
 your printer discussion.  Most of our sites now involve some kind of
 networking and printer sharing.  I had been putting the high-speed
 lasers on the parallel ports on the SCO Unix server but starting having
 a problem with Windows applications printing graphics.  I would often
 loose data or get garbled graphics.  I finally decided to take the time
 to figure out what was going on using the hex dump mode on a Lexmark
 Laser.  Apparently, and with understanding, having opost onlcr turned on
 will do a straight binary filter of the printer data replacing all <nl>
 with <cr><nl> - even if it occurs in the middle of a raster graphics
 string.  This could - and will most likely - reak havoc on the output! 
 You may want to address this in your discussion.  In my case, the
 problem was solved completely by turning on the auto <cr> at the
 Dave DiPietro/Abacus Systems Inc.
 (973) 875-9900

Got something to add? Send me email.

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