lp(7)
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lp, lpj Special File
Eclipse MV/family line printer special files
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DESCRIPTION
The character special devices lp and lpj provide access to line
printer devices. Both drivers provide the same interface and
support all current printer models. The lpj driver is used on
the MV/1400, MV/2000, and DS/7500 series processors while the lp
driver is used on the MV/4000, MV/7800, MV/8000, MV/10000,
MV/15000, and MV/20000 series processors.
The printer driver takes the characters written to it and sends
them to the line printer hardware. If the printer hardware takes
special action in response to particular characters output to the
device, such as form feeds, the application may take advantage of
these features by outputting the appropriate characters, but
there are no dependencies on these features within the driver.
The driver does not perform any special paper spacing or other
forms control to handle paper folds, etc.
The open system call performs appropriate device dependent checks
to determine that the printer device is online and ready to
print; i.e., the printer must be ready to accept characters and
print them without further operator intervention. If the printer
is not ready, the error ENXIO is returned. A printer is an
exclusive open device; the error ENXIO is returned if an attempt
is made to open a printer that is already open.
For the close system call, user visible functionality is the same
as for an ordinary disk file.
The read system call is not supported. The error ENODEV is
always returned.
For the write system call, the contents of the caller's buffer
are sent to the physical line printer. If an error occurs on the
I/O, the error EIO is returned. If the printer is off-line when
a write is started, or goes off-line while a write is in
progress, the system call will pend until the printer is on-line
and the data is written.
The ioctl commands LPRFMTEN and LPRFMTDS give access to the
printer's format control memory. Normally, characters written to
the printer are printed on the paper under control of the
printer's format control memory. After issuing the LPRFMTEN
ioctl, all characters sent to the printer go into the printer's
format control memory instead of printing. The LPRFMTDS ioctl
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lp(7)
restores normal printing operation. The characters used to fill
the format control memory for a given application are line
printer model dependent, and some printers have no format control
memory. Unfortunately, it is not possible for software to
determine the type of printer or whether it has format control
memory. Issuing either of these ioctl calls on a printer with no
format control memory has no effect. A successful open always
performs an implicit LPRFMTDS ioctl.
Select always returns READY for both read and write operations.
FILES
/dev/lp*
/dev/lpj*
SEE ALSO
lp(1).
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