lp[0–2] are character devices for the parallel line printers; they
have major number 6 and minor number 0–2. The minor numbers correspond
to the printer port base addresses 0x03bc, 0x0378, and 0x0278. Usually they
have mode 220 and are owned by user root and group lp. You can
use printer ports either with polling or with interrupts. Interrupts are
recommended when high traffic is expected, for example, for laser printers.
For typical dot matrix printers, polling will usually be enough. The default
Sets the amount of time that the driver sleeps before rechecking the
printer when the printer's buffer appears to be filled to arg. If
you have a fast printer, decrease this number; if you have a slow printer,
then increase it. This is in hundredths of a second, the default 2 being
0.02 seconds. It influences only the polling driver.
int ioctl(int fd, LPCHAR, int arg)
Sets the maximum number of busy-wait iterations which the polling driver
does while waiting for the printer to get ready for receiving a character
to arg. If printing is too slow, increase this number; if the
system gets too slow, decrease this number. The default is 1000. It
influences only the polling driver.
int ioctl(int fd, LPABORT, int
If arg is 0, the printer driver will retry on errors, otherwise it
will abort. The default is 0.
int ioctl(int fd, LPABORTOPEN, int
If arg is 0, open(2) will be aborted on error, otherwise
error will be ignored. The default is to ignore it.
int ioctl(int fd, LPCAREFUL, int
If arg is 0, then the out-of-paper, offline, and error signals are
required to be false on all writes, otherwise they are ignored. The
default is to ignore them.
int ioctl(int fd, LPWAIT, int arg)
Sets the number of busy waiting iterations to wait before strobing the
printer to accept a just-written character, and the number of iterations
to wait before turning the strobe off again, to arg. The
specification says this time should be 0.5 microseconds, but experience
has shown the delay caused by the code is already enough. For that reason,
the default value is 0. This is used for both the polling and the
int ioctl(int fd, LPSETIRQ, int
This ioctl(2) requires superuser privileges. It takes an int
containing the new IRQ as argument. As a side effect, the printer will be
reset. When arg is 0, the polling driver will be used, which is
int ioctl(int fd, LPGETIRQ, int
Stores the currently used IRQ in arg.
int ioctl(int fd, LPGETSTATUS, int
Stores the value of the status port in arg. The bits have the
inverted busy input, active high
unchanged acknowledge input, active low
unchanged out-of-paper input, active high
unchanged selected input, active high
unchanged error input, active low
Refer to your printer manual for the meaning of the signals. Note that
undocumented bits may also be set, depending on your printer.
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