# phpman > man > lp(4)

[LP(4)](https://www.chedong.com/phpMan.php/man/LP/4/markdown)                                 Linux Programmer's Manual                                [LP(4)](https://www.chedong.com/phpMan.php/man/LP/4/markdown)



## NAME
       lp - line printer devices

## SYNOPSIS
### #include <linux/lp.h>

## CONFIGURATION
       **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 is polling.

## DESCRIPTION
       The following [**ioctl**(2)](https://www.chedong.com/phpMan.php/man/ioctl/2/markdown) calls are supported:

       **int** **ioctl(int** _fd_**,** **LPTIME,** **int** _arg_**)**
              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** _arg_**)**
              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** _arg_**)**
              If  _arg_  is 0, [**open**(2)](https://www.chedong.com/phpMan.php/man/open/2/markdown) will be aborted on error, otherwise error will be ignored.  The
              default is to ignore it.

       **int** **ioctl(int** _fd_**,** **LPCAREFUL,** **int** _arg_**)**
              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 ac‐
              cept 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 microsec‐
              onds, 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 inter‐
              rupt driver.

       **int** **ioctl(int** _fd_**,** **LPSETIRQ,** **int** _arg_**)**
              This [**ioctl**(2)](https://www.chedong.com/phpMan.php/man/ioctl/2/markdown) 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 also default.

       **int** **ioctl(int** _fd_**,** **LPGETIRQ,** **int** *****_arg_**)**
              Stores the currently used IRQ in _arg_.

       **int** **ioctl(int** _fd_**,** **LPGETSTATUS,** **int** *****_arg_**)**
              Stores the value of the status port in _arg_.  The bits have the following meaning:

              LP_PBUSY     inverted busy input, active high

              LP_PACK      unchanged acknowledge input, active low
              LP_POUTPA    unchanged out-of-paper input, active high
              LP_PSELECD   unchanged selected input, active high
              LP_PERRORP   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.

       **int** **ioctl(int** _fd_**,** **LPRESET)**
              Resets the printer.  No argument is used.

## FILES
       _/dev/lp*_

## SEE ALSO
       [**chmod**(1)](https://www.chedong.com/phpMan.php/man/chmod/1/markdown), [**chown**(1)](https://www.chedong.com/phpMan.php/man/chown/1/markdown), [**mknod**(1)](https://www.chedong.com/phpMan.php/man/mknod/1/markdown), [**lpcntl**(8)](https://www.chedong.com/phpMan.php/man/lpcntl/8/markdown), [**tunelp**(8)](https://www.chedong.com/phpMan.php/man/tunelp/8/markdown)

## COLOPHON
       This  page  is  part  of  release  5.10 of the Linux _man-pages_ project.  A description of the
       project, information about reporting bugs, and the latest version of this page, can be  found
       at <https://www.kernel.org/doc/man-pages/>.



Linux                                        2020-08-13                                        [LP(4)](https://www.chedong.com/phpMan.php/man/LP/4/markdown)