The principle and printing process of the printer under Linux __linux

Linux Printing principle
Under Linux, the spool (spooling) printing method, when the user needs to print a file, the file is not sent directly to the printer, but sent to the spool directory, and then a responsible for printing the background process to send the data into the printer.
Linux defines a print buffer for each printer, and the printer daemon scans the print buffer frequently to see if there are any new files to print. If present, the files in the buffer are printed in a first-in, first-out order.
In addition to being able to print on a local printer, the Linux system can also be printed remotely over a network printer.

The principles of printing on Linux systems are as follows:

Various types of documents are converted by one (or some) conversion program into a format that the printer is aware of, that is, a stream described in various types of printer languages, which are sent directly to the printer port and interpreted by the printer and form a hard copy.
Most Linux systems currently implement the conversion of document to printer language using the following process:

Ordinary text files and various types of graphics are converted to PostScript files by the appropriate conversion programs, and some applications write their output directly as PostScript files. These PostScript files are converted to the printer language via an application Ghostscript as a printer filter. Therefore, if the system's print system is already configured to use Ghostsript as a print filter, the application is to output a PostScript file that conforms to the program requirements and syntax.

Linux Print process

In the process of printing, it is usually the application that produces output and transmits it to LPR in a piped way or prints a file directly using LPR. LPR communicates with the printer background service program over the network and transmits the corresponding print data and printing options. The printer background Service program stores print information in the appropriate spooler directory and sends the print task to the print device when the output device is available.