The simplest way to print in Linux is to cat a file to the printing device, like this:

sudo cat my-file-to-print.txt > /dev/lp

What this command does is read the file my-file-to-print.txt and send it, byte by byte, to the printer device /dev/lp. (This name is a symbolic link to the device, and may vary. Your printer may be another device name, for instance lp0.) Normally cat sends its output to standard output (the terminal) but here we redirect it to the device /dev/lp with the > operator. Only the superuser can write directly to the printer device, which is why we have to preface the command with sudo.

lpr is much more user-friendly than this, however, and it allows you to queue print jobs. And most importantly, it allows you to access the printer device without being the superuser.

The way lpr works, in a nutshell, is: it reads in the file and hands the printable data over to the linux printing daemon, lpd. lpd is a legacy piece of software for Linux, but it is supported under the modern system used by most Linux distributions, CUPS (the Common Unix Printing System).

You may need to manually install CUPS, and lpr itself, to print this way. If you're operating Debian, or a Debian-derived Linux system like Ubuntu that uses the APT package managements system, you can install them by running the following command:

sudo apt-get update && sudo apt-get install cups cups-client lpr

This command will install the Common Unix Printing System on your system. You should now be able to set up CUPS by directing any web browser to the address: http://localhost:631

Doing so will open a web-based CUPS configuration screen, which should look something like this:

Then, from the command line, add your user to the group lpadmin with the command:

sudo adduserlpadmin

This command will add you to the group of users allowed to administer printers on your system. Now go back to the CUPS web administration panel, and under the administration tab, select "Add Printer." You will be prompted for your username and password, and you should be able to set up a new printer.

lpr [ -E ] [ -H server[:port] ] [ -U username ] [ -P destination[/instance] ] 
    [ -# num-copies [ -h ] [ -l ] [ -m ] [ -o option[=value] ] [ -p] [ -q ] 
    [ -r ] [ -C/J/T title ] [ file(s) ]

Options

lpr myfile.txt

Submits a request to print the file myfile.txt.

cat myfile.txt | lpr

cat a file (myfile.txt), piping the output to lpr, which reads its contents from standard input and sends it to the print daemon for printing.

lpr -#3 myfile.txt

Print 3 copies of myfile.txt.