6: Printing and Managing Print Jobs

Over the years, Linux has had several printing systems, including the venerable Line Printer Daemon (LPD) and LPR Next Generation (LPRng) that are still found in vestigial form on modern Linux distributions. In the past few years, however, most distributions have settled on CUPS (which formerly stood for the Common UNIX Printing System, but has since been shortened to just plain ol’ CUPS) as their backend of choice. CUPS is well supported, easy to use, modern, and a perfect drop-in replacement for LPD and LPRng. The same commands used with LPD and LPRng still work, but now they call functions in CUPS.

This chapter focuses on CUPS because it is the printing system with which most Linux users work. This chapter does not cover how to set up and configure a printer. Most distributions now provide easy-to-use GUI configuration tools to do just that, so you’re going to focus on actually querying and using the printer via the command line.

List All Available Printers

lpstat -p

Before you can begin working with your printers, you need to know what makes up “your printers.” To find the printers configured on your system, use the lpstat command (short for line printer status) along with the -p option.

$ lpstat -p
printer bro is idle. enabled since Jan 01 00:00
printer bro_websanity is idle. enabled since Jan 01 00:00
printer wu_eads14 is idle. enabled since Jan 01 00:00

As you can see, this system has three printers—bro, bro_websanity, and wu_eads14 (bro is short for Brother, the manufacturer of those printers)—and none of them are printing anything at the moment.

Determine Your Default Printer

lpstat -d

You know all of your printers, thanks to running lpstat -p, but which one is the default? As you’re going to see soon, you can send a print job to a specific printer, or you can quickly send it to your default printer. To find out which printer is the default, use the lpstat command with the -d (for default) option.

$ lpstat -d
system default destination: bro

Of course, if you only have one printer connected to your computer, you probably don’t need to run this command. But for laptop users who move around to different locations and who print to different printers, this command is essential.

Find Out How Your Printers Are Connected

lpstat -s

Laptop users find this next command particularly helpful, as it tells them how they access the printers available to them. When you first set up a printer, you must specify how you connect to it. You have several choices:

• Local (parallel, serial, or USB)
• Remote LPD queue
• SMB shared printer (Windows)
• Network printer (TCP)
• Remote CUPS server (IPP/HTTP)
• Network printer with IPP (IPP/HTTP)

To find out what printers are configured for your computer and how you connect to those printers, use lpstat with the -s option.

$ lpstat -s
system default destination: bro
device for bro: socket://192.168.0.160:9100
device for bro_websanity: socket://192.168.1.10:9100
device for wu_eads14: socket://128.252.93.10:9100

In this case, every printer is a network printer, so it uses socket://, followed by the printer’s IP address and its port (9100 is standard for most networked printers, although you might see port 35 used as well). That’s pretty easy, but it can quickly get much more complicated.

Although CUPS is user-friendly in many areas, it’s famously obtuse when it comes to the Uniform Resource Indicators (URIs) used to indicate the locations of printers vis-á-vis your Linux box. Table 6.1 lists each connection method and the type of URI you might see, which should help you understand the list of printers and URIs you see when you run lpstat -s.

Thanks to the rise of network printing in the past several years, it’s getting simpler to connect to printers via socket, ipp, or http. Even so, you’re still going to run into legacy printers that require the older, more complicated connection methods, so it’s good to familiarize yourself with them.

Get All the Information About Your Printers at Once

lpstat -t

Now for the mighty command. The nice thing about using lpstat -p, lpstat -d, or lpstat -s is that you only get the precise bit of information you want. If you want everything all at once, however, use lpstat with the -t option, which dumps everything lpstat knows about your printers onto your shell.

$ lpstat -t
scheduler is running
system default destination: bro
device for bro: socket://192.168.0.160:9100
device for bro_websanity: socket://192.168.1.10:9100
device for wu_eads14: socket://128.252.93.10:9100
bro accepting requests since Jan 01 00:00
bro_websanity accepting requests since Jan 01 00:00
wu_eads14 accepting requests since Jan 01 00:00
printer bro is idle.  enabled since Jan 01 00:00
printer bro_websanity is idle.  enabled since Jan 01 00:00
printer wu_eads14 is idle.  enabled since Jan 01 00:00

You get it all: your default printer, a list of all printers known to your system, the connection methods and locations of those printers, and the status of all printers. The more printers you have configured on your computer, the longer this listing. For some of you, it will be overwhelming, so you might find that lpstat with one of the other options you’ve examined is a better choice.

Print Files to the Default Printer

lpr

Now that you know what printers are on your system, it’s time to actually use them to print something. Printing to your default printer (determined with lpstat -d) is easy.

$ lpr Lovecraft_-_Call_of_Cthulhu.txt

That’s it: Just lpr and the name of the text file. Pretty simple.

Print Files to Any Printer

lpr -P

Printing to the default printer, as shown in the previous section, is pretty easy. If you have more than one printer, however, and you want to print to one that is not the default, simply use the -P option, followed by the name of the printer.

$ lpr -P bro_websanity Lovecraft_-_Call_of_Cthulhu.txt

If you don’t know the names of your printers, use lpstat -p, as discussed previously in the “List All Available Printers” section.

$ lpr -P bro_websanity "Lovecraft - Call of Cthulhu.txt"

$ lpr -P bro_websanity Lovecraft\ -\ Call\ of\ Cthulhu.txt

Print More Than One Copy of a File

lpr -#

If you want to print more than one copy of document, use the -# (the pound sign) option, followed by the number of copies you want:

$ lpr -# 2 -P printer Lovecraft_-_Call_of_Cthulhu.txt

The number can range from 1 to 100. Want more than 100? Repeat the command. Or write a script. Or hire a professional printer!

List Print Jobs

lpq

If you have several jobs queued up to print, you might want to see that list. Perhaps you want to cancel one or more of the jobs (more on how to do that ahead, in the next few sections), you want to find out why a job is taking so long to print, or maybe you just want to know how many print jobs are in line. The lpq command (as in lp queue) lists all jobs currently printing on the default printer.

$ lpq
bro is ready and printing
Rank   Owner Job File(s)                Total Size
active scott 489 Lovecraft_-_Call_of_C 108544 bytes

If you want to find out the status of print queues for all your printers, not just your default, simply append -a (as in all) after lpq:

$ lpq -a
Rank   Owner Job File(s)                Total Size
active scott 489 Lovecraft_-_Call_of_C 108544 bytes
1st    scott 490 ERB_-_A Princess_of_M 524288 bytes

Keep in mind two things. First, the listing provided by lpq -a is cut off, so while the filenames are actually Lovecraft_-_Call_of_Cthulhu.txt and ERB_-_A Princess_of_Mars.txt, you don’t see the entire name because lpq only shows a certain number of characters.

Second, and this is very important, lpq is not showing all the print jobs the printer knows about, only those that your machine knows about. From the printer’s perspective, the print queue might actually look like this:

• Lovecraft_-_Call_of_Cthulhu.txt
• Doyle_-_The_Lost_World.txt
• ERB_-_A Princess_of_Mars.txt

To find out the actual queue on the printer, you have to use whatever management utilities come with that device, which is far beyond the scope of this book.

List Print Jobs by Printer

lpstat

The lpq command shows you the files that are queued to print, but it doesn’t tell you to which printer the files are being sent. To learn that, you need to use the lpstat command, covered earlier in “List All Available Printers.” This time, however, simply use lpstat without any options at all:

$ lpstat
bro-489           rsgranne  108544  Tue 10 Dec 2005 03:00:09 PM CST
bro_websanity-490 rsgranne  524288  Tue 10 Dec 2005 03:05:05 PM CST

The result is a list of print jobs, with the name of each printer handling the job at the beginning of each line. Did you accidentally send a job to a printer to which you’re not currently connected? Find out with lpstat and then delete the job, which you’ll learn in the next section.

Cancel the Current Print Job Sent to the Default Printer

lprm

Do you want to cancel the current print job being sent to your default printer? Just use lprm (as in lp remove):

$ lprm

Be sure to issue this command with haste. Many printers now are so fast and have so much memory that the job might have already left your machine and be running on the printer. In that case, find the Cancel button on your printer and press it quickly!

Cancel a Print Job Sent to Any Printer

lprm job ID

In the previous section, you learned how to cancel the current print job going to the default printer. But what if the job is queued and won’t start for another few minutes? Or what if the job is heading for a printer that’s not the default? In those cases, you want to still use lprm, but you want to tell the command which job to cancel by referencing the job’s ID number.

Look back at the examples in “List Print Jobs.” The third column is labeled “Job” and has a number in it. Now look back at “List Print Jobs by Printer.” After the name of each printer is a hyphen and then a number—the same number seen in “List Print Jobs.” That number is the job ID number. Specify that number to lprm, and that exact job will be removed.

$ lpstat
bro-489           rsgranne  108544  Tue 10 Dec 2005 03:00:09 PM CST
bro_websanity-490 rsgranne  524288  Tue 10 Dec 2005 03:05:05 PM CST
$ lprm 490
$ lpstat
bro-489           rsgranne  108544  Tue 10 Dec 2005 03:00:09 PM CST

You can really save yourself from a needless waste of paper, toner, and ink using this particular command. Next time you realize that you just sent a 500-page document full of large pictures to your printer and stop it using lprm and a job ID number, send an email my way and thank me.

Cancel All Print Jobs

lprm -

What if you have several print jobs you want to cancel? You could delete them all by specifying all of their job ID numbers, like this:

$ lprm 489 490 491 492 493

That’s too much typing, however. If you want to get rid of all print jobs you’ve queued on every printer, just follow lprm with a hyphen:

$ lprm -

It’s quick, it’s painless, and it’s lazy in the best Linux tradition. Nothing to be ashamed of there!

Conclusion

Printing is a central activity people perform on their computers, so it’s important to learn how to print effectively. Part of printing is knowing how to query printers and jobs as well as send those jobs to printers in the first place. Of course, not all jobs need to be printed, so it’s important to know how to cancel unnecessary jobs as well. This chapter covers the major tasks you’ll need to work with your printers from within Linux, but let me leave you with a final bit of advice: Automatic duplex printers that work with Linux have now fallen in price drastically, and they’ll help you save a small fortune in paper. Check one out when you’re next in the market for a printer. You’ll be glad you did.