LP(1POSIX)

📦 version 2017a, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu resolute, ubuntu stonking

💖 lp(1POSIX) 💖 — from the POSIX Programmer's Manual, but make it make sense

okay so bestie, real talk before we even start: this page is part of the POSIX Programmer's Manual, and the Linux implementation of this interface may differ — like, consult the corresponding Linux manual page for the deets on Linux behavior 💅 — or honestly the interface might not even be implemented on Linux at all. 🙈 Not me warning you first thing, but here we are.

🫶 PROLOG 🫶

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. no cap, read the Linux page if you're on Linux.

✨ NAME ✨

lp — send files to a printer 🖨️💅

🌸 SYNOPSIS 🌸

lp [-c] [-d dest] [-n copies] [-msw] [-o option]... [-t title] [file...]

👑 DESCRIPTION 👑

So the lp utility shall copy the input files to an output destination, and the manner in which it does that is unspecified — iconic, mysterious, we love an enigma. 🦋

The default output destination should be a hardcopy device, like a printer or a microfilm recorder, that produces non-volatile, human-readable documents. If no such device is available to the application — or if the system straight up provides no such device — then lp shall exit with a non-zero exit status. 😭

The actual writing to the output device may occur some time after lp successfully exits. Like, it dips, and then it prints. And during the portion of the writing that corresponds to each input file, the implementation shall guarantee exclusive access to the device. 🔒

lp shall associate a unique request ID with each request. periodt.

Normally, a banner page is produced to separate and identify each print job. That page may be suppressed by implementation-defined conditions, such as an operator command or one of the -o option values. 🎀

💅 OPTIONS 💅

The lp utility shall conform to the Base Definitions volume of POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.

The following options shall be supported:

  • -c — Exit only after further access to any of the input files is no longer required. The application can then safely delete or modify the files without affecting the output operation. Normally, files are not copied, but are linked whenever possible. If -c is not given, then the user should be careful not to remove any of the files before the request has been printed in its entirety. It should also be noted that in the absence of -c, any changes made to the named files after the request is made but before it is printed may be reflected in the printed output. On some implementations, -c may be on by default. 👀
  • -d dest — Specify a string that names the destination (dest). If dest is a printer, the request shall be printed only on that specific printer. If dest is a class of printers, the request shall be printed on the first available printer that is a member of the class. Under certain conditions (printer unavailability, file space limitation, and so on), requests for specific destinations need not be accepted. Destination names vary between systems. 🌈

If -d is not specified, and neither the LPDEST nor PRINTER environment variable is set, an unspecified destination is used. The -d dest option shall take precedence over LPDEST, which in turn shall take precedence over PRINTER. Results are undefined when dest contains a value that is not a valid destination name. 💀

  • -m — Send mail (see mailx) after the files have been printed. By default, no mail is sent upon normal completion of the print request. 📬
  • -n copies — Write copies number of copies of the files, where copies is a positive decimal integer. The methods for producing multiple copies and for arranging the multiple copies when multiple file operands are used are unspecified, except that each file shall be output as an integral whole, not interleaved with portions of other files. 🧚
  • -o option — Specify printer-dependent or class-dependent options. Several such options may be collected by specifying the -o option more than once. ✨
  • -s — Suppress messages from lp. 🤫
  • -t title — Write title on the banner page of the output. 🎀
  • -w — Write a message on the user's terminal after the files have been printed. If the user is not logged in, then mail shall be sent instead. 💌

🦋 OPERANDS 🦋

The following operand shall be supported:

  • file — A pathname of a file to be output. If no file operands are specified, or if a file operand is '-', the standard input shall be used. If a file operand is used, but the -c option is not specified, the process performing the writing to the output device may have user and group permissions that differ from that of the process invoking lp. iykyk — permissions drama.

🍓 STDIN 🍓

The standard input shall be used only if no file operands are specified, or if a file operand is '-'. See the INPUT FILES section. 👀

🌸 INPUT FILES 🌸

The input files shall be text files. that's it, that's the whole section. 💖

🌈 ENVIRONMENT VARIABLES 🌈

The following environment variables shall affect the execution of lp:

  • LANG — Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.1‐2017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)
  • LC_ALL — If set to a non-empty string value, override the values of all the other internationalization variables. 💅
  • LC_CTYPE — Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments and input files).
  • LC_MESSAGES — Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error and informative messages written to standard output. 📢
  • LC_TIME — Determine the format and contents of date and time strings displayed in the lp banner page, if any. 🕰️
  • LPDEST — Determine the destination. If the LPDEST environment variable is not set, the PRINTER environment variable shall be used. The -d dest option takes precedence over LPDEST. Results are undefined when -d is not specified and LPDEST contains a value that is not a valid destination name. 💀
  • NLSPATH — Determine the location of message catalogs for the processing of LC_MESSAGES. 🗂️
  • PRINTER — Determine the output device or destination. If the LPDEST and PRINTER environment variables are not set, an unspecified output device is used. The -d dest option and the LPDEST environment variable shall take precedence over PRINTER. Results are undefined when -d is not specified, LPDEST is unset, and PRINTER contains a value that is not a valid device or destination name. 😭
  • TZ — Determine the timezone used to calculate date and time strings displayed in the lp banner page, if any. If TZ is unset or null, an unspecified default timezone shall be used. 🌍

⚡ ASYNCHRONOUS EVENTS ⚡

Default.

💜 STDOUT 💜

The lp utility shall write a request ID to the standard output, unless -s is specified. The format of the message is unspecified. The request ID can be used on systems supporting the historical cancel and lpstat utilities. 🔥

🙈 STDERR 🙈

The standard error shall be used only for diagnostic messages.

📁 OUTPUT FILES 📁

None. 🎀

🧚 EXTENDED DESCRIPTION 🧚

None. (iconic of her honestly, nothing to explain)

⭐ EXIT STATUS ⭐

The following exit values shall be returned:

  • 0 — All input files were processed successfully. ✨
  • >0 — No output device was available, or an error occurred. 😭

💀 CONSEQUENCES OF ERRORS 💀

Default.

The following sections are informative. 👑 (yes bestie, everything after this is just informative — the vibe is advisory)

🫶 APPLICATION USAGE 🫶

The pr and fold utilities can be used to achieve reasonable formatting for the implementation's default page size. 📄

A conforming application can use one of the file operands only with the -c option, or if the file is publicly readable and guaranteed to be available at the time of printing. This is because POSIX.1‐2008 gives the implementation the freedom to queue up the request for printing at some later time by a different process that might not be able to access the file. 👀 like, it's not being shady, that's just the spec.

🌟 EXAMPLES 🌟

  1. To print file file:
lp -c file
  1. To print multiple files with headers:
pr file1 file2 | lp

💭 RATIONALE 💭

okay so storytime, bestie 🎀 the lp utility was literally designed to be a basic version of a utility that already existed in many historical implementations. The standard developers were like "this could lowkey just be":

cat "$@" > /dev/lp

...after appropriate processing of options, if that's how the implementation chose to do it, and if exclusive access could be granted (so that two users didn't write to the device at the same time). And even though in the future the standard developers may add other options to this utility, it should always be able to execute with no options or operands and send the standard input to an unspecified output device. iconic behavior tbh 💅

This volume of POSIX.1‐2017 makes no representations concerning the format of the printed output, except that it must be human-readable'' and non-volatile''. So bestie, writing by default to a disk or tape drive or a display terminal would not qualify 🚫 (Such destinations are not prohibited when -d dest, LPDEST, or PRINTER are used, however.)

This volume of POSIX.1‐2017 is worded such that a ``print job'' consisting of multiple input files, possibly in multiple copies, is guaranteed to print so that any one file is not intermixed with another, but there is no statement that all the files or copies have to print out together.

The -c option may imply a spooling operation, but this is not required. The utility can be implemented to wait until the printer is ready and then wait until it is finished. Because of that, there is no attempt to define a queuing mechanism (priorities, classes of output, and so on). no queue drama here 💀

On some historical systems, the request ID reported on the STDOUT can be used to later cancel or find the status of a request using utilities not defined in this volume of POSIX.1‐2017. so don't come for us about it 🙈

okay this next bit is genuinely interesting, stay with me 🧚

Although the historical System V lp and BSD lpr utilities have provided similar functionality, they used different names for the environment variable specifying the destination printer. Since the name of the utility here is lp, LPDEST (used by the System V lp utility) was given precedence over PRINTER (used by the BSD lpr utility). Since environments of users frequently contain one or the other environment variable, the lp utility is required to recognize both. If this was not done, many applications would send output to unexpected output devices when users moved from system to system. imagine your printout showing up at the wrong printer, absolute chaos 😭

Some have commented that lp has far too little functionality to make it worthwhile. Requests have proposed additional options or operands or both that added functionality. The requests included:

  • Wording requiring the output to be ``hardcopy''
  • A requirement for multiple printers
  • Options for supporting various page-description languages

Given that a compliant system is not required to even have a printer, placing further restrictions upon the behavior of the printer is not useful. Since hardcopy format is so application-dependent, it is difficult, if not impossible, to select a reasonable subset of functionality that should be required on all compliant systems. fr fr, you can't mandate vibes ✨

The term unspecified is used in this section in lieu of implementation-defined as most known implementations would not be able to make definitive statements in their conformance documents; the existence and usage of printers is very dependent on how the system administrator configures each individual system. main character energy from the sysadmin, honestly 👑

Since the default destination, device type, queuing mechanisms, and acceptable forms of input are all unspecified, usage guidelines for what a conforming application can do are as follows:

  • Use the command in a pipeline, or with -c, so that there are no permission problems and the files can be safely deleted or modified.
  • Limit output to text files of reasonable line lengths and printable characters and include no device-specific formatting information, such as a page description language. The meaning of ``reasonable'' in this context can only be answered as a quality-of-implementation issue, but it should be apparent from historical usage patterns in the industry and the locale. The pr and fold utilities can be used to achieve reasonable formatting for the default page size of the implementation.

Alternatively, the application can arrange its installation in such a way that it requires the system administrator or operator to provide the appropriate information on lp options and environment variable values. delegation, we love to see it 🫶

At a minimum, having this utility in this volume of POSIX.1‐2017 tells the industry that conforming applications require a means to print output and provides at least a command name and LPDEST routing mechanism that can be used for discussions between vendors, application developers, and users. The use of ``should'' in the DESCRIPTION of lp clearly shows the intent of the standard developers, even if they cannot mandate that all systems (such as laptops) have printers. bestie your laptop is valid 💻💖

This volume of POSIX.1‐2017 does not specify what the ownership of the process performing the writing to the output device may be. If -c is not used, it is unspecified whether the process performing the writing to the output device has permission to read file if there are any restrictions in place on who may read file until after it is printed. Also, if -c is not used, the results of deleting file before it is printed are unspecified. so like... don't do that 🙈

🔮 FUTURE DIRECTIONS 🔮

None.

like, genuinely nothing. the future is a void. slay 💅

👀 SEE ALSO 👀

  • mailx

The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines

go read those if you want the full lore, iykyk 📚✨

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

and that's a wrap on the whole page, bestie 🎀 this one came to you from IEEE/The Open Group, dated 2017, filed under LP(1POSIX) — go forth and print responsibly, or at least print something 💖🦋✨

📦 where this page comes from