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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.
NAME
lp — send files to a printer
SYNOPSIS
lp [-c] [-d dest] [-n copies] [-msw] [-o option]... [-t title] [file...]
DESCRIPTION
The lp utility shall copy the input files to an output destination in an unspecified manner. The default
output destination should be to a hardcopy device, such as a printer or microfilm recorder, that produces
non-volatile, human-readable documents. If such a device is not available to the application, or if the
system provides no such device, the lp utility shall exit with a non-zero exit status.
The actual writing to the output device may occur some time after the lp utility successfully exits.
During the portion of the writing that corresponds to each input file, the implementation shall guarantee
exclusive access to the device.
The lp utility shall associate a unique request ID with each request.
Normally, a banner page is produced to separate and identify each print job. This 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 the -c option 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 the -c option, 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.
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.
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.
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.
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.
EXAMPLES
1. To print file file:
lp -c file
2. To print multiple files with headers:
pr file1 file2 | lp
RATIONALE
The lp utility was designed to be a basic version of a utility that is already available in many
historical implementations. The standard developers considered that it should be implementable simply as:
cat "$@" > /dev/lp
after appropriate processing of options, if that is how the implementation chose to do it and if
exclusive access could be granted (so that two users did not write to the device simultaneously).
Although 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.
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''. Thus, 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).
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.
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.
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.
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.
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.
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.
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.
FUTURE DIRECTIONS
None.
SEE ALSO
mailx
The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment Variables, Section 12.2, Utility
Syntax Guidelines
COPYRIGHT
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 .
IEEE/The Open Group 2017 LP(1POSIX)