LP(1P) POSIX Programmer's Manual LP(1P)
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 avail-
able 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.1-2008, 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. Nor-
mally, files are not copied, but are linked whenever possi-
ble. 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 spe-
cific 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. Sev-
eral 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 speci-
fied, 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 vari-
ables that are unset or null. (See the Base Definitions vol-
ume of POSIX.1-2008, Section 8.2, Internationalization Vari-
ables 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 implementa-
tion 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.1-2008 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.1-2008 is worded such that a ``print job'' con-
sisting of multiple input files, possibly in multiple copies, is guar-
anteed 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.1-2008.
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 environ-
ments of users frequently contain one or the other environment vari-
able, 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 diffi-
cult, 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 defini-
tive statements in their conformance documents; the existence and usage
of printers is very dependent on how the system administrator config-
ures 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 modi-
fied.
* 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 val-
ues.
At a minimum, having this utility in this volume of POSIX.1-2008 tells
the industry that conforming applications require a means to print out-
put and provides at least a command name and LPDEST routing mechanism
that can be used for discussions between vendors, application develop-
ers, and users. The use of ``should'' in the DESCRIPTION of lp clearly
shows the intent of the standard developers, even if they cannot man-
date that all systems (such as laptops) have printers.
This volume of POSIX.1-2008 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.1-2008, 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, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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.ker-
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 LP(1P)
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