отправлять файлы на принтер (send files to a printer)
Пролог (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.
Имя (Name)
lp — send files to a printer
Синопсис (Synopsis)
lp [-c] [-d dest] [-n copies] [-msw] [-o option]... [-t title] [file...]
Описание (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.
Параметры (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(1p)) 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.
Операнды (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.
Стандартный ввод (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.
Входные файлы (Input files)
The input files shall be text files.
Переменные окружения (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.
Асинхронные события (Asynchronous events)
Default.
Стандартный вывод (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.
Стандартный вывод сообщений (Stderr)
The standard error shall be used only for diagnostic messages.
Выходные файлы (Output files)
None.
Расширенное описание (Extended description)
None.
Статус выхода (Exit)
The following exit values shall be returned:
0 All input files were processed successfully.
>0 No output device was available, or an error occurred.
Последствия ошибок (Consequences of errors)
Default.
The following sections are informative.
Использование в приложениях (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.
Примеры (Examples)
1. To print file file:
lp -c file
2. To print multiple files with headers:
pr file1 file2 | lp
Обоснование (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.
Будущие направления (Future directions)
None.
Смотри также (See also)
mailx(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
