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+Network Printing Working Group L. McLaughlin III, Editor
+Request for Comments: 1179 The Wollongong Group
+ August 1990
+
+
+ Line Printer Daemon Protocol
+
+Status of this Memo
+
+ This RFC describes an existing print server protocol widely used on
+ the Internet for communicating between line printer daemons (both
+ clients and servers). This memo is for informational purposes only,
+ and does not specify an Internet standard. Please refer to the
+ current edition of the "IAB Official Protocol Standards" for the
+ standardization state and status of this protocol. Distribution of
+ this memo is unlimited.
+
+1. Introduction
+
+ The Berkeley versions of the Unix(tm) operating system provide line
+ printer spooling with a collection of programs: lpr (assign to
+ queue), lpq (display the queue), lprm (remove from queue), and lpc
+ (control the queue). These programs interact with an autonomous
+ process called the line printer daemon. This RFC describes the
+ protocols with which a line printer daemon client may control
+ printing.
+
+ This memo is based almost entirely on the work of Robert Knight at
+ Princeton University. I gratefully acknowledge his efforts in
+ deciphering the UNIX lpr protocol and producing earlier versions of
+ this document.
+
+2. Model of Printing Environment
+
+ A group of hosts request services from a line printer daemon process
+ running on a host. The services provided by the process are related
+ to printing jobs. A printing job produces output from one file.
+ Each job will have a unique job number which is between 0 and 999,
+ inclusive. The jobs are requested by users which have names. These
+ user names may not start with a digit.
+
+3. Specification of the Protocol
+
+ The specification includes file formats for the control and data
+ files as well as messages used by the protocol.
+
+
+
+
+
+
+McLaughlin [Page 1]
+\f
+RFC 1179 LPR August 1990
+
+
+3.1 Message formats
+
+ LPR is a a TCP-based protocol. The port on which a line printer
+ daemon listens is 515. The source port must be in the range 721 to
+ 731, inclusive. A line printer daemon responds to commands send to
+ its port. All commands begin with a single octet code, which is a
+ binary number which represents the requested function. The code is
+ immediately followed by the ASCII name of the printer queue name on
+ which the function is to be performed. If there are other operands
+ to the command, they are separated from the printer queue name with
+ white space (ASCII space, horizontal tab, vertical tab, and form
+ feed). The end of the command is indicated with an ASCII line feed
+ character.
+
+4. Diagram Conventions
+
+ The diagrams in the rest of this RFC use these conventions. These
+ diagrams show the format of an octet stream sent to the server. The
+ outermost box represents this stream. Each box within the outermost
+ one shows one portion of the stream. If the contents of the box is
+ two decimal digits, this indicates that the binary 8 bit value is to
+ be used. If the contents is two uppercase letters, this indicates
+ that the corresponding ASCII control character is to be used. An
+ exception to this is that the character SP can be interpreted as
+ white space. (See the preceding section for a definition.) If the
+ contents is a single letter, the ASCII code for this letter must be
+ sent. Otherwise, the contents are intended to be mnemonic of the
+ contents of the field which is a sequence of octets.
+
+5. Daemon commands
+
+ The verbs in the command names should be interpreted as statements
+ made to the daemon. Thus, the command "Print any waiting jobs" is an
+ imperative to the line printer daemon to which it is sent. A new
+ connection must be made for each command to be given to the daemon.
+
+5.1 01 - Print any waiting jobs
+
+ +----+-------+----+
+ | 01 | Queue | LF |
+ +----+-------+----+
+ Command code - 1
+ Operand - Printer queue name
+
+ This command starts the printing process if it not already running.
+
+
+
+
+
+
+McLaughlin [Page 2]
+\f
+RFC 1179 LPR August 1990
+
+
+5.2 02 - Receive a printer job
+
+ +----+-------+----+
+ | 02 | Queue | LF |
+ +----+-------+----+
+ Command code - 2
+ Operand - Printer queue name
+
+ Receiving a job is controlled by a second level of commands. The
+ daemon is given commands by sending them over the same connection.
+ The commands are described in the next section (6).
+
+ After this command is sent, the client must read an acknowledgement
+ octet from the daemon. A positive acknowledgement is an octet of
+ zero bits. A negative acknowledgement is an octet of any other
+ pattern.
+
+5.3 03 - Send queue state (short)
+
+ +----+-------+----+------+----+
+ | 03 | Queue | SP | List | LF |
+ +----+-------+----+------+----+
+ Command code - 3
+ Operand 1 - Printer queue name
+ Other operands - User names or job numbers
+
+ If the user names or job numbers or both are supplied then only those
+ jobs for those users or with those numbers will be sent.
+
+ The response is an ASCII stream which describes the printer queue.
+ The stream continues until the connection closes. Ends of lines are
+ indicated with ASCII LF control characters. The lines may also
+ contain ASCII HT control characters.
+
+5.4 04 - Send queue state (long)
+
+ +----+-------+----+------+----+
+ | 04 | Queue | SP | List | LF |
+ +----+-------+----+------+----+
+ Command code - 4
+ Operand 1 - Printer queue name
+ Other operands - User names or job numbers
+
+ If the user names or job numbers or both are supplied then only those
+ jobs for those users or with those numbers will be sent.
+
+ The response is an ASCII stream which describes the printer queue.
+ The stream continues until the connection closes. Ends of lines are
+
+
+
+McLaughlin [Page 3]
+\f
+RFC 1179 LPR August 1990
+
+
+ indicated with ASCII LF control characters. The lines may also
+ contain ASCII HT control characters.
+
+5.5 05 - Remove jobs
+
+ +----+-------+----+-------+----+------+----+
+ | 05 | Queue | SP | Agent | SP | List | LF |
+ +----+-------+----+-------+----+------+----+
+ Command code - 5
+ Operand 1 - Printer queue name
+ Operand 2 - User name making request (the agent)
+ Other operands - User names or job numbers
+
+ This command deletes the print jobs from the specified queue which
+ are listed as the other operands. If only the agent is given, the
+ command is to delete the currently active job. Unless the agent is
+ "root", it is not possible to delete a job which is not owned by the
+ user. This is also the case for specifying user names instead of
+ numbers. That is, agent "root" can delete jobs by user name but no
+ other agents can.
+
+6. Receive job subcommands
+
+ These commands are processed when the line printer daemon has
+ been given the receive job command. The daemon will continue to
+ process commands until the connection is closed.
+
+ After a subcommand is sent, the client must wait for an
+ acknowledgement from the daemon. A positive acknowledgement is an
+ octet of zero bits. A negative acknowledgement is an octet of any
+ other pattern.
+
+ LPR clients SHOULD be able to sent the receive data file and receive
+ control file subcommands in either order. LPR servers MUST be able
+ to receive the control file subcommand first and SHOULD be able to
+ receive the data file subcommand first.
+
+6.1 01 - Abort job
+
+ Command code - 1
+ +----+----+
+ | 01 | LF |
+ +----+----+
+
+ No operands should be supplied. This subcommand will remove any
+ files which have been created during this "Receive job" command.
+
+
+
+
+
+McLaughlin [Page 4]
+\f
+RFC 1179 LPR August 1990
+
+
+6.2 02 - Receive control file
+
+ +----+-------+----+------+----+
+ | 02 | Count | SP | Name | LF |
+ +----+-------+----+------+----+
+ Command code - 2
+ Operand 1 - Number of bytes in control file
+ Operand 2 - Name of control file
+
+ The control file must be an ASCII stream with the ends of lines
+ indicated by ASCII LF. The total number of bytes in the stream is
+ sent as the first operand. The name of the control file is sent as
+ the second. It should start with ASCII "cfA", followed by a three
+ digit job number, followed by the host name which has constructed the
+ control file. Acknowledgement processing must occur as usual after
+ the command is sent.
+
+ The next "Operand 1" octets over the same TCP connection are the
+ intended contents of the control file. Once all of the contents have
+ been delivered, an octet of zero bits is sent as an indication that
+ the file being sent is complete. A second level of acknowledgement
+ processing must occur at this point.
+
+6.3 03 - Receive data file
+
+ +----+-------+----+------+----+
+ | 03 | Count | SP | Name | LF |
+ +----+-------+----+------+----+
+ Command code - 3
+ Operand 1 - Number of bytes in data file
+ Operand 2 - Name of data file
+
+ The data file may contain any 8 bit values at all. The total number
+ of bytes in the stream may be sent as the first operand, otherwise
+ the field should be cleared to 0. The name of the data file should
+ start with ASCII "dfA". This should be followed by a three digit job
+ number. The job number should be followed by the host name which has
+ constructed the data file. Interpretation of the contents of the
+ data file is determined by the contents of the corresponding control
+ file. If a data file length has been specified, the next "Operand 1"
+ octets over the same TCP connection are the intended contents of the
+ data file. In this case, once all of the contents have been
+ delivered, an octet of zero bits is sent as an indication that the
+ file being sent is complete. A second level of acknowledgement
+ processing must occur at this point.
+
+
+
+
+
+
+McLaughlin [Page 5]
+\f
+RFC 1179 LPR August 1990
+
+
+7. Control file lines
+
+ This section discusses the format of the lines in the control file
+ which is sent to the line printer daemon.
+
+ Each line of the control file consists of a single, printable ASCII
+ character which represents a function to be performed when the file
+ is printed. Interpretation of these command characters are case-
+ sensitive. The rest of the line after the command character is the
+ command's operand. No leading white space is permitted after the
+ command character. The line ends with an ASCII new line.
+
+ Those commands which have a lower case letter as a command code are
+ used to specify an actual printing request. The commands which use
+ upper case are used to describe parametric values or background
+ conditions.
+
+ Some commands must be included in every control file. These are 'H'
+ (responsible host) and 'P' (responsible user). Additionally, there
+ must be at least one lower case command to produce any output.
+
+7.1 C - Class for banner page
+
+ +---+-------+----+
+ | C | Class | LF |
+ +---+-------+----+
+ Command code - 'C'
+ Operand - Name of class for banner pages
+
+ This command sets the class name to be printed on the banner page.
+ The name must be 31 or fewer octets. The name can be omitted. If it
+ is, the name of the host on which the file is printed will be used.
+ The class is conventionally used to display the host from which the
+ printing job originated. It will be ignored unless the print banner
+ command ('L') is also used.
+
+7.2 H - Host name
+
+ +---+------+----+
+ | H | Host | LF |
+ +---+------+----+
+ Command code - 'H'
+ Operand - Name of host
+
+ This command specifies the name of the host which is to be treated as
+ the source of the print job. The command must be included in the
+ control file. The name of the host must be 31 or fewer octets.
+
+
+
+
+McLaughlin [Page 6]
+\f
+RFC 1179 LPR August 1990
+
+
+7.3 I - Indent Printing
+
+ +---+-------+----+
+ | I | count | LF |
+ +---+-------+----+
+ Command code - 'I'
+ Operand - Indenting count
+
+ This command specifies that, for files which are printed with the
+ 'f', of columns given. (It is ignored for other output generating
+ commands.) The identing count operand must be all decimal digits.
+
+7.4 J - Job name for banner page
+
+ +---+----------+----+
+ | J | Job name | LF |
+ +---+----------+----+
+ Command code - 'J'
+ Operand - Job name
+
+ This command sets the job name to be printed on the banner page. The
+ name of the job must be 99 or fewer octets. It can be omitted. The
+ job name is conventionally used to display the name of the file or
+ files which were "printed". It will be ignored unless the print
+ banner command ('L') is also used.
+
+7.5 L - Print banner page
+
+ +---+------+----+
+ | L | User | LF |
+ +---+------+----+
+ Command code - 'L'
+ Operand - Name of user for burst pages
+
+ This command causes the banner page to be printed. The user name can
+ be omitted. The class name for banner page and job name for banner
+ page commands must precede this command in the control file to be
+ effective.
+
+7.6 M - Mail When Printed
+
+ +---+------+----+
+ | M | user | LF |
+ +---+------+----+
+ Command code - 'M'
+ Operand - User name
+
+ This entry causes mail to be sent to the user given as the operand at
+
+
+
+McLaughlin [Page 7]
+\f
+RFC 1179 LPR August 1990
+
+
+ the host specified by the 'H' entry when the printing operation ends
+ (successfully or unsuccessfully).
+
+7.7 N - Name of source file
+
+ +---+------+----+
+ | N | Name | LF |
+ +---+------+----+
+ Command code - 'N'
+ Operand - File name
+
+ This command specifies the name of the file from which the data file
+ was constructed. It is returned on a query and used in printing with
+ the 'p' command when no title has been given. It must be 131 or
+ fewer octets.
+
+7.8 P - User identification
+
+ +---+------+----+
+ | P | Name | LF |
+ +---+------+----+
+ Command code - 'P'
+ Operand - User id
+
+ This command specifies the user identification of the entity
+ requesting the printing job. This command must be included in the
+ control file. The user identification must be 31 or fewer octets.
+
+7.9 S - Symbolic link data
+
+ +---+--------+----+-------+----+
+ | S | device | SP | inode | LF |
+ +---+--------+----+-------+----+
+ Command code - 'S'
+ Operand 1 - Device number
+ Operand 2 - Inode number
+
+ This command is used to record symbolic link data on a Unix system so
+ that changing a file's directory entry after a file is printed will
+ not print the new file. It is ignored if the data file is not
+ symbolically linked.
+
+
+
+
+
+
+
+
+
+
+McLaughlin [Page 8]
+\f
+RFC 1179 LPR August 1990
+
+
+7.10 T - Title for pr
+
+ +---+-------+----+
+ | T | title | LF |
+ +---+-------+----+
+ Command code - 'T'
+ Operand - Title text
+
+ This command provides a title for a file which is to be printed with
+ either the 'p' command. (It is ignored by all of the other printing
+ commands.) The title must be 79 or fewer octets.
+
+7.11 U - Unlink data file
+
+ +---+------+----+
+ | U | file | LF |
+ +---+------+----+
+ Command code - 'U'
+ Operand - File to unlink
+
+ This command indicates that the specified file is no longer needed.
+ This should only be used for data files.
+
+7.12 W - Width of output
+
+ +---+-------+----+
+ | W | width | LF |
+ +---+-------+----+
+ Command code - 'W'
+ Operand - Width count
+
+ This command limits the output to the specified number of columns for
+ the 'f', 'l', and 'p' commands. (It is ignored for other output
+ generating commands.) The width count operand must be all decimal
+ digits. It may be silently reduced to some lower value. The default
+ value for the width is 132.
+
+7.13 1 - troff R font
+
+ +---+------+----+
+ | 1 | file | LF |
+ +---+------+----+
+ Command code - '1'
+ Operand - File name
+
+ This command specifies the file name for the troff R font. [1] This
+ is the font which is printed using Times Roman by default.
+
+
+
+
+McLaughlin [Page 9]
+\f
+RFC 1179 LPR August 1990
+
+
+7.14 2 - troff I font
+
+ +---+------+----+
+ | 2 | file | LF |
+ +---+------+----+
+ Command code - '2'
+ Operand - File name
+
+ This command specifies the file name for the troff I font. [1] This
+ is the font which is printed using Times Italic by default.
+
+7.15 3 - troff B font
+
+ +---+------+----+
+ | 3 | file | LF |
+ +---+------+----+
+ Command code - '3'
+ Operand - File name
+
+ This command specifies the file name for the troff B font. [1] This
+ is the font which is printed using Times Bold by default.
+
+7.16 4 - troff S font
+
+ +---+------+----+
+ | 4 | file | LF |
+ +---+------+----+
+ Command code - '4'
+ Operand - File name
+
+ This command specifies the file name for the troff S font. [1] This
+ is the font which is printed using Special Mathematical Font by
+ default.
+
+7.17 c - Plot CIF file
+
+ +---+------+----+
+ | c | file | LF |
+ +---+------+----+
+ Command code - 'c'
+ Operand - File to plot
+
+ This command causes the data file to be plotted, treating the data as
+ CIF (CalTech Intermediate Form) graphics language. [2]
+
+
+
+
+
+
+
+McLaughlin [Page 10]
+\f
+RFC 1179 LPR August 1990
+
+
+7.18 d - Print DVI file
+
+ +---+------+----+
+ | d | file | LF |
+ +---+------+----+
+ Command code - 'd'
+ Operand - File to print
+
+ This command causes the data file to be printed, treating the data as
+ DVI (TeX output). [3]
+
+7.19 f - Print formatted file
+
+ +---+------+----+
+ | f | file | LF |
+ +---+------+----+
+ Command code - 'f'
+ Operand - File to print
+
+ This command cause the data file to be printed as a plain text file,
+ providing page breaks as necessary. Any ASCII control characters
+ which are not in the following list are discarded: HT, CR, FF, LF,
+ and BS.
+
+7.20 g - Plot file
+
+ +---+------+----+
+ | g | file | LF |
+ +---+------+----+
+ Command code - 'g'
+ Operand - File to plot
+
+ This command causes the data file to be plotted, treating the data as
+ output from the Berkeley Unix plot library. [1]
+
+7.21 k - Reserved for use by Kerberized LPR clients and servers.
+
+7.22 l - Print file leaving control characters
+
+ +---+------+----+
+ | l | file | LF |
+ +---+------+----+
+ Command code - 'l' (lower case L)
+ Operand - File to print
+
+ This command causes the specified data file to printed without
+ filtering the control characters (as is done with the 'f' command).
+
+
+
+
+McLaughlin [Page 11]
+\f
+RFC 1179 LPR August 1990
+
+
+7.23 n - Print ditroff output file
+
+ +---+------+----+
+ | n | file | LF |
+ +---+------+----+
+ Command code - 'n'
+ Operand - File to print
+
+ This command prints the data file to be printed, treating the data as
+ ditroff output. [4]
+
+7.24 o - Print Postscript output file
+
+ +---+------+----+
+ | o | file | LF |
+ +---+------+----+
+ Command code - 'o'
+ Operand - File to print
+
+ This command prints the data file to be printed, treating the data as
+ standard Postscript input.
+
+7.25 p - Print file with 'pr' format
+
+ +---+------+----+
+ | p | file | LF |
+ +---+------+----+
+ Command code - 'p'
+ Operand - File to print
+
+ This command causes the data file to be printed with a heading, page
+ numbers, and pagination. The heading should include the date and
+ time that printing was started, the title, and a page number
+ identifier followed by the page number. The title is the name of
+ file as specified by the 'N' command, unless the 'T' command (title)
+ has been given. After a page of text has been printed, a new page is
+ started with a new page number. (There is no way to specify the
+ length of the page.)
+
+7.26 r - File to print with FORTRAN carriage control
+
+ +---+------+----+
+ | r | file | LF |
+ +---+------+----+
+ Command code - 'r'
+ Operand - File to print
+
+ This command causes the data file to be printed, interpreting the
+
+
+
+McLaughlin [Page 12]
+\f
+RFC 1179 LPR August 1990
+
+
+ first column of each line as FORTRAN carriage control. The FORTRAN
+ standard limits this to blank, "1", "0", and "+" carriage controls.
+ Most FORTRAN programmers also expect "-" (triple space) to work as
+ well.
+
+7.27 t - Print troff output file
+
+ +---+------+----+
+ | t | file | LF |
+ +---+------+----+
+ Command code - 't'
+ Operand - File to print
+
+ This command prints the data file as Graphic Systems C/A/T
+ phototypesetter input. [5] This is the standard output of the Unix
+ "troff" command.
+
+7.28 v - Print raster file
+
+ +---+------+----+
+ | v | file | LF |
+ +---+------+----+
+ Command code - 'v'
+ Operand - File to print
+
+ This command prints a Sun raster format file. [6]
+
+7.29 z - Reserved for future use with the Palladium print system.
+
+REFERENCES and BIBLIOGRAPHY
+
+ [1] Computer Science Research Group, "UNIX Programmer's Reference
+ Manual", USENIX, 1986.
+
+ [2] Hon and Sequin, "A Guide to LSI Implementation", XEROX PARC,
+ 1980.
+
+ [3] Knuth, D., "TeX The Program".
+
+ [4] Kernighan, B., "A Typesetter-independent TROFF".
+
+ [5] "Model C/A/T Phototypesetter", Graphic Systems, Inc. Hudson, N.H.
+
+ [6] Sun Microsystems, "Pixrect Reference Manual", Sun Microsystems,
+ Mountain View, CA, 1988.
+
+
+
+
+
+
+McLaughlin [Page 13]
+\f
+RFC 1179 LPR August 1990
+
+
+Security Considerations
+
+ Security issues are not discussed in this memo.
+
+Author's Address
+
+ Leo J. McLaughlin III
+ The Wollongong Group
+ 1129 San Antonio Road
+ Palo Alto, CA 94303
+
+ Phone: 415-962-7100
+
+ EMail: ljm@twg.com
+
+
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+McLaughlin [Page 14]
+\f
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