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rfc:rfc1179

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] 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] 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] 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] 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] 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] 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] 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] 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] 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] 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] 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] 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] 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

McLaughlin [Page 14]

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