1.1. Copyright and Disclaimer

Material included in this document from the ifhp distribution Copyright Patrick Powell 1988-1999, where applicable. The rights to distribute this document complete or in part are hereby granted for non-commercial purposes. Partial reproductions must acknowledge the source. Permission to distribute this file together with LPRng, ifhp and `derived works' is explicitly granted.

THE MATERIAL IN THIS HOWTO IS PROVIDED WITHOUT FEE AND AS-IS WITH NO WARRANTY REGARDING FITNESS OF USE FOR ANY PURPOSE. THE AUTHOR AND ALL CONTRIBUTORS ARE NOT LIABLE FOR ANY DAMAGES, DIRECT OR INDIRECT, RESULTING FROM THE USE OF INFORMATION PROVIDED IN THIS DOCUMENT.

1.2. Commercial Support

AStArt Technologies (http://www.astart.com) provides commercial support and enhancements for LPRng, ifhp, and other network software. AStArt provides network and system consulting services for UNIX and NT systems, as well as real time and network software.

1.3. Web Site

Web Page: http://www.astart.com/LPRng.html

1.4. FTP Sites

Main FTP Site:

Mirrors:

1.5. Mailing List

To join the LPRng mailing list, please send mail to lprng-request@lprng.ie with the only the word subscribe in the body of the message.

1.6. PGP Public Key

The LPRng and ifhp distributions have MD5 checksum files which are signed with a PGP public key. Here is the key for validating the checksums:

    Type Bits/KeyID    Date       User ID
    pub  1024/00D95C9D 1997/01/31 Patrick A. Powell <papowell@astart.com>
                                  Patrick A. Powell <papowell@sdsu.edu>
    
    -----BEGIN PGP PUBLIC KEY BLOCK-----
    Version: 2.6.3i
    
    mQCNAzLygTQAAAEEANBW5fPYjN3wSAnP9xWOUc3CvsMUxjip0cN2sY5qrdoJyIhn
    qbAspBopR+tGQfyp5T7C21yfWRRnfXmoJ3FVtgToAsJUYmzoSFY08eDx+rmSqCLe
    rdJjX8aG8jVXpGipEo9U4QsUK+OKzx3/y/OaK4cizoWqKvy1l4lEzDsA2VydAAUT
    tCdQYXRyaWNrIEEuIFBvd2VsbCA8cGFwb3dlbGxAYXN0YXJ0LmNvbT6JAJUDBRA0
    XonoiUTMOwDZXJ0BAQ2cBAC7zU9Fn3sC3x0USJ+3vjhg/qA+Gjb5Fi1dJd4solc4
    vJvtf0UL/1/rGipbR+A0XHpHzJUMP9ZfJzKZjaK/d0ZBNlS3i+JnypypeQiAqo9t
    FV0OyUCwDfWybgAORuAa2V6UJnAhvj/7TpxMmCApolaIb4yFyKunHa8aBxN+17Ro
    rrQlUGF0cmljayBBLiBQb3dlbGwgPHBhcG93ZWxsQHNkc3UuZWR1PokAlQMFEDLy
    gTSJRMw7ANlcnQEBYBYD/0zTeoiDNnI+NjaIei6+6z6oakqO70qFVx0FG3aP3kRH
    WlDhdtFaAuaMRh+RItHfFfcHhw5K7jiJdgKiTgGfj5Vt3OdHYkeeh/sddqgf9YnS
    tpj0u5NfrotPTUw39n6YTgS5/aW0PQfO9dx7jVUcGeod1TGXTe9mIhDMwDJI4J14
    =3Zbp
    -----END PGP PUBLIC KEY BLOCK-----

2.1. Additional Recommended Software

The following software is recommended for use with ifhp. If your printer does not support PostScript, PCL, or text printing directly you will need to install GhostScript to convert from PostScript to the printer format and use a suitable text to PostScript converter.

2.2. Installation

The installation procedure uses the configure facility to generate Makefiles. By convention, these files have the following variables that install the ifhp executables and configuration files in the following locations:

The following files are installed as shown below:

The configuration you choose should match that of the LPRng print spooler. For example:

    ./configure --prefix=/usr --sysconfdir=/etc \
      --mandir=/usr/share/man
    
    executables and files in
       /usr/libexec/filters         ifhp
       /etc                         ifhp.conf
       /usr/share/man/man[0-9]      ifhp.man1

First, we untar, configure, compile, and install the software:

    h4: {1} % gunzip -c ifhp-<version>.tgz | tar xvf -
    h4: {2} % cd ifhp-<version>
    h4: {3} % ./configure  [ ... configuration options ]
    h4: {4} % make clean all
    h4: {5} % su   # you must do the following commands as root
    h4: {6} # make install

Modify your printcap file to use ifhp. Your printcap usually has the following format; older version of lpd require :\ at the end of each line of a printcap entry. The :if and :of filter entries are usually the ones of interest.

    lp:
      :lp=xxxx:sd=xxxx:....
      :if=/usr/local/path_to_old_filters/old_if_filter
      :of=/usr/local/path_to_old_filters/old_of_filter

Your new printcap entry will look like the one below. The MODEL information is described in the next section.

    lp:
      :lp=xxxx:sd=xxxx:....
      #  see text for details about the next line
      :ifhp=model=MODEL,status@
      :filter=/usr/local/libexec/filters/ifhp
      # only if you are using accounting or banners
      #:of=/usr/local/libexec/filters/ifhp

Select a suitable printer from the entries in the configuration file (/usr/local/etc/lpd.conf or /etc/lpd.conf). These are described in more detail in the next section.

Shut down and restart your print spooler and then send a job to the printer. If this works and you do not need any further capabilities of ifhp such as error reporting or printer monitoring, then you are finished.

If you want to use additional capabilities, then you should read the detailed instructions in the next couple of sections.

2.3. Printer Models Supported

There are over 500 different printer models, types and configurations supported by ifhp. If your printer is not currently supported and you have documentation about the printer then send mail to the LPRng Mailing List and support will be added.

The default printer is an HP LaserJet 4MP, which supports PostScript Level 3, PCL5, PJL, and has bidirectional communication and a functional pagecounter.

The ifhp.conf configuration file contains configuration entries for various models of printers. Each entry has a name usually corresponding to the model of printer or its basic capabilities. For example, the HP LaserJet 4 printer has the model=hp4 configuration entry. The default printer configuration covers a wide range of network printers manufactured by Hewlett-Packard, Canon, Epson, and others and is for a printer that has a bidirectional communications connection that allows it to report status information and the following capabilities:

1. PJL support (pjl) compatible with HP 4 family of printers

2. PostScript (PS) support (ps).

3. PCL support (pcl).

4. Text files printed as PCL (text, default_language=pcl).

There is also support for PostScript only printers (model=ps), Tektronics Phasers (model=phaser), QMS (model=qmsXXX) and others. The best way to determine the printers currently supported is to examine the ifhp.conf file. The following is a sample of the various entries in the configuration file.

If your printer is not in this this list then you can use the following guidelines. If you have a PostScript only printer you should use the ps model. If you have a PCL only printer, then pcl is recommended. If you want to process PostScript files on your PCL only printer then install GhostScript and use pcl_ps entry and select the GhostScript driver suitable for your printer.

The other model entries are used when specific printer functionality or features are needed. For example, if you want to do accounting or use landscape mode, then you should check for your specific printer model in the configuration file.

3.1. Input Tray Selection

If a printer supports an input tray selection mechanism, then the following options are recommended for use. Local conditions or printer type may require addition options.

3.2. Output Bin Selection

If a printer has an output bin selection mechanism or some other finishing mechanism, then the following are recommended for use.

3.3. Media Size (Paper) Selection

The paper size selection facilities usually are quite printer dependent, and the input tray selection and paper size selection mechanisms may interact in strange and mysterious ways.

3.4. Media Type Selection

Media Type is not the same as paper size, and corresponds to the name assigned to a particular media. Of course, the issue is complicated by the fact that some media have standard sizes as well. Again, the input tray selection, media size, and media type selection will interact in confusing and mysterious ways, depending on the whim of the printer firmware implementors.

You will also notice that there is no general mediatype=name selection mechanism. This is due to the extremely different way that the media names must be passed for PostScript, PJL, and PCL.

3.5. Duplex and Simplex

Duplex printing is when impressions are placed on both sides of a sheet of media. Due to a general lack of conventions, the orientation of each of the impressions varies from vendor to vendor, and has changed over the years.

3.6. Copies

This option has been provided to effectively allow the printer to make multiple copies of a single page or job. This option tends to be misimplemented on almost all known printers, and it is strongly recommended that users do not use it. However, for completeness, compatibility, and implementor consideration, this is included, even against the better judgement of the implementors of the ifhp software.

4.1. Printer Configurations

A printer consists of a hardware print engine which marks the output page and delivers it, a set of control hardware that takes a print job in a well defined format and operates the hardware to produce output according to information in the print job, and a communication channel from the computer to the control hardware. The control hardware is sometimes called a print engine. In most modern computers the control hardware may consist of multiple microprocessors, each with their own firmware, and each performing a specific printing task. For example, one may control the paper feed path, one may do rasterization, and one may handle communications with the outside world.

In order to set up printing correctly, it is necessary to know the following information about your printer.

1. The capabilities of the hardware. This is dependent on the model of printer, and may be such things as the page feed, output and input tray selection, numbers of columns and/or rows of output available on the output device. This information is readily available from most manufacturers.

2. The print job language recognized by the control hardware. This is the special set of codes, commands, and formats recognized by the control hardware.

3. The protocol used to send jobs to the printer and obtain status about the printing activity.

Usually the capabilities of a modern printer are very well known and documented, and the ifhp filter and most print spooling software has little difficulty working with them.

The following checklist will help you in setting up your printer. The various options that you will need to know about are indicated where appropriate.

1. Printer Model (model=???) What is the exact printer model? Check the serial number or other identification to get this information. You should check the ifhp.conf configuration file to see if your printer is already supported.

2. Print Languages Supported By Your Printer

   1. PJL? (pjl or pjl@) The Printer Job Language (PJL) is a high level language supported by many Hewlett-Packard printers that allows some print system configuration to be performed. Due to historical developments, not all printers support all PJL language facilities, and some support them in different ways than other printers. The ifhp filter can use the PJL support for a printer if it is available.

   2. PostScript (and what version)? (ps or ps@) PostScript is the most common print job language in use. If your printer supports PostScript, then you will have a relatively trouble free time with it. One problem is that it requires a fairly substantial amount of memory and computational support, and is usually not found on the low end (less than $500) printers.

   3. PCL? (pcl or pcl@) PCL is another Print Language supported by many vendors, including Hewlett-Packard, Lexmark, and others. It is essentially text with escape sequences to tell the print engine to place markings on a page at specific places in a specific font. It is the second most common format used with modern printers.

   4. Text? (text or text@) Text is really just PCL without any control sequences. However, it is easy to have ifhp convert ordinary text into PCL by prefixing the appropriate PCL control codes. You may also need to use the crlf option to force CR to CR-LF translation. If you have a simple text printer then you may want to use the much easier to configure lpf filter from the LPRng distribution (http://www.astart.com/LPRng.html).

   5. Vendor Specific There is a growing trend to have very proprietary Print Languages for very low end (less than $300) printers. These printers usually require all of their jobs to be preformated by software running on the host and to have the job delivered to them in a specific manner. If you have one of these printers, you will need to get a rasterizing program that produces the correct format. Check to see if GhostScript, supports your printer. If it does then you can use GhostScript to translate PostScript to your printer's required format.

   
   
   

3. Memory Size. If you are going to be sending large print jobs or ones with a large amount of graphics to the printer, you will need a substantial amount of memory to deal with rasterization. Most high resolution Laser Copier based printers require a minimum of 16 megabytes for adequate performance, and if you are printing complex PostScript or PDF documents you may want at least 32 megabytes. Color printers require substantially more and 64 megabytes is not uncommon.

4. Communications. The connection between your printer and the host computer.

   1. Network Connection This is the most reliable and high speed way to connect a printer to a system. This is especially true if a printer must be accessible to multiple users and is located at a distance from the user.

   2. Parallel Port (status@) The parallel port is a unidirectional communications channel and does not do full duplex bidirectional communications. Some operating system support bidirectional communications, but they do so by requiring write operations to alternate with read operations.

   3. Serial Ports This is the very worst way to communicate at high speed with a printer. Serial ports usually have a high error rate, suffer from data overruns, and have a severe impact on system performance. You will need to configure your printer speed, format (bits per character, parity, stop bit), and flow control method, and then do the same for the host. This can be an endless source of frustration for the novice user.

   4. Print Server Box Many older printers do not directly support a network connection and have an external print server box attached to either their serial or parallel ports. If you have the printer connected to a parallel port, then you will still most likely only have unidirectional communication and no status information will be available from the printer.

   
   
   

4.2. Network Communication Protocols

The most high speed and reliable connection to your printer is using a network connection. The following protocols are usually used to communicate with a network printer: RFC1179 (TCP/IP printing), Socket Protocol (TCP/IP), AppSocket Protocol (TCP/IP), Novell Print Protocol (IPX), SMB Print Protocol (TCP/IP), and AppleTalk Print Protocol (TCP/IP).

It is highly recommended that you use TCP/IP networking to communications to talk to your printer, and that you do not enable any other protocol on your printer. If you have two different systems trying to connect to the same printer using different protocols, a wide range of vendor's hardware will lock up and may require a power up reset to recover. Documented evidence for this behavior includes a wide range of printers, including those from Hewlett-Packard, LexMark, IBM and other vendors.

Only the TCP/IP based network job transfer protocols are discussed in this document. For details on using other protocols, please consult the consult the LPRng documentation.

4.3. RFC1179 (BSD or TCP/IP) Job Transfer Printcap Entry

RFC1179 is used to transfer print jobs between a client (user) and a print spooler, or between two print spoolers. Jobs are transferred as a set of files, and the only information exchanged during the transfer process is the success or failure of the transfer. In order to get status about the actual job printing, a separate query status (lpq) is sent to the print spooler.

Many, if not all, printers with a network interface that supports the TCP/IP protocol support the RFC1179 protocol for job transfer. However, their support for print job status is usually minimal to non-existent. If you want to send a job to a printer using the RFC1179 protocol, please be aware of the following problems.

Normally a print spooler (System 5 lp, BSD lpd, LPRng) does not modify a print job when forwarding it to another print spooler. This means that your print job will normally pass from the originating lp or lpr program to the destination printer with no changes. This can have disastrous results if the job requires filter processing.

If you are using the LPRng print spooler, job transfers using RFC1179 is specified by using :lp=spoolqueue@host or :rp=spoolqueue:rh=host printcap entries. For example:

    raw:
      :lp=raw@host
      :sh:sf:mx=0
      :sd=/var/spool/lp
    cooked:
      :rp=cooked:rm=host
      :sh:sf:mx=0
      :sd=/var/spool/lp

No filters are specified as the job is not modified, only transferred from one server to another. Even if filters were specified they would be ignored. The lpd_bounce flag causes the LPRng spooler to pass the print job through the specified filter and then send the filter output to the actual network printer. The lpd print spooler will open a temporary file to hold the filter output, and then proceed to start the specified filter with its STDOUT attached to the temporary file, its STDIN attached to the file to be processed, and its STDERR redirected to an error log. The single resulting file is then transferred to the destination system using the RFC1179 protocol.

When a job is created the job format is specified (default is f), and a filter named by the :i<format> option is selected for use. For example:

    raw:
      :lpd_bounce
      :lp=raw@host
      :sh:sf:mx=0
      :sd=/var/spool/lp
      :ifhp=model=XXX,status@
      # for 'f' format
      :filter=/usr/local/libexec/filters/ifhp
    cooked:
      :lpd_bounce
      :rp=cooked:rm=host
      :sh:sf:mx=0
      :sd=/var/spool/lp
      :ifhp=model=XXX,status@
      # for 'f' format
      :filter=/usr/local/libexec/filters/ifhp

Unfortunately, some print spooling systems also use the v format by default. You may find the following printcap entry useful in this case. The :filter option specifies a default filter that is used if one is not specified for the format.

    raw:
      :lpd_bounce
      :lp=raw@host
      :sh:sf:mx=0
      :sd=/var/spool/lp
      :ifhp=model=XXX,status@
      # for 'f' format
      :filter=/usr/local/libexec/filters/ifhp

The lpr -l or lpr -b flag is used to specify that a job has the special binary flag. In this case, most filters will perform only the most perfunctory processing and pass the job directly to the printer.

4.4. Socket Protocol (TCP/IP) Operation Printcap Entry

Many printers with a network interface provide a TCP/IP port that is a direct connection to the internal print engine. If a TCP/IP connection is made to this port and a file is sent over this connection, then the print engine will process the file. More importantly, the connection is bidirectional, and the printer will report errors and status conditions over the connection. PJL and PostScript status request commands can be sent to the printer and the printer will respond with information.

The ifhp filter makes extensive use of this protocol, and provides support for status and error reporting. In cooperation with the LPRng print spooler, it will provide a detailed description of the actual print job progress and any error conditions that arise.

To use a Socket connection with LPRng, you use the :lp=host%port printcap entry shown below. The lpd print spooler will open a connection to the TCP/IP port on host and passes the (bidirectional) connection to the ifhp filter on file descriptor 1 (STDOUT) and the file to be printed on file descriptor 0 (STDIN). Errors and status information are reported by the ifhp filter on file descriptor 2 (STDOUT) and placed in the error status log by the lpd print spooler.

The connection made by the lpd server to the printer is persistent over the entire job; all file transfers for the same job are made over the same connection. This is important as it prevents other printer users from hijacking the printer in the middle of print a job and getting your job outputs mixed together.

The following is a typical printcap entry using the socket protocol.

    raw:
      :lp=host%9100
      :sh:sf:mx=0
      :sd=/var/spool/lp
      :filter=/usr/local/libexec/filters/ifhp

4.5. Appsocket Protocol (TCP/IP) Operation

The Tektronics Phaser Series printers and QMS printers use the Appsocket protocol when sending a job to the printer. This protocol uses two ports: a TCP/IP listening port which accepts TCP/IP connections and a UDP query port that is used to obtain status information. Unfortunately, the UDP port is almost totally useless for job monitoring and status purposes and is not used except in an advisory role.

The Appsocket protocol is (briefly):

1. When a UDP packet is received on the UDP port a reply packet containing the status is returned to the originator's address. This packet contains an status indication in an un-standardized format but usually is readable or has a clearly defined format.

2. To send a job to the printer, a TCP/IP connection is opened to the TCP/IP port and job data is sent. Only a single job can be sent at a time - a EOJ in the job, i.e.- CTRL-D for PostScript or ESC E for PCL will cause the printer to terminate reading from the TCP/IP port, and after job processing has finished, to close the TCP/IP connection. All input after the EOJ may be ignored by the printer and not processed.

3. While processing the job, if bidirectional support is available and has been enabled the printer will return job status or information until all of the print job which is has received has been processed. This support is usually not enabled by default and must be enabled by using a specialized administration interface or configuration tool.

4. Unfortunately, some printers will also close the connection when the EOJ has been received. These printers are virtually useless when trying to get error or status information about a job.

5. Even more annoying is the behavior of some printers that insist on the network connection remaining open until the job has been processed. The device sending the job to the printer must do a shutdown on the sending direction of the network connection, and then read status information from the receiving direction until the printer terminates the connection. Unfortunately, some printers do not terminate the connection, and the the user must close the connection after a suitable timeout.

6. While processing the job, the printer will ignore any connection requests, and only until the job has been processed will the printer accept connections.

7. During job processing, status and error indications can be obtained by sending a query to the UDP port. However, the error conditions and other information are not very precise as the status may change dramatically during job processing.

The Appsocket protocol does not use a persistent connection. If two people are sending jobs to the printer simultaneously it is very likely that the jobs will get intermixed.

The appsocket option causes the ifhp filter to open and close a TCP/IP connection to the printer. In order to reopen the device, ifhp needs the device name. It gets this from the PRINTCAP_ENTRY environment variable which has the device information, or by using the TCP/IP address of the initial end of the connection. The following is a sample printcap entry for this printer:

    # Phaser Setup
    #  Appsocket
    lp:server  
      :lp=10.0.0.1%9100  
      :sd=spooldir  
      :...  
      :ifhp=model=ps,appsocket
      #path to ifhp filter  
      :filter=/.../ifhp

For your convenience, the model=phaser entry is suitable for use with the appsocket protocol.

4.6. Common Print Server Boxes Configuration Information

The following is a list of print server manufacturers, models, and with hints on how to access these boxes with various protocols.

All company, brand, and product names are properties of their respective owners.

4.7. Timeout Problems Sending A Job

The ifhp filter may need to run a program such as ghostscript to do format conversion. For large files this can take quite a bit of time and most network printers have a connection timeout. If no data is received for this time the printer will close the connection. By default this timeout is fairly short: 30 or 90 seconds on most printers.

If you are sending large jobs to the printer using the socket protocol and are getting timeout problems due to conversion timeouts, then there are two solutions: a) use the Appsocket protocol, which will open and close the connection for each file, and only send data when the converted file is available, or b) do your conversions first and then spool the converted job to be sent directly to the printer. The second method requires an LPRng bounce queue.

    # Method a) Appsocket
    lp:server 
      :lp=10.0.0.1%9100
      :sd=spooldir 
      :... 
      :ifhp=model=printer,appsocket
      #path to ifhp filter 
      :filter=/.../ifhp 
    
    # Method b) Bounce Queue
    #  this queue does the conversion if required
    lp:server
      :lpd_bounce 
      :lp=real@localhost
      :sd=spooldir 
      :... 
      :ifhp=model=printer
      #path to ifhp filter 
      :filter=/.../ifhp 
    # this queue does transmission
    raw:server 
      :lp=10.0.0.1%9100
      :sd=spooldir 
      :ifhp=model=printer
      #path to ifhp filter 
      :filter=/.../ifhp 

For method a), the Appsocket protocol is used and the ifhp filter will be invoked before sending a job. For method b), you use two queues: a bounce queue that does the format conversion and then sends the job to the real queue, and the real queue that actually talks to the printer.

4.8. PS, PCL, PJL Printer with TPC/IP Network Interface

The most common TCP/IP protocols used for transferring jobs to network printers are RFC 1179, a direct TCP/IP socket, connection to the print engine, and the very odd Appsocket protocol described in previous sections. Here is a reprise of the various printcaps and methods to use them.

    # printer setup  
    #  force clients (lpr, lpq, to use server)  
    lp:lp=lp@serverhost  
    # server information  
    lp:server  
      :sd=spooldir  
      :...  
    
      # No filtering, transfer using RFC1179, use:
      :lp=queue@10.1.1.1
      #    or 
      :rp=queue:rm=10.1.1.1
    
      # Filtering and then transfer using RFC1179, use:
      :lpd_bounce:lp=queue@10.1.1.1
      #    or 
      :lpd_bounce:rp=queue:rm=10.1.1.1
      :ifhp=model=name
      :filter=/.../ifhp  
    
      # Filter, transfer using socket, use:
      :lp=10.1.1.1%9100 
      :ifhp=model=name
      :filter=/.../ifhp  
    
      # Filter, transfer using Appsocket, use:
      :lp=10.1.1.1%9100 
      :ifhp=model=name,appsocket
      :filter=/.../ifhp 

If your printer is a parallel port printer connected to an external Network Print Spooler such as an HP JetDirect box, then while the network connection to the Network Print Spooler is bidirectional the connection from the Network Print Spooler to the printer may be unidirectional and no status information will be returned from the Network Print Spooler. In this case you must add the status@ option to tell ifhp not to expect status:

    # Filter, transfer using socket
      :lp=10.1.1.1%9100 
      :ifhp=model=name,status@
      :filter=/.../ifhp

4.9. PS, PCL, PJL Printer with Parallel Port Connection

If your printer is connected to a bidirectional parallel port you may be able to read status from the printer. First, determine if your printer has bidirectional IO capability and if your operating system has support for it. If it does not, then do not use the :rw (open connection read-write) option to open the printer device in read write mode.

    # printer setup  
    #  force clients (lpr, lpq, to use server)  
    lp:lp=lp@serverhost  
    # server information  
    lp:server  
      # do now open read write
      :rw@
      :sd=spooldir  
      :...  
      # parallel port 
      :lp=/dev/lpt
      #path to ifhp filter  
      :filter=/.../ifhp 

If, on the other hand, your operating system reports that the parallel port is bidirectional and is able to read the printer model information, then you can try opening the parallel port read-write and seeing if the ifhp filter can read status information:

    # printer setup  
    #  force clients (lpr, lpq, to use server)  
    lp:lp=lp@serverhost  
    # server information  
    lp:server  
      # open read write
      :rw
      :sd=spooldir  
      :...  
      # parallel port 
      :lp=/dev/lpt
      #path to ifhp filter  
      :filter=/.../ifhp 

4.10. PS, PCL, PJL Printer with Serial Port

It is strongly advised that serial ports not be used for high speed data transfers. The main problem is trying to configure them in such as way that they do not lose characters due to data overruns or parity errors. LPRng is strongly deprecating support for serial port printers.

The LPRng print spooler will open and set the serial line characteristics, and pass the open connection to the ifhp filter. The tty connection must pass all 8 bits with no parity, and should use hardware flow control if at all possible. Unfortunately, the various stty options needed to do this vary from system to system. Also, you may discover that your serial connection does not support hardware flow control. If this is the case, then you will have to use software flow control which is rather unreliable for high speed (over 9600) serial lines due to the timing latencies involved.

    # printer setup  
    #  force clients (lpr, lpq, to use server)  
    lp:lp=lp@serverhost  
    # server information  
    lp:server  
      :sd=spooldir  
      :...  
      # serial port 
      :lp=/dev/ttyxxx 
      :stty=38400 -echo -crmod -raw -oddp -evenp \ 
         ixon pass8 -ixany cbreak crtscts 
      #path to ifhp filter  
      :filter=/.../ifhp 

4.11. PostScript Only Printer

The model=ps entry supports PostScript only printers.

    # printer setup  
    #  force clients (lpr, lpq, to use server)
    lp:lp=lp@serverhost 
    # server information  
    lp:server  
      :sd=spooldir 
      :...  
      :ifhp=model=ps 
      #path to ifhp filter  
      :filter=/.../ifhp 

If you have a unidirectional or write only (no status information) connection such as a parallel port you should use:

    :ifhp=model=ps,status@

Many PostScript printers recognize the PostScript EOJ marker (Control-D or \004) as an end of PostScript job indication and will perform page eject and other suitable actions. Unfortunately, strictly according to PostScript documentation this character is only allowed in the Serial Port Data Stream, and there are some printers that treat it as an error. In addition, the Control-T character is recognized as a printer status solicitation, and some printers do not return status or recognize it as an error.

If your printer does not handle PostScript EOJ (Control-D) at all, set ps_eoj@ to suppress generation of extra Control-D characters by ifhp. If your printer requires a Control-D at the end of the job but fails when they occur at the start of the job, set ps_eoj_at_start@. If the printer requires a Control-D at the start but not at the end, set ps_eoj_at_start@.

PCL based printers are not nearly as fussy. However, you may discover that some of them do not correctly handle a PCL EOJ at the start of a job in spite of all examples and documention. Use the pcl_eoj_at_start@ to suppress adding a PCL EOJ (Esc E) command string to the start of a PCL job file.

    :ifhp=model=ps,ps_eoj@

See the section on File Conversion Support for ways to print text and other files on a PostScript printer.

4.12. GhostScript

Generating a raster image from a PostScript or PCL file in a timely manner requires a high speed processor and substantial amounts of memory. Many of the low cost printers require the user's system to do the raster conversion and the raster file is then transferred to the printer. The file format is usually a subset of PCL.

The GhostScript program can process PostScript files and produce raster output for a wide range of devices. The ghostscript pcl_gs printer configurations is used with these printers. See GhostScript Printer for details.

4.13. Tektronics Phaser, QMS, and Appsocket Protocol

The Tektronics Phaser, QMS Network Printers, and a few others use the Appsocket protocol described in a previous section. The Tektronics (model=phaser) configuration entry has the required options for these printers:

    [ phaser qms ]
    appsocket
    ps
    pjl@
    pcl

The following shows a typical printcap entry:

    #  force clients (lpr, lpq, to use server)
    lp:lp=lp@serverhost 
    # server information  
    lp:server  
      :sd=spooldir 
      :lp=10.1.1.1%35 
      :...  
      :ifhp=model=phaser
      #path to ifhp filter  
      :filter=/.../ifhp 

5.1. Command Line Options

The most important options that LPRng passes and that ifhp uses are:

    Examples:
    ifhp "-Tmodel=ps,status@" "-Za4,landscape"

Since commas are used to separate options, whitespace is used to separate multiple values for a particular option. You will need to quote this on a command line. For example:

    ifhp "-Tfont=elite greek1 dingbat"

The ifhp program first checks to see if the PRINTCAP environment variable is defined. By convention, LPRng will place the printer printcap entry in this variable when it starts the ifhp filter. The printcap :ifhp=options value is extracted and used as the default -T options. After getting the options from the printcap, the -Toptions command line options are appended to the list of -T options. The single letter command line options are also made available to the ifhp programs as shown below:

    PRINTCAP=lp:ifhp=model=this,status@:...
    
    ifhp -n root -h localhost -Tmodel=that,debug=1
    
    Concatenated -T options:  model=this,status@,n=root,h=localhost,model=that,debug=1
    Resulting    -T options:  status@,n=root,h=localhost,model=that,debug=1

The -T option list is scanned from left to right, and later option values override earlier ones. The -T option values have priority over values that are obtained from the configuration file and cannot be overridden. There are several options that have important effects on the operation of the ifhp filter.

5.2. General Configuration Options - config, trace, debug

• config=Configuration file location

• debug=Debug options

• trace FLAG trace on STDERR

These options are used to control the global operation of the ifhp filter, and are only available from the -T command line options.

5.3. Status Messages

• statusfile=statusfile

• statusfile_max=maximum status file size

• statusfile_min=minimum status file size

• summaryfile=one line summary file

5.4. Printer Status Available - status

• status FLAG status available from device

The status option indicates that there is a bidirectional connection to the printer, and that status can be obtained from the connection. During initialization the ifhp filter will test the printer connection and determine if it supports reading. If it does not then ifhp will set status@.

5.5. Monitoring Options - sync, waitend, pagecount

The sync, waitend, and pagecount options are ignored if no status is available from the printer. The sync option specifies the method to use to determine if the printer is ready and operational. The waitend option specifies the method used to determine when a print job is finished. The pagecount option specifies the method used to obtain pagecount or status information.

5.6. User -Z Option Support

The ifhp filter provides a simple way for users to request a particular printer facility or option. The lpr -Zkey=value command causes the lpd print spooler to pass the -Z options on the ifhp command line.

The ifhp filter implements these options by first determining if they are allowed, and then using them to select a set of strings that are sent to the printer. Since some options are implement by sending PJL strings to the printer, some by PostScript, and some by PCL commands, the method of specifying and generating them is a bit involved.

The following facility is used to control the names and types of user options.

For each option, the actual string or set of strings is specified as follows.

The following user options are predefined in the default ifhp.conf file and are recommended for use.

5.7. Adding User Options

The following shows how to add a PJL option to an ifhp.conf file. By convention, the configuration is added to the end of the ifhp.conf file.

    [ newprinter ]
    pjl_user_opts += [ screen ]
    pjl_screen = PJL SCREEN = ON
    
    ps_user_opts += [ fuzzy ]
    ps_fuzzy = <</Fuzzy (\%s{fuzzy})>> setpagedevice

In the first example we define the screen option. The lpr -Zscreen option will cause the PJL command PJL SCREEN = ON to be put into the output to the printer.

Similarly, the lpr -Zfuzzy=5 option will cause the PostScript command <</Fuzzy (\%s{fuzzy})>> setpagedevice to be sent to the printer.

5.8. Initialization and Setup Control

Several options are used during the processing steps discussed in Filter Operation Details to control what setup is done for the printer.

These initialization options are very useful in order to set up information controlling the default format or options for a print job. For example:

    pcl_init = [ normalpage ]
    pcl_normalpage=[ letter crlf linewrap
      portrait clearmargins fixed pitch=10 courier ]

When processing a PCL job, normalpage is expanded by searching first for normalpage and then for pcl_normalpage; this in turn results in the expansion of the list of values. For example, pcl_crlf is usually defined as pcl_crlf=\033&k2G, which is the PCL command to translate a New Line (\015) character as a Carriage Return/New Line. The other entries have similar definitions that produce the desired effects.

6.1. Configuration File Entries

The ifhp filter uses a simple text based configuration file, usually /usr/local/etc/ifhp.conf or /etc/ifhp.conf to get a set of configuration values which control its operation. The following sample configuration file segment shows how information is specified.

    # comment line - first non-blank character is a #
    #---- DEFAULTS ----
    # we first have the default section
    #   - a flag option whose value is 1
    on_flag
    #   - a flag option whose value is 0
    off_flag@
    #   - a flag option whose value is a string (single line)
    #     its value will be 'this is a string'
    strval = this is a string
    #   - a flag option whose value is multiple lines
    #     each additional line starts with whitespace
    #     value is 'this\nis1\na\nstring'
    longstrval = this
     is\061
     a
     string
    #   - and a list that gets expanded -
    #     '[ this ] [ is a\nlist ]' -> [ this is a list ]
    longlist = [ this ] [ is a
     list ]
    #    we can extend a string.
    #    strval will  now be 'this is a string added'
    strval += added
    #    and we can expand a list
    #     '[ this ] [ is a\nlist ] [ more ]' -> [ this is a list more ]
    longlist += [ more ]
    
    # a printer specific section
    # ---- PRINTER ----
    [ hp hp4* ]
    # this match model=hp, model=hp4, model=hp4x
    # override the default
    onflag@
    include /usr/local/etc/ifhp.conf.local
    
    [ entry1 ]
    value
    [ entry2 ]
    tc=entry1

6.2. Comments

Comments are lines whose first non-whitespace character is #. Use \# if the first non-whitespace character must be #.

6.3. Option Setting

    Syntax             Equivalent To
    option                     option=1
    option@                    option=0
    option=val
    option=[ v1 v2  ... ]      value contains all whitespace
    option=[ v1                up to the next option entry
     v2                        blank lines and comments
     v3                        are not included
     ]
    option=v1
     v2
     v3

If an option's default value is the empty string (''). The ifhp program uses the Perl language convention that this value is equivalent to 0 when used in a numerical context or the empty string when used in a string context.

In general when a string is used in an integer context it is converted to a the appropriate numerical type using the standard Perl/C numerical representation and conversion methods.

The flag syntax sets the value of flag to the string '1', that is, the string with a 1 value, and flag@ sets it to '0'.

The option = value syntax sets the option value to a string. The string can extend across multiple lines. A line starting with a space has its value appended to the previous option with a new line (\n) separator.

As shown in the example, the += operator is used to append to a string value. The [ option option ...] syntax is used to specify that the value is a list. Lists are used to specify a list of options which can be flags or string values. Lists have the property of recursive evaluation which means that the individual list items will be further processed during printing. This is discussed later in detail.

The include facility is currently deprecated, and may not be implemented in future releases. It will cause the specified file to be read and processed at that point in the configuration file.

6.4. Option Use

Options and their values are used to control printer operation. There are two types of options: those with a predefined or builtin meaning to the ifhp filter and those which have their values sent to the printer when appropriate. The builtin options are listed and their use is explained in later sections.

6.5. List Expansion

The ifhp filter configures a printer by sending the values of options to the printer or performing built-in operations. An option can have a flag, string, or list value.

A LIST value has the form [ v1 v2 ... ]. When a list value is to be sent to the printer each of v1, v2, etc. is expanded in turn and the corresponding string value or builtin action is carried out. If the string value of a term is itself a list, the list will be expanded in turn. Recursive list evaluation will result in an error. The following is an example of list expansion:

    t1=[ p1 p2 ]
    p1=this is
    p2=[ p3 p4 ]
    p3=a
    p4=test

The option t1 is expanded by expanding p1 and then p2; The expansion of p1 produces "this is", and p2 produces [p3 p4]. This list is then expanded to produce "a" and "test".

Some LIST options are used in printer language specific contexts and their values are processed appropriately. For example, pjl_init=[...] specifies a set of initialization operations for PJL printers, and pcl_init=[...] is used to specify the initialization needed for PCL printing. The expansion of the LIST entries is done in the language specific context. For PJL this requires that the output be well formed PJL commands, and for PCL that all whitespace be removed.

The context dependent expansion is required because sometimes it is necessary to do operations both using PJL and PCL or PJL and PS combinations to ensure correct printer operation. During expansion the language name and an underscore is prefixed to the list entry name and this is used as the option name during expansion. If the prefixed name is not found then the unprefixed name will be used. For example, suppose that we have:

    pjl_init=[ initstr test ]
    pcl_init=[ initstr ]
    pjl_initstr=@PJL ECHO YES
    pcl_initstr=\033(*0V
    test=DONE

When PJL initialization is being done and we want string values for the pjl_init LIST, we expand initstr and test in the pjl_ context. First a defined pjl_initstr value will be looked for and then a defined initstr value. Since there is a value of pjl_initstr it will be used.

Similarly we will check for pjl_test and test values. Since pjl_test does not have a defined value the test value DONE will be used.

When PCL initialization is being done and we want string values for the pcl_init LIST, then we expand initstr in a similar way, resulting in \033(*0V.

We can use the list entry [ option=value ] to temporarily specify the value of a variable which is then used during language specific expansion. For example, suppose that we have the following set of definitions:

    pjl_init=[ initstr=testing ]
    pjl_initstr=@PJL INIT=\%s%lcub;initstr%rcub;XQ

As discussed in the next section, the \%s%lcub;initstr%rcub; will cause the value for the initstr value to be substituted into the pjl_initstr string. How this is done is discussed in the section on String Escape Sequences.

6.6. String Escape Sequences

String values have a syntax similar to PERL or C. The \ (escape) character indicates the start of an escape sequence string. This has the syntax:

6.7. Language Context and Value Expansion

The ifhp filter sends initialization and configuration commands to the printer. Depending on the type of language of a print file (i.e. - PostScript or PCL), different command formats would need to be used to implement different options. For example, to implement a landscape option for a PJL aware printer you would need to send the PJL command @PJL SET ORIENTATION=LANDSCAPE. For a PostScript printer you would need to send a very strange string which would depend on the actual printer mode.

Our language context also includes various checks for language specific dependencies. This section refers to material that is discussed in depth in later sections of this document, and on first reading may be a little confusing. However, if you are not aware of some of these restrictions then much of the information in the configuration files may be very confusing.

6.8. Printer Entries

The ifhp.conf file is divided into printer entries by [ pattern pattern ...] lines. Each pattern is glob matched against the model option value, and if the match is successful then the options on the following lines until the next printer entry header are appended to the specific printer configuration entry.

By convention, each configuration file is assumed to start with the header [ default ], and the initial set of lines are used to set default values for the various ifhp options.

The algorithm for scanning the configuration files first sets the model value to default, and extracts the default information. It then sets the model value to the user specified value, and rescans the configuration file information.

If users need to add or modify the ifhp.conf file, then they should add their entries to the end of the file, and override any default options by specific values in their new entry. To aid with system configuration and maintenance, the distributed ifhp.conf file has the following text at the end of the file:

    ##### This is the end of the standard ifhp.conf file.
    ##### Add your local files after this
    ##### If you want to override some entries, simply change the names to
    ##### something different, i.e. hp4 hp4.old
    ##### Here is a script to do this and then append your local file to the
    ##### end of the ifhp.conf file:
    #####
    ##### #!/bin/sh
    ##### for i in $* ; do
    #####   perl -spi.bak -e 's/ $i / $i.orig /g' ifhp.conf
    ##### done
    #####
    ##### sed -n -e '1,/XXX END XXX/p' ifhp.conf >ifhp.conf.new
    ##### sed '1,/XXX END XXX/d' ifhp.old >> ifhp.conf.new
    #####
    ##### You can probably improve on this.
    #####
    #### XXX END XXX #####
    
    # user adds new default values here for all printer entries
    [ default ]
    # set default value
    pcl_option= \033test
    
    [ mypcl_printer ]
    # override default value
    pcl_option=

6.9. Include Facility

The include filename facility is similar to the standard compiler file inclusion facility. The specified file or list of files separated by commas or whitespace will be substituted for the indicated line.

6.10. tc Entry Inclusion Facility

The tc=entry facilty is similar to the printcap tc facility used in the LPRng software other places. The specified entry or list of entries separated by commas or whitespace will be substituted for the indicated line.

7.1. Filter Pseudo-Code

The details of the filter operations are described in the following pseudo-code. The sections marked with ### are discussed later in this document in detail.

/// See: Options, Initialization and Setup

    ###+++ Initialization and Setup
    // get ifhp information from PRINTCAP_ENTRY environment variable
    if( PRINTCAP_ENTRY environment variable has a value ){
        split printcap information into printcap fields
        if( :ifhp=options,options is present in printcap ){
            split the options list and place in the Toptions list
        }
    }
    Add the -T command line options to the Toptions list
    Add the -Z command line options to the Zoptions list
    foreach option in -Toptions do
        if( option = "debug=level" ){
            set Debuglevel = level;
        }
        if( option = "trace" ){
            output error and trace on STDERR
        }
        if( option = "config=pathlist" ){
            set configuration pathlist = pathlist;
        }
        if( option = "model=name" and model not set ){
            set model = name;
        }
    }
    Read the configuration files from the config file list
    Prepend each file with a [ default ] header
    
    Scan the configuration files for [ default ] entries;
      later entry values will override earlier ones.
    
    Repeat the scan, but this time search for [ model ] entries
      matching the specified model.
    
    Put the command line options and -T options into configuration
      information, effectively overriding the information from the
      configuration files.
    
    if( appsocket ) {
       Get the :lp=... entry from the PRINTCAP_ENTRY environment variable
       if( no information ) {
           use the getpeername() to get the TCP/IP address of the current
           connection.
       }
       if( no informtion AND no dev=... parameter ) {
           error!
       }
       close connection to printer and set -Tdev= device or IP Address
    }
    
    // open a connection to the printer if required
    // usually only done when appsocket protocol is used
    if( device specified using -Tdev=device ){
        close(1)
        // if device is host%port, we open TCP/IP connection
        fd = open(device);
        // Note - status  opens RW
        //        status@ opens WO
        dup fd to 1; close fd;
    }
    
    ###---

    ###+++ Synchronization and Pagecount
    if( status returned by printer and sync requested ){
        do{
            send command and wait for timeout;
        } while( no response );
        if( appsocket ){
            close and reopen TCP/IP connection;
        }
    }
    
    
    if( status and pagecount requested ){
        // pagecount has the form pagecount@ (none),
        //   pagecount=ps, pagecount=pjl, ...
        if( pagecount=language has value ) do {
            if( pagecount TRUE ){
                set pagecount= pjl or ps depending on availability
            }
            if( pagecount = pjl and PJL INFO available ){
               send PJL INFO PAGECOUNT command to printer
            } else if( pagecount = ps ){
               send PS program to printer
            } else {
                terminate with error;
            }
        } while( no pagecount response );
        if( appsocket ){
            close and reopen TCP/IP connection;
        }
    }
    ###---

    ### PJL INITIALIZATION
    if( PJL enabled ){
        language = "pjl_"
        foreach option in pjl_init=[...] {
           expand the option using the language value
           #+++ PJL OPTION ACTIONS +++
           if( option in pjl_vars_set=[ ... ]
             and option not in pjl_vars_except
             expand "@PJL SET OPTION=\%{option}"
             output = expanded string value
           } else {
             if( option value is a string ){
               output = expanded string value;
             }
           }
           // output has the form @PJL COMMAND ....
           if( COMMAND is in pjl_only=[ ... ]
               and not in pjl_except=[ ... ] ){
               send output to printer
           }
           #--- end PJL OPTION ACTIONS
        }
        if( !OF_mode ){
             foreach option in -Toption=value {
                if( option in pjl_user_opts ){
                    #+++ USER PJL OPTIONS
                    // join 'pjl_' and the option name
                    expand 'pjl_' . option
                    // perform PJL actions as above
                        #+++ PJL OPTION ACTIONS +++
                        ....
                        #-- PJL OPTION ACTIONS +++
                    #--- USER PJL OPTIONS
                }
             }
             foreach option in -Zoption=value {
                if( option in pjl_user_opts ){
                    // perform USER PJL actions as above
                    #+++ USER PJL OPTIONS
                    #--- USER PJL OPTIONS
                }
             }
        }
    }
    
    ###--- PJL INITIALIZATION

    // language is set to the type of job language
    // - PS, PCL, TEXT, RAW, UNKNOWN
    //  the first part of the job file is read and the filter takes
    //  a (wimpy) guess at the job file based only on the first couple
    //  of characters;  language is  be PJL, PS, or TEXT, or RAW
    //  This is the same algorithm as the UNIX FILE utility
    
    language = default_language (from configuration);
    if( command line -c (binary) option present ){
        language = RAW;
    } else if( -Zlanguage=xxx option present ){
        language=xxx
    } else if( forceconversion set ){
        use UNIX file utility to get file type
    } else if( file is PS file ){
        language=PS
        if( file starts with PS EOJ (CTRL-D)
            and ps_eoj_at_start is clear ){
            remove the PS EOJ
        } else {
            send a PS EOJ first
        }
    } else if( file is PCL file ){
        language=PCL
        if( file starts with PCL EOJ (ESC E)
            and pcl_eoj_at_start is clear ){
            remove the PCL EOJ
        }
    }
    if( file conversion table specified then ){
        look up file type in conversion table;
        if( conversion program specified ){
            run input through conversion program
        }
        set file type to output type
    }
    
    
    if( language = TEXT and PCL allowed ){
        language = PCL;
    }
    
    if( language not recognized by printer ){
        exit with error;
    }
    
    if( PJL ENTER supported ){
        use PJL ENTER command to select language;
        send nullpad NULLS to force full buffer condition
    }

    // LANGUAGE SPECIFIC INITIALIZATIONS
    if( language = PCL ){
        foreach option in pcl_init {
            ###+++ expansion
            do expansion similar to PJL OPTION actions
                using "pcl_" prefix for option lookup;
            ###---
        }
        if( not in OF_MODE ){
            foreach option in -Toption do {
                if( option in pcl_user_vars=[ ... ] ){
                ###+++ expansion as above
                ###---
            }
            foreach option in -Zoption do {
                if( option in pcl_user_opts=[ ... ] ){
                ###+++ expansion as above
                ###---
            }
        }
        remove whitespace and expand string results;
    } else if( language = PS ){
        ###+++ language specific actions as above,
          using the ps_ prefix for lookup
          allow only user option in the ps_user_opts list
        expand string results but do not remove whitespace
    }

    Transfer job to printer, reading error and other information
      back from the printer if enabled
    
    if( language = PCL ){
        send PCL End of Job
    } else if( language = PS ){
        send PS End of Job
    }
    
    
    // job termination
    
    ###+++ Synchronization and Pagecount as above
    finished = 0
    while( waitend and not finished ){
        // timeouts and retries are done here
        if( time taken is too long ){
            give up and report an error
        }
        if( waitend with PJL ){
            wait for end of job using UINFO;
        } else if( waitend with PS ){
            send PostScript echo program to printer
            if end_ctrl_t then add ^T
        }
        wait for response
        if( response has end of job indication ) {
            finished = 1;
        }
    }
    if( pagecount ){
        if( appsocket ){
            close and reopen connection;
        }
        get pagecount using previously described algorithm
    }
    
    ###---
    
    exit

7.2. Options, Initialization and Setup

During the setup step, the ifhp system will extract command line options and scan configuration files for printer entries. These operations are covered in detail in other sections.

7.3. Languages Supported- pjl, pcl, ps, and text

• pjl FLAG PJL Supported

• pcl FLAG PCL Supported

• ps FLAG PostScript Supported

• text FLAG Text Supported

These flags set the languages that are recognized or processed by the filter.

    @PJL JOB NAME = "..." [ START = nnn ] [ END = mmm ]

    @PJL EOJ NAME = "..." [ START = nnn ] [ END = nnn ]

    @PJL ENTER LANGUAGE = PCL
    @PJL ENTER LANGUAGE = POSTSCRIPT

    remove_ctrl=CT

    C\001\003   ->  \001\115\103\001\101\001\103 or \001MC\001A\001C

7.4. Synchronization and Pagecounts

• accounting= accounting program

• accounting_info= accounting information

• pagecount FLAG or Option pagecounter available

• pagecount_interval= get pagecounter interval

• pagecount_timeout= get pagecounter timeout

• pagecount_start= get pagecounter at job start

• pagecount_end= get pagecounter at job end

• pagecount_ps_code= PostScript to get pagecounter

• sync FLAG or Option sync required

• sync_interval= do sync at interval

• sync_timeout= sync timeout

• wait_for_banner FLAG wait for banner page

Many printers are able to provide status information back to the filter. It is assumed that in these circumstances file descriptor 1 (FD1) is bidirectional and status information can be read from it. When the status option is TRUE, FD1 is readable and is a device or communications socket, then the filter assumes that it can read FD1.

Synchronization is usually done in order to ensure that a previously spooled job or printer action has completed correctly, and the printer is ready to accept a new job. It is usually carried out by sending a request to the printer to echo a string back to the filter. Clearly, if the printer cannot provide status or echo values back, then synchronization is impossible.

The value of the sync option determines if a PJL ECHO command or simple PostScript program is used. The PostScript program has the form:

    \004%!PS-Adobe-2.0
    ( %%[ echo: TODSTR ]%% ) print () = flush
    \004

To control obtaining synchronization, the sync_interval=nnn and sync_timeout=nnn options are used. The PJL or PS command is repeated at sync_interval=nnn second intervals; if nnn is 0, then it is sent only once. If synchronization is not obtained within sync_timeout=nnn seconds, then the filter exits with an error status. A 0 value or sync_timeout@ disables timeouts.

When the ifhp filter is operating in OF mode and the wait_for_banner option is true, the filter will wait until it determines that the banner page has been completely printed before carrying out other filter functions.

Pagecounts are used to do accounting and report the number of pages used for a job. Most printers have a hardware based pagecounter mechanism whose value can be read by the appropriate PJL command or PostScript program. For example, if the PJL INFO command

    @PJL INFO PAGECOUNT

    pagecount_ps_code=
      /p {print} def ( %%[ pagecount: ) p
      statusdict begin pagecount end 20 string cvs p
      ( ]%% ) p () = flush

The lpd print server and the ifhp filter must act in coordination to do reliable pagecounting. The following options are used by the ifhp filter to assist with this:

The following options are used in the LPRng printcap entry to assist with getting the pagecounter values:

    lp:
      # run at job start
      :as=/.../accounting_at_start
      # run at job end
      :ae=/.../accounting_at_end
      # -a filter option value or last command line argument
      :af=/.../acct
      # default filter
      :filter=/.../ifhp
      # of filter - run before and after job, can be suspended
      # desperation flag for desperate situations
      #:suspend_of_filter@
      :of=/.../ifhp
      #options
      :ifhp=...,of_options=pagecount waitend

The :as program is run at the start of a print job, and is used to determine if the user has sufficient resourses to print a job. The :ae program is run at the end of a print job and is used to collect the accounting statistics. The ifhp filter will write accounting information to the accounting file specified by the command line -a option, or the last command line argument. When both the :of filter and normal filters are used together, the accounting information will be nested as shown.

    Normal Mode:
      start                     '-qProcessID' '-pPagecounter' \
         '-tStartTime' '-Pprinter' '-Hhost' '-nuser' '-Raccntinfo'
      end '-bPages' '-Telapsed' '-qProcessID' '-pPagecounter' 
         '-tEndTime' '-Pprinter' '-Hhost' '-nuser' '-Raccntinfo' \
         '-TElapsedTime'
    
    OF Mode:
      filestart                     '-qProcessID' '-pPagecounter' \
         '-tStartTime' '-Pprinter' '-Hhost' '-nuser' '-Raccntinfo'
      fileend '-bPages' '-Telapsed' '-qProcessID' '-pPagecounter' \
         '-tEndTime' '-Pprinter' '-Hhost' '-nuser' '-Raccntinfo'
         
    
    Sample Accounting File Entry:
    
      start '-q10699' '-p234' '-t2000-05-24-09:27:47.784' \
          -Plp -Hh4.private -npapowell
      filestart '-q10700' '-p234' '-t2000-05-24-09:27:47.784' \
          -Plp -Hh4.private -npapowell
      fileend '-b0' '-T1' '-q10700' '-p235' '-t2000-05-24-09:27:47.863' \
          -Plp -Hh4.private -npapowell
      end '-b1' '-T1' '-q10699' '-p235' '-t2000-05-24-09:27:47.863'
          -Plp -Hh4.private -npapowell

The format of the information written to the accounting file is controlled by the accounting_info=AHPn ifhp configuration value. If they are present, the specified ifhp command line flags are appended to the end of the standard accounting information. The accounting=... option specfies a program to run at then end of the job. This program has all of the accounting information passed as command line options. The program should exit with a 0 exit code; otherwise the results are undefined.

The printcap :suspend_of_filter controls how the lpd spooler manages the of filter. When a file is to be printed normally, a special two character suspend message (\031\001) is written to the filter STDIN. When the ifhp filter detects this string in the input it is required to suspend itself by sending itself a SIGSUSP signal. The :suspend_of_filter@ flag causes the lpd process to close the :of filter rather than suspending it, and to start a new :of filter process when it needs one. This option is used when there can be at most one process communicating with the printer, or when the ifhp filter must totally reinitialize the printer at job end.

The pagecount option controls if and how the pagecounter value will be fetched. Currently pagecount=ps (PostScript) and pagecount=pjl (PJL) are supported. The pagecount form will use PJL if it is available; otherwise PostScript if it is available. The pagecount@ suppresses pagecount operation. The pagecount_start and pagecount_end flags control if the pagecounter will be obtained at the start and end of the print job.

One of the major problems with getting printcounter values is that the print job must be totally finished or at least have all of its pages run through the paper feed stream when the pagecounter value is reported. Unfortunately, most manufacturers do not provide accurate ways to coordinate the two activities. The waitend option is used to enable the ifhp filter to send special command sequences to the printer which will detect the true end of job, but this may not be possible on many printers.

The printcounter_poll=N (default 1) option provides a method to deal with these types of printers. Commands to get the printcounter value are sent to the printer, and repeated at printcap_interval second intervals until the printcounter value has been stable for N readings.

The PJL TEOJ (True End Of Job) command has been used with only limited success to force End of Job reporting only when the job has finished. This can be sent to the printer during PJL initialization by specifying it as one of the PJL initialization strings:

    pjl_init=[ ... teoj ... ]
    pjl_teoj=@PJL TEOJ=ON

The of_options are used to modify the actions of the ifhp filter when it is running in OF Mode.

The pagecount_start and pagecount_end (both default to TRUE or ON) control if pagecounter values are obtained at the start or end respectively of the job.

The pagecount request is sent to the printer every pagecount_interval=nnn second intervals; if nnn is 0, then it is sent only once. If no pagecount value is obtained within pagecount_timeout=nnn seconds then the filter exits with an error.

7.5. PJL Initialization

• pjl_init=[ ... ] pjl initialization

• startpage= start page to print

• endpage= end page to print

• pjl_only=[ ... ] pjl commands supported

• pjl_except=[ ... ] pjl commands not to be used

• pjl_vars_set=[ ... ] pjl variables supported

• pjl_vars_except=[ ... ] pjl variables not to be used

• pjl_user_opts=[ ... ] pjl options available to user

If a printer supports PJL, the many printer operations can be initiated and controlled using PJL commands. Unfortunately, not all printers support the same set of commands. In addition, not all printers support the same set of operations or options. A PJL command has the form:

    @PJL COMMAND OPTION OPTION ...

    @PJL SET var = value ...

Similarly, when sending a command to set a PJL variable, the pjl_vars_set and pjl_vars_except lists are checked to determine if the variable name is in pjl_vars_set and not in pjl_except list. If the tests fail, then tne command is not sent.

If PJL is enabled, then the following actions are taken.

1. PJL Universal Exit Language (UEL) \033%-12345X is sent to the printer.

   This is required to ensure that the following PJL commands are accepted.

2. PJL JOB command is sent at the start of job. The JOB command can be used to select pages or impressions to be printed. If the -Zstartpage=nnn or -Zendpage=mmm option is present, then the PJL JOB command has the form:

       @PJL JOB START=nnn END=mmm
   

   
   
   

3. The pjl_init=[ ... ] value option is expanded using the PJL ("pjl_") language context as described above.

4. The -Toption=values and -Zoption=values are scanned for matching option names in the pjl_user_opts=[ ... ] list. If they are found, then the options are recursively evaluated in the PJL language context. The expansion algorithm will cause the option value to be used to set PJL variables. For example:

       Configuration:
         pjl_vars_set=[ OUTBIN AUTOSELECT JAM=YES ]
       
       Command
         ifhp -Zoutbin=upper,autoselect,jam
       
       PJL command generated:
         @PJL SET OUTBIN=UPPER
         @PJL SET AUTOSELECT=ON
         @PJL SET JAM=YES
   

   
   
   

7.6. File Conversion Support

• forceconversion FLAG force use of file utility

• default_language= default job language

The lpr -l or lp -b flags indicate that the spooled files are not to be processed by an output filter. The LPRng spooler recognizes this option and passes the -c command line option to suppress any language specific processing for files.

However, many PostScript printers cannot handle text files, and produce many hundreds of pages of garbage output if they are sent to the printer without being translated into PostScript, and some printers require language specific setup in order to print PCL, PostScript or text files correctly.

The ifhp filter has builtin tests for PJL, PCL, and PostScript files. These tests are almost identical to those used by many printers which do autodetection. If you need to recognize a wider range of file types, you can configure ifhp to use the UNIX file(1) program.

Finally, some printers have a very specialized job format that requires conversion to by a rasterizer program. This is handled as detailed in the following sections.

    ##forceprocessing - check all files for type - default 'no'
    forceprocessing@
    ## default
    default_language=text
    ## force only use of file program
    ## default is to let ifhp try first, then try file
    forceconversion@
    ##  file utility path
    file_util_path=/usr/bin/file -

    file_output_match = [
      *postscript*  ps  \%s{ps_converter}
      *pcl*         pcl  \%s{pcl_converter}
      *pjl*         pjl  \%s{pjl_converter}
      *printer*job*language* pjl
      *text*  pcl  \%s{pcl_converter}
      *gzip_compressed*  filter  \%s{gzip_decompresser}
      ]

    file_output_match = </pathname

    # set up GhostScript
    gs_device=epsonc
    gs_options=-r1440
    gs=/usr/bin/gs
    gs_converter= [ \%s{gs} -dBATCH -q -sOutputFile=- \
      -sDEVICE=\%s{gs_device} \%s{gs_options} - ]
    # use GhostScript for conversion
    ps_converter = [ \%{gs_converter} ]
    text_converter= [/usr/bin/a2ps -q -B -1 -M Letter \
      --borders=no -o- \%s{ps_converter} ]
    gzip_decompresser = [ /usr/bin/gzip -c -d ]
    
    [ ghostscript gs ]
    file_output_match = [
      *postscript*  ps  \%s{ps_converter}
      *text*  pcl  \%s{pcl_converter}
      *gzip_compressed*  filter  \%s{gzip_decompresser}
      ]
    
    Printcap entry:
    
    pr:
      :ifhp=model=ghostscript,gs_device=laserjet,gs_options=-r300x300

    #!/bin/sh
    # /usr.../wrapper path [options]
    # wrapper script for a2ps, enscript and others
    #   path is the path to the program and options are the
    #   options to pass.  The program is run and then the exit
    #   code is corrected
    "$@"
    status=$?
    case "$status" in
        1 ) exit $status ;;
    esac
    exit 0

    ifhp -Tcrlf

    file_output_match = [
     *text*  pcl
     ]

    file_output_match = [
     *  raw
     ]

7.7. GhostScript Printer

Generating a raster image from a PostScript or PCL file in a timely manner requires a high speed processor and substantial amounts of memory. Many of the low cost printers require the user's system to do the raster conversion, and a raster file is then transferred to the printer. These files are usually in a proprietary format. The GhostScript program can process PostScript files and produce raster output for a wide range of devices. See the GhostScript documentation for details. Some printers have PCL support but do not support PostScript. The gs and pcl_gs printer configuration support these printers.

    # PRINTER ghostscript - Printer with GhostScript conversion to raster files
    gs_converter= [ /usr/bin/gs -dSAFER -dBATCH -q 
       -sOutputFile=- -sDEVICE=\%s{gs_device} \%s{gs_options} -
     ]
    text_converter= [ /usr/bin/a2ps -q -B -1 -M Letter --borders=no -o-
     ]
    
    [ ghostscript gs ]
    pcl@
    pjl@
    ps
    text@
    file_output_match = [
    # PostScript to Raster
      *postscript*  raw  \%s{gs_converter}
    # text to PostScript to Raster conversion
      *text*  filter  \%s{text_converter}
      ]
    
    # PRINTER pcl_gs - PCL Printer with GhostScript conversion to raster files
    [ pcl_gs ]
    pcl
    pjl@
    ps
    text@
    file_output_match = [
    # PostScript to Raster
      *postscript*  raw  \%s{gs_converter}
      *pcl*  pcl
    # text to PostScript to Raster conversion
      *text*  filter  \%s{text_converter}
      ]

The \%s{gs_device} and \%s{gs_options} parameters can now be specified in the printcap. The following shows a typical printcap entry for use with this entry.

    #  force clients (lpr, lpq, to use server)
    lp:lp=lp@serverhost 
    # server information  
    lp:server  
      :sd=spooldir 
      :lp=/dev/lpt0     
      :...  
      :ifhp=model=gs,gs_device=epson,gs_options=-r240x72 
      #path to ifhp filter  
      :filter=/.../ifhp 

The ifhp configuration entry uses GhostScript to do the rasterization of the PostScript file, and the a2ps program to do a text to PostScript conversion.

7.8. Language Specific Initialization

• ps_init= PostScript initialization steps

• pcl_init= PCL initialization steps

After determining the output file language type, language specific operations are then carried out by expanding the language_init=[ ... ] options in the language context, and then the options in the -Toption=value and -Zoption=value command line options. The -T options are expanded before the -Z, allowing the -Z actions to override any set by the -T actions.

As mentioned elsewhere, the reason for the language specific processing is to allow different actions for the same command line option, depending on the file type that is being processed. For example, when processing a PCL file it might be necessary to send PCL command strings and when processing a PostScript file, you would need to send PostScript commands.

7.9. File Transfer and Error Status Monitoring

• logall FLAG log all printer status

• pjl_error_codes TABLE PJL error code translations

• pjl_quiet_codes TABLE ignore these PJL error codes

• pjl_alert_codes TABLE alert operation on these PJL error codes

• pjl_alert_handler TABLE program to alert operator

If the printer can return status, i.e., the status option is on, the filter will read status information from the printer.

If the logall flag is SET, then all error messages will be written to the status or log file.

If the printer is returning PJL status information, then this has a specific format:

    @PJL UINFO DEVICE
    CODE=nnnn
    DISPLAY="value"
    ...
    
    @PJL UINFO JOB
    START
    ...
    
    @PJL UINFO JOB
    END
    ...

The ifhp program will extract the CODE and job start and end flags, and log these as appropriate.

Unfortunately, some PJL based printers are extremely verbose in their generation of status messages. In order to reduce the amount of logging of redundant information, ifhp will only record when a device status has changed, rather than when it has been reported.

The pjl_quiet_codes=[ code code code ] value is used to suppress reporting of selected error codes. If the error code is in the pjl_quiet_codes list, then the error status will not be reported to the user unless the logall option is set. The list of values is used as glob patterns. For example:

      pjl_quiet_codes=[ 10000 10001 10003 10023 10024 35078 41* ]

Also, there may be error codes which do not have a builtin error message available. New messages can be added using the pjl_error_codes option. Its value is a list of lines, each line consisting of an error code followed by the corresponding error message:

    pjl_error_codes=[
       code=msg
       code=msg
       ...
    ]
    
    Example:
      pjl_error_codes=[
         10000=powersave mode
         10001=Ready Online
         10002=Ready Offline
         10003=Warming Up
         10004=Self Test
         10005=Reset
      ]

Finally, there are codes or classes of codes that require operator intervention. These are specified using the pjl_alert_codes, and the pjl_alert_handler program will be invoked to send them to the appropriate destination. The formated error message will be available on STDIN for the handler. For example:

    pjl_alert_codes=[ 41* 42* 23* ]
    pjl_alert_handler=/usr/local/libexec/filters/alert_handler

7.10. End of Job

• waitend OPTION wait for job completion status

• waitend_interval= query for end at this interval

• waitend_ctrl_t_interval= send CTRL-T at this interval

The waitend option controls the job termination sequence. By default, this will do the same work as the sync operation, and the option takes the same set of values.

If waitend is suppressed using waitend@, then as soon as a job has been transferred, the next step, pagecount, will be attempted. If the print job has not finished at this point, then erroneous page counts will be reported.

When the appsocket protocol is used, suppressing waitend will cause no error messages from the printer to be reported.

Some printers do not have a True End Of Job reporting capability using PJL. This means that the job will be reported as done, but paper is still moving through the print engine. If you try to get pagecounts at this point you will get the wrong value. An alternative method is to set waitend=ps and The end_ctrl_t=word:word:... This will cause a CONTROL-T to be sent to the printer, a PostScript convention that will cause the PostScript interpreter to return the actual printing status. In most printers this will be printing or something other than idle or busy as long as paper is moving in the print engine. When status is returned, the words in the end_ctrl_t=word:word:... list value are examined for a match. If the status word is present then the end of job condition is assumed.

The waitend_interval value controls how often the waitend operation is repeated. This is usually set to a fairly large value, as it is normally used only to recover from printer failures such as users turning the printer on and off.

The waitend_ctrl_t_interval controls how often the printer is queried for status using CTRL-T and is usually set to a short (2 or 3 second) value.

7.11. Tektronix Phaser, QMS and AppSocket Support

• appsocket FLAG connect to printer and use AppSocket Protocol

The appsocket flag is used to specify that data transfer will be done using the AppSocket protocol. The ifhp filter will open a connection to the ip address and port specified by the dev=host%port option and carry out the various operations that it needs to do.

Normally after sending information to the printer a close() operation is done on the network connection. This will usually be acceptible as the printer will print the job that was sent to it. However, some printers require that the network connection be left open to report status.

If page count information is needed, the ifhp filter will then reopen the connection and get the page count information.

8.1. No Banner

Here is a typical printcap entry when banner printing is not wanted:

    lp:
      :sh
      :filter=/.../ifhp

The :sh (suppress headers or banners) explicitly disables banner printing, and the lpd server will not even attempt to print a banner.

8.2. Banner Printing and No OF Filter

This printcap entry specifies a banner generator program and and banner generation. There is no :of filter specified, so the banner is sent directly to the printer. In such a case the banner printing program should make sure that it generates output with the appropriate set of initialization strings. The pclbanner, psbanner, and lpbanner programs produce PCL, PostScript, and text banners suitable for a wide range of printers. The code for these banner generators is part of the LPRng distribution.

    lp:
      :bp=/.../pclbanner
      :of=/.../ifhp
      :filter=/.../ifhp
       # or
      :bp=/.../psbanner
      :of=/.../ifhp
      :filter=/.../ifhp
       # or
      :bp=/.../lpbanner
      :of=/.../ifhp
      :filter=/.../ifhp

8.3. Banner Printing With OF Filter

Finally, we may want banner printing together with the :of filter. This is usually the case when we need to perform special printer setups or require the ifhp filter to do accounting. In this case we need to make sure that the banner page is counted as part of the job:

    lp:
      :bp=/.../pclbanner or :bp=/.../psbanner or :bp=/.../lpbanner
      :of=/.../ifhp
      :filter=/.../ifhp

When invoked as an :of filter, the lpd server passes a -Fo option on the command line, so that the ifhp filter knows what mode it is operating in.

8.4. LPRng Options Controlling Banner Printing

The lpr -h (no header or banner) option suppresses putting banner name (L line) into the control file. The LPRng :ab (always banner) overrides this, and will print a banner using the user name information. The :sh (suppress header) option will override everything and prevent banners from being generated.

Banners are generated by the :bp=/... (banner program) program; different banners at start and end can be generated by using the :bs=/... (banner start) and :be=/... (banner end) options, which override the :bp= option.

8.5. of_options option

This option, usually used on the command line or in the printcap file as part of the :ifhp information, specifies a set of options to use when the filter is running in OF mode. For example:

    lp:
      :ifhp=sync@,pagecount@,waitend@,of_options=sync pagecount waitend
      :filter=/usr/local/libexec/filtes/ifhp
      :of=/usr/local/libexec/filtes/ifhp
    
    same as:
    
    lp:
      :filter=/usr/local/libexec/filtes/ifhp -Tsync@,pagecount@,waitend@
      :of=/usr/local/libexec/filtes/ifhp -Tsync,pagecount,waitend

In this printcap entry, the ifhp filter is invoked normally with the sync@, pagecount@ and waitend@ options. This causes it to send jobs as fast as possible to the output device and only monitor the device for error status. The of= entry causes the lpd print spooler to start ifhp in OF mode, and the of_options are used to override the other ones.

9.1. PCL Font Downloading

The following shows the a typical ifhp.conf file which has PCL font downloading enabled.

    #
    # Fonts and Font Downloading
    #  fontid is used to set the current font
    pcl_init=[ ... font ... ]
    
    # combination command
    pcl_font=[ delete_fonts font_id font_download font_primary ]
    
    # font control
    #
    font_op=0
    pcl_font_op=\033*c\%{font_op}F
    pcl_delete_fonts=\033*c0F
    
    font_id=1
    pcl_font_id=\033*c\%{font_id}D
    
    # set primary font
    font_primary=1
    pcl_font_primary=\033(\%{font_primary}X
    
    # font directory
    pcl_fontdir=/usr/local/lib/fonts
    
    #default font file
    font=c1201b.10

To allow users to download a font and have it set up for PCL use, the pcl_init option should include the font option in an appropriate position in the initialization sequence. As shown above, this will get expanded into the pcl_delete_fonts, pcl_font_id, pcl_font_download (which is has built-in support), and the pcl_font_primary options, which are expanded in order.

The pcl_font_download is supported by the builtin operation which will find the pcl_fontdir directory value and a value for the font variable, using values from the -Z and -T and configuration information in that order. If no font value is found, no font will be downloaded. For example:

    lpr -Tfont=font1,font2

When the pcl_font_download option is expanded, it will generate the pathnames /usr/local/lib/fonts/font1 and /usr/local/lib/fonts/font2, open these files, and send their contents directly to the printer.

9.2. PS Font Downloading

PostScript font downloading is supported in a similar manner to PCL font downloading.

    #
    # Fonts and Font Downloading
    #
    ps_init=[ ... font ... ]
    
    # combination command
    pcl_font=[ font_download ]
    
    # font directory
    ps_fontdir=/usr/local/lib/fonts
    
    #default font file
    font=font.ps.10

In a similar manner to the PCL font downloading, when the ps_init list is expanded, the ps_font entry will be expanded in turn. If the -Zfont=ZapDingbat.ps is specified, then the /usr/local/lib/fonts/ZapDingbat.sp file will be opened and downloaded to the printer.

9.3. PJL File Downloading

In a similar manner to the above font downloading, you can specify a configuration or other setup file that should be sent to the printer as part of the PJL setups. The following configuration shows how to set this up.

    #
    # PJL Initialization File Downloading
    #  fontid is used to set the current font
    pjl_init=[ ... setup  ... ]
    
    setup=initval
    font=\%s{setup}
    # setup directory
    pjl_fontdir=/usr/local/lib/fonts
    pjl_setup=[ font_download ]

The above configuration will cause the value of the setup -Z, -T or configuration option to be used.