LPRng-HOWTO: 15 Oct 2001 (For LPRng-3.7.9)
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# 13.3. Spool Control File

- `spool_control_file` spool queue control file - default control.%P

The spool control file is used to control the operations of the spooler, and is in the spool or control directory. The file name specified by the `queue_control_file` option (default `control.%P` - the %P is expanded to the print queue name); in our example, the control file would be: `/var/lpd/pr/control.pr`.

The lpc program sends spool control requests to the lpd daemon, which updates the control file and then signals the appropriate spool server processes that an update has been performed. The control file contents have the form:

        key value

The following keys and their values are currently supported.

Key | Value | Purpose
--- | --- | ---
`printing_disabled` | 0 or 1 | disable printing of jobs in queue
`spooling_disabled` | 0 or 1 | disable placing jobs in queue
`holdall` | 0 or 1 | hold jobs until released
`redirect` | `printer` | transfer jobs to indicated printer
`class` | `glob expression` | print only jobs whose class matches glob expression
`server_order` | `printer name list` | preferred order of printer use
`debug` | `debugging options` | debugging and tracing

The `printing_disabled` and `spooling_disabled` are managed using the `lpc start`, `lpc stop`, `lpc enable` and `lpc disable` commands. Similarly, `holdall` is enabled and disabled by `holdall` and `noholdall` commands respectively. When holdall is enabled, jobs placed in the print queue will be held until they are explicitly released for printing by an `lpc release` command.

The `redirect` entry is used to redirect or transfer jobs which are spooled to this queue to another queue, and is managed by the redirect command. The `lpc redirect off` removes the redirect entry from the control file.

The `class` entry is similar in operation to the `holdall`, but allows jobs whose class identification matches the glob expression to be printed. This can be useful when you have special forms or paper required for a print job, and want to run only these jobs when the paper is in the printer.

The `server_order` entry is created and updated for a multiple printer queue. It records the order in which printers should next be used for normal print operations. This allows round robin use of printers, rather than having all jobs printed to the first printer in the list of printers.

The `debug` entry is set by the `lpc debug` command, and is used to enable or disable debugging and tracing information for a spool queue. This facility is for diagnostic purposes only.

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