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The content-type attribute is defined with the -I content-type-list option of the lpadmin command. Most printers can print files of two types: the same type as the printer type (if the printer type is defined) and the type simple (meaning an ASCII file), which is the default content type for all printers.
Files of content type simple are assumed to contain only two types of characters, printable ASCII characters and the following control characters:
The word ``carriage'' may be archaic for modern laser printers, but these printers do actions similar to those done by a carriage. If a printer can handle several types of files, including simple, you must include simple explicitly in the content type list. If you do not want a printer to accept files of type simple, specify a blank content-type-list (-I "") on the lpadmin command line. Some printers, though, can accept (and print properly) several different types of files. When adding this kind of printer, specify the names of the content types the new printer accepts by adding these names to the list. (By default, the list contains only one type: simple.) If you're adding a remote printer, list the content types that have been established for it by the administrator of the system on which it resides.
The content-type-list is a list of names separated by commas or spaces. If you use spaces to separate the names, enclose the entire list (but not the -I) in quotes.
Content type names may look like printer type names, but you are free to choose names that are meaningful to you and the people using the printer. (The names simple and any are recognized as having particular meanings by the print service; be sure to use them consistently. The name terminfo is also reserved, as a reference to all types of printers.) The names must contain no more than 14 characters and may include only letters, digits, and underscores. The following table lists and describes some accepted content types.
Commonly-used content types
| Types | Description |
|---|---|
| troff | Device-independent output from troff (troff filters are available in the Advanced Commands package) |
| otroff | CAT typesetter instructions generated by BSD or pre-System V troff (old troff) |
| daisy | Print files intended for a Diablo 630 (``daisy-wheel'') printer |
| dmd | Print the contents of a bit-mapped display from a terminal |
| tek4014 | Print files formatted for a Tektronix 4014 device |
| tex | DVI format files |
| plot | Plotting instructions for Tektronix displays and devices |
| raster | Raster bitmap format for Varian raster devices |
| cif | Output of BSD cifpbt |
| fortran | ASA carriage control format |
| postscript | PostScript language |
| pcl | HP LaserJet native output format |
| simple | ASCII file |
When a file is submitted to the print service for printing with the printer specified by the -d any option of the lp command, the Print Service searches for a printer capable of handling the job. The Print Service can identify an appropriate printer through either the content type name or the printer type name. Therefore, you may specify either name (or no name) when submitting a file for printing. If the same content type is printable by several different types of printers, use the same content type names when you add those printers. This makes it easier for the people using the printers because they can use the same name to identify the type of file they want printed regardless of the printing destination.
Most manufacturers produce printers that accept simple ASCII files. While these printers are different types (and thus have different initialization control sequences), they may all be capable of handling the same type of file, which we call simple. Several manufacturers may produce printers that accept ANSI X3.64 defined escape sequences. However, the printers may not support all the ANSI capabilities; they may support different sets of capabilities. You may want to differentiate them by assigning different content type names for these printers.
While it may be desirable to list content types for each printer, it is not always necessary. If you don't, the printer type will be used as the name of the content type the printer can handle. If you have not specified a printer type, the print service will assume the printer can print only files of content type simple. This may be sufficient if you require users to specify the proper printer explicitly and if files are properly prepared for the printer before being submitted for printing.