One- and two-bit deep icons are stored as text, one line of the file to one scan line of display. Each line is divided into 8-bit, 16-bit, or 32-bit big-endian words, stored as a list of comma-separated hexadecimal C constants, such as:
This odd format is historical and the programs that read it are somewhat forgiving about blanks and the need for commas.
The files lib/face/*/.dict hold a correspondence between users at machines and face files. The format is
The machine is the domain name of the machine sending the message, and user the name of the user sending it. The directory is a further subdirectory of (say) /lib/face/48x48x1, named by a single letter corresponding to the first character of the user names. The file is the name of the file, typically but not always the user name, and ver is a number to distinguish different images, for example to distinguish the image for Bill Gates from the image for Bill Joy, both of which might otherwise be called b/bill. For example, Bill Gates might be represented by the line
If multiple entries exist for a user in the various .dict files, faces chooses the highest pixel size less than or equal to that of the display on which it is running.
Finally, or rather firstly, the file /lib/face/.machinelist contains a list of machine/domain pairs, one per line, to map any of a set of machines to a single domain name to be looked up in the .dict files. The machine name may be a regular expression, so for example the entry
maps any of the machines in Bell Labs Research into the shorthand name astro, which then appears as a domain name in the .dict files.