manvolnum — A reference volume number
manvolnum ::=
(text | phrase
db._phrase | replaceable
| Graphic inlines | Indexing inlines | Linking inlines | Ubiquitous inlines)*
In a DocBook reference page, the manvolnum
holds the number of the volume in which the refentry
belongs.
The notion of a volume number is historical.
UNIX manual pages (“man pages”), for
which refentry
was devised, were typically stored in
three-ring binders. Each bound manual was a volume in a set and
contained information about a particular class of things. For example,
volume 1 was for user commands, and volume 8 was for administrator
commands.
Volume numbers need not be strictly numerical; volume “l” frequently held manual pages for local additions to the system, and the X Window System manual pages had an “x” in the volume number: for example, 1x.