term% cat index.txt INTRO(3) Library Functions Manual INTRO(3)
NAME
intro - introduction to the Plan 9 devices
DESCRIPTION
A Plan 9 device implements a file tree for client processes. A file
name beginning with a pound sign, such as names the root of a file tree
implemented by a particular kernel device driver identified by the
character after the pound sign. Such names are usually bound to con‐
ventional locations in the name space. For example, after
bind("#c", "/dev", MREPL)
an ls(1) of /dev will list the files provided by the console device.
A kernel device driver is a server in the sense of the Plan 9 File Pro‐
tocol, 9P (see Section 5), but with the messages implemented by local
rather than remote procedure calls. Also, several of the messages
(Nop, Session, Flush, and Error) have no subroutine equivalents.
When a system call is passed a file name beginning with it looks at the
next character, and if that is a valid device character it performs an
attach(5) on the corresponding device to get a channel representing the
root of that device's file tree. If there are any characters after the
device character but before the next or end of string, those characters
are passed as parameter aname to the attach. For example,
#I2
identifies the number 2 IP protocol stack (see ip(3)).
Each kernel device has a conventional place at which to be bound to the
name space. The SYNOPSIS sections of the following pages includes a
bind command to put the device in the conventional place. Most of
these binds are done automatically by init(8) using newns (see auth(2))
on the file /lib/namespace (see namespace(6)). When typed to rc(1),
the bind commands will need quotes to protect the # characters.
SEE ALSO
intro(5), intro(2)
INTRO(3)