ref: dab168e6bd204c3cffae263d232051a47442c5ce
dir: /sys/man/3/0intro/
.TH INTRO 3 .SH NAME intro \- introduction to the Plan 9 devices .SH DESCRIPTION A Plan 9 .I device implements a file tree for client processes. A file name beginning with a pound sign, such as .LR #c , names the root of a file tree implemented by a particular .IR "kernel device driver" identified by the character after the pound sign. Such names are usually bound to conventional locations in the name space. For example, after .IP .EX bind("#c", "/dev", MREPL) .EE .LP an .IR ls (1) of .B /dev will list the files provided by the .I console device. .PP A kernel device driver is a .I server in the sense of the Plan 9 File Protocol, 9P (see Section 5), but with the messages implemented by local rather than remote procedure calls. Also, several of the messages .RI ( Nop , .IR Session , .IR Flush , and .IR Error ) have no subroutine equivalents. .PP When a system call is passed a file name beginning with .L "#" it looks at the next character, and if that is a valid .I device character it performs an .IR 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 .L "/" or end of string, those characters are passed as parameter .I aname to the attach. For example, .IP .EX #I2 .EE .PP identifies the number 2 IP protocol stack (see .IR ip (3)). .PP Each kernel device has a conventional place at which to be bound to the name space. The .I SYNOPSIS sections of the following pages includes a .I bind command to put the device in the conventional place. Most of these binds are done automatically by .IR init (8) using .B newns (see .IR auth (2)) on the file .B /lib/namespace (see .IR namespace (6)). When typed to .IR rc (1), the .I bind commands will need quotes to protect the .B # characters. .SH SEE ALSO .IR intro (5), .IR intro (2)