ref: b868b9919f570cbcbdb3c713bf1431b9d843ea43
dir: /sys/man/3/srv/
.TH SRV 3 .SH NAME srv \- server registry .SH SYNOPSIS .nf .BI "bind -c #s" $srvspec " /srv" .BI /srv/ clone .BI /srv/ id / ... .BI /srv/ service1 .BI /srv/ service2 .I ... .fi .SH DESCRIPTION The .I srv device provides a tree of directories holding already-open channels to services. In effect, .I srv is a bulletin board on which processes may post open file descriptors to make them available to other processes. .PP To install a channel, create a new file such as .BI /srv/ myserv and then write a text string (suitable for .IR strtoul ; see .IR atof (2)) giving the file descriptor number of an open file. Any process may then open .BI /srv/ myserv to acquire another reference to the open file that was registered. .PP An entry in .I srv holds a reference to the associated file even if no process has the file open. Removing the file from .B /srv releases that reference. .PP It is an error to write more than one number into a server file, or to create a file with a name that is already being used. .PP Opening the .I clone file allocates a new service directory. Reading .I clone returns the .I id of the new directory. This new service directory can then be accessed at .BI /srv/ id . Directories are recursive; each new service directory contains its own .I clone file and sub-directories. Directories can be walked from the root such as .BI #s/ id1 / id2 / id3 which makes them globally addressable. As a convention, .B /lib/namespace accepts the path to the service directory from the environment variable .IR $srvspec , making it possible to start a new namespace using a specific service directory as a starting point. .SH EXAMPLE To drop one end of a pipe into .BR /srv , that is, to create a named pipe: .IP .EX int fd, p[2]; char buf[32]; pipe(p); fd = create("/srv/namedpipe", OWRITE, 0666); fprint(fd, "%d", p[0]); close(fd); close(p[0]); fprint(p[1], "hello"); .EE .PP At this point, any process may open and read .B /srv/namedpipe to receive the .B hello string. Data written to .B /srv/namedpipe can be received by executing .IP .EX read(p[1], buf, sizeof buf); .EE .PP in the above process. .PP Create a disposable .B /srv and start a .IR factotum (4) and a .IR rio (1) in it. .IP .EX <[3]/srv/clone{ id=`{<[0=3]read} <[3=]@{ # close the clone fd rfork n bind -c /srv/$id /srv auth/factotum -s factotum rio } } .EE .PP .SH SOURCE .B /sys/src/9/port/devsrv.c