NAME

	srv – server registry

SYNOPSIS

	bind –c #s$srvspec /srv /srv/clone /srv/id/... /srv/service1 /srv/service2 ...

DESCRIPTION

The srv device provides a tree of directories holding already–open channels to services. In effect, srv is a bulletin board on which processes may post open file descriptors to make them available to other processes. To install a channel, create a new file such as /srv/myserv and then write a text string (suitable for strtoul; see atof(2)) giving the file descriptor number of an open file. Any process may then open /srv/myserv to acquire another reference to the open file that was registered. An entry in srv holds a reference to the associated file even if no process has the file open. Removing the file from /srv releases that reference. 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. Opening the clone file allocates a new service directory. Reading clone returns the id of the new directory. This new service directory can then be accessed at /srv/id. Directories are recursive; each new service directory contains its own clone file and sub–directories. Directories can be walked from the root such as #s/id1/id2/id3 which makes them globally addressable. As a convention, /lib/namespace accepts the path to the service directory from the environment variable $srvspec, making it possible to start a new namespace using a specific service directory as a starting point.

EXAMPLE

To drop one end of a pipe into /srv, that is, to create a named pipe: 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"); At this point, any process may open and read /srv/namedpipe to receive the hello string. Data written to /srv/namedpipe can be received by executing read(p[1], buf, sizeof buf); in the above process. Create a disposable /srv and start a factotum(4) and a rio(1) in it. < [3]/srv/clone{ id=`{<[0=3]read} <[3=]@{ # close the clone fd rfork n bind –c /srv/$id /srv auth/factotum –s factotum rio } }

SOURCE

	/sys/src/9/port/devsrv.c