srv – server registry

bind #s /srv

The srv device provides a one–level directory 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.

To drop one end of a pipe into /srv, that is, to create a named pipe:
int fd, p[2];
char buf[32];
fd = create("/srv/namedpipe", OWRITE, 0666);
fprint(fd, "%d", 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.

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