Srv
converts between file system operations by applications
and messages on channels, as described in
sys-file2chan(2).
Each attach that does not include a
spec
produces a new instance: an empty directory owned
by the current user in which only files
may be created, and then only by
sys-file2chan,
using a special internal interface.
Each such file initially has the same owner as the
directory, and permissions
8r600
(read-write for the owner only),
but the permissions can be changed by
Sys->wstat
(see
sys-stat(2))
and thus
chmod(1).
If mode
Sys->DMEXCL
is thereby set, the file becomes exclusive-use and can be opened by
only one process at a time.
The file length and
mode bit
Sys->DMAPPEND
may also be set by
wstat
but are not interpreted by the system.
Files may be removed, directly using
sys-remove(2)
(and thus
rm(1)),
or indirectly by opening them with mode
Sys->ORCLOSE
(see
sys-open(2)).
File2chan
also removes the corresponding file when the last references
to the server's read and write channels have gone
(eg, on server exit).
A
spec
may be given to name specific instances of
srv,
so that a new name space can bind in a service created in another.
Only the owner (original creator) of the instance may attach to it,
unless the mode of the service directory is changed
using
Sys->wstat
(see
sys-stat(2))
to have general access.