userv options [--] service-user service-name [argument ...] userv options -B|--builtin [--] builtin-service [info-argument ...]
service-user specifies which user is to provide the service.
The user may be a login name or a numeric uid, or -
to indicate
that the service user is to be the same as the calling user.
The service name is interpreted by the userv[1] daemon on behalf of the service user. It will often be the name of a program.
-B
--builtin
-
(indicating the
calling user).If the builtin service being requested requires a service-argument then this must be supplied to the client in the same argument as the builtin-service. See Directives for changing execution settings, subsection 4.2.4 for details of the builtin services available, and Security-overriding options, section 2.2 for details of the --override options.
The actual service name passed will be the builtin-service; note that this actual service name (as opposed to the override data) and the info-arguments supplied will be ignored by most builtin services; the override mechanism and execute-builtin will be used to ensure that the right builtin service is called with the right service-arguments.
-f
fd[
modifiers]=
filename
--file
fd[
modifiers]=
filename
The descriptor in the service program that should be connected must be
specified as fd, either as a decimal number or as one of the
strings stdin
, stdout
or stderr
. The next argument is
a filename which will be opened by the client with the privileges of
the calling user.
modifiers is used to specify whether the file or descriptor is to be read from or written to. It consists of a series of words separated by commas. A comma may separate the modifiers from the fd and is required if fd is not numeric.
The modifier words are:
read
O_RDONLY
: Allow reading and not writing. May not be used with
write
or things that imply it.
write
O_WRONLY
: Allow writing and not reading. Doesn't truncate or
create without truncate
or create
. write
or things
that imply it may not be used with read
.
overwrite
write,create,truncate
.
create
creat
O_CREAT
: Creates the file if necessary. Implies write
.
exclusive
excl
O_EXCL
: Fails if the file already exists. Implies write
and
create
. May not be used with truncate
.
truncate
trunc
O_TRUNC
: Truncate any existing file. Implies write
.
May not be used with exclusive
.
append
O_APPEND
: All writes will append to the file. Implies write
(but not create
).
sync
O_SYNC
: Do writes synchronously. Implies write
.
wait
nowait
close
fd
read
and write
must be specified, and no
other words are allowed. The filename may also be stdin
,
stdout
or stderr
for file descriptor 0, 1 or 2 respectively.
If no modifiers which imply read
or write
are used it
is as if write
had been specified, except that if the
filedescriptor 0 of the service is being opened (either specified
numerically or with stdin
) it is as if overwrite
had been
specified (or write
if only fd
was specified).
The client will also use O_NOCTTY
when opening files specified by
the caller, to avoid changing its controlling terminal.
By default stdin, stdout and stderr of the service will be connected to the corresponding descriptors on the client. Diagnostics from the client and daemon will also appear on stderr.
If wait
is specified, the client will wait for the pipe to be
closed, and only exit after this has happened. This means that either
the receiving end of the pipe connection was closed while data was
still available at the sending end, or that the end of file was
reached on the reading file descriptor. Errors encountered reading or
writing in the client at this stage will be considered a system error
and cause the client to exit with status 255, but will not cause
disconnection at the service side since the service has already
exited.
If close
is specified the client will immediately close the pipe
connection by killing the relevant copy of cat. If the service
uses the descriptor it will get SIGPIPE (or EPIPE) for a
writing descriptor or end of file for a reading one; the descriptor
opened by or passed to the client will also be closed.
If nowait
is specified then the client will not wait and the
connection will remain open after the client terminates. Data may
continue to be passed between the inheritors of the relevant
descriptor on the service side and the corresponding file or
descriptor on the client side until either side closes their
descriptor. This should not usually be specified for stderr (or
stdout if --signals stdout
is used) since diagnostics from
the service side may arrive after the client has exited and be
confused with expected output.
The default is wait
for writing file descriptors and close
for reading ones.
-w
fd=
action
--fdwait
fd=
action
wait
, nowait
or close
as described above. The file descriptor must be specified as open
when this option is encountered; this option is overridden by any
later --file or --fdwait option - even by a
--file which does not specify an action on termination (in this
case the default will be used, as described above).
-D
name=
value
--defvar
name=
value
u-
name
and are passed to the
service in environment variables USERV_U_
name
. name
may contain only alphanumerics and underscores, and must start with a
letter. If several definitions are given for the same name then
only the last is effective.
-t
seconds
--timeout
seconds
-S
method--signals
methodThe method may be one of the following:
number
number-nocore
number
is used rather than
number-nocore
then 128 will be added if the service dumped core.
number
is very like the exit code mangling done by the Bourne
shell.
highbit
stdout
Problems such as client usage errors, the service not being found or permission being denied or failure of a system call are system errors. An error message describing the problem will be printed on the client's stderr, and the client's exit status will be 255. If the client dies due to a signal this should be treated as a serious system error.
-H
--hidecwd
-P
--sigpipe
stdout
is in use.
-h
--help
--copyright
-h
or --help
prints the client's usage message;
--copyright
prints the copyright and lack of warranty notice.
--override
configuration-data
--override-file
filename
--spoof-user
user
--spoof-user
option will not affect which user is chosen if
the service user is specified as just -
; in this case the service
user will be the real calling user.