[systemd-devel] [RFC] xyzctl-common

[Zbigniew Jędrzejewski-Szmek]

On Sat, Nov 16, 2013 at 07:41:13PM +0100, Peeters Simon wrote:
> hello all,
> 
> During the sd_bus porting I noted that the *ctl tools (and
> systemd-analyze) contain a lot of common boilerplate code.
> 
> So the basic idea is to split this boilerplate out into
> xyzctl-common.[ch] so that f.ex the bottom hostnamectl.c would look
> like:
> 
> ...
> static void help(void ) {...}
> 
> enum {
>         ARG_TRANSIENT = 0x100,
>         ARG_STATIC,
>         ARG_PRETTY,
> };
> 
> static int parse_arg(int option, const char* arg) {
>         assert(option >= 0);
> 
>         switch (option) {
>                 case ARG_TRANSIENT:
>                         arg_transient = true;
>                         break;
> 
>                 case ARG_PRETTY:
>                         arg_pretty = true;
>                         break;
> 
>                 case ARG_STATIC:
>                         arg_static = true;
>                         break;
> 
>                 default:
>                         return -EINVAL;
>         }
> 
>         return 1;
> }
> 
> int main(int argc, char *argv[]) {
> 
>         static const struct option options[] = {
>                 { "transient", no_argument, NULL, ARG_TRANSIENT },
>                 { "static",    no_argument, NULL, ARG_STATIC    },
>                 { "pretty",    no_argument, NULL, ARG_PRETTY    },
>                 {}
>         };
>         static const xyzctl_verb verbs[] = {
>                 { "status",        LESS,  1, show_status,   XYZCTL_USE_PAGER  },
>                 { "set-hostname",  EQUAL, 2, set_hostname,  XYZCTL_USE_POLKIT },
>                 { "set-icon-name", EQUAL, 2, set_icon_name, XYZCTL_USE_POLKIT },
>                 { "set-chassis",   EQUAL, 2, set_chassis,   XYZCTL_USE_POLKIT },
>                 {}
>         };
>         static const xyzctl_tool hostnamectl = {
>                 &help,
>                 &parse_arg,
>                 XYZCTL_NO_USER,
>                 options,
>                 verbs
>         };
> 
>         return xyzctl_main(&hostnamectl, argc, argv);
> }
> 
> it would use or-able flags to controll common functionality, i currently have:
>         enum verb_flags {
>                 XYZCTL_NO_BUS = 1,
> The execution of the verb does not require a bus connection.
> The system will try to connect to the bus, but will ignore any errors,
> and pass a NULL bus.
>                 XYZCTL_USE_PAGER = 2,
> Open a pager unless the user passes --no-pager
>                 XYZCTL_USE_POLKIT = 4,
> Starts the polkit agent unless the user passes --no-ask-password
>                 XYZCTL_LOOP_ARGS = 8,
> Executes the verb once for each argument.
> This is usefull where
>   $ xyzctl verb a b c
> is the same as
>   $ xyzctl verb a
>   $ xyzctl verb b
>   $ xyzctl verb c
I think that we do some sorting on the arguments and other operations
which mean that the behaviour for multiple args isn't usually
*exactly* the same as for one repeated. What exactly does this
flag mean?

>         };
> 
>         enum tool_flags {
>                 XYZCTL_NO_REMOTE = 1,
> Do not allow the use of --host=HOST to connect to a remote host
>                 XYZCTL_NO_MACHINE = 2,
> Do not allow the use of --machine=CONTAINER to connect to a container
>                 XYZCTL_NO_USER = 4,
> Do not allow connection to the user bus by using --user
>                 XYZCTL_CONNECT_SYSTEMD = 8,
> connect directly to systemd's private socket.
>         }
> 
> 
> As a proof of concept I ported hostnemctl and loginctl resulting in +-
> 360 lines less code
> 
> 
> Does anybody have any comments on the basic idea and/or the proposed interface?

If it makes things shorter, without making them much more complicated,
then it's probably a good idea. Can you post the full patch for 
loginctl and hostnamectl?

Zbyszek