Re: [dpdk-dev] [PATCH] Add external parser support for unknown commands.

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, Nov 03, 2014 at 02:08:46PM +0000, Wiles, Roger Keith wrote:
> 
> > On Nov 3, 2014, at 4:41 AM, Bruce Richardson <bruce.richardson@intel.com> wrote:
> >
> > On Sun, Nov 02, 2014 at 04:28:28PM -0600, Keith Wiles wrote:
> >> Allow for a external parser to handle the command line if the
> >> command is not found and the developer has called the routine
> >> int cmdline_set_external_parser(struct cmdline * cl,
> >>                                cmdline_external_parser_t parser);
> >> function to set the function pointer.
> >>
> >> The function for the external parser function should return CMDLINE_PARSE_NOMATCH
> >> if not able to match the command requested or zero is handled.
> >>
> >> Prototype of external routine:
> >> int (*cmdline_external_parser_t)(struct cmdline * cl, const char * buy);
> >>
> >> Signed-off-by: Keith Wiles <keith.wiles@windriver.com>
> >
> > Hi Keith,
> >
> > what is the expected use case for this? Is it for embedding other programming languages alongside the existing DPDK command-line or some other purpose? [Perhaps the use case could be called out in the patch description]
> 
> Hi Bruce,
> 
> I guess the external parser could be used for other programming languages, but the case I was looking at was to provide a default escape from the command line parser to allow my application to handle the commands not understood by the parser. Now that you point it out I could use something like ‘%<line-of-script-code>’ to execute a single line of script code, which is a good idea (thanks).
> 
> One case I am looking at is when you want to execute a command and do not want to add the support into the commands.c file for every possible command. Take the case where you have a bunch of scripts (Lua) in a directory much like a bin directory. Then you could type foo.lua or foo on the command line and execute the foo.lua having the application detect you want to load and run a Lua script after it has finished parsing for the builtin commands.
> 
> For Pktgen I had to add a command called ‘run <filename> <args…>’ to support running a script with arguments. I also needed to add a argvlist type to cmdline to not error out on that command and split up the args into a argv list like format. (Maybe I need to submit that code??) It seemed more straight forward to just pass the command line to the application to run the command. I understand that seems like a minor point, but it does make it easier to use and to support the features I want to support in my PoC.
> 
> Using this method you can just type the name instead of something like ‘run foo.lua’ or just ‘run foo’ and let the code figure out what to run. I have more plans for this features as well and have not finished the basic PoC yet. If you want a peek I can show you what I am working on currently.
> 
> Does this help and do I really need to add all of this to the commit message :-)
>
Thanks for the explanation. However, if you are looking to have the application handle a bunch of commands itself, why does it need to use the commandline library at all? Why not just have the app handle all the commands instead of some of them?

/Bruce