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

["Wiles, Roger Keith" <keith.wiles@windriver.com>]

> On Nov 3, 2014, at 8:16 AM, Bruce Richardson <bruce.richardson@intel.com> wrote:
> 
> 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?

I guess that would be reasonable, but then I would have to add support for all of the command line parsing being done in the cmdline code. Think of this as a default case for the parser and to me that makes more sense then just doing my own command line design. In the cmdline code you guys provided is a lot of features like history, control key support, arg parsing (IP, MAC) and many others. I would rather not have to write that code myself.

The default case is the same behavior today, with giving a no match error unless they add the external parser.
> 
> /Bruce

Keith Wiles, Principal Technologist with CTO office, Wind River mobile 972-213-5533