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

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

> 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 :-)
> 
> /Bruce

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