6  External Commands

External commands can be supported by yangcli-pro and yp-shell.

This support is limited to the functionality available to existing yangcli-pro commands:


6.1  YANG for Command Definitions

The YANG module definition is used for several tasks:


The YANG syntax is restricted for CLI command purposes:


Example command definition:



    rpc example-cmd {

      description "Example external command”;

      input {

        leaf parm1 {

          type string;

          description "The first example parameter";


        leaf parm2 {

          type int32;

          description "The second example parameter";






6.2  API Functions

There are a limited number of API functions available to add an external command.

A yangcli-pro or yp-shell command requires at least 3 components:

  1. YANG module “RPC statement” defining the command syntax

  2. Callback function to do the command when requested by user input

  3. Call to the registration function to add the command into the program


6.2.1  External Command Callback Function

The callback function for the external command must use the “yangcli_command_cbfn_t” definition in yangcli.h:



/* Callback template for a local command


 * Handles the command line for the specified command



 *   server_cb == server control block to use

 *   session_cb == session control block to use

 *   rpc == object template for the command

 *   line == input command line to execute

 *   len == offset into the line to start processing

 *          this can be > 0 if the command is the left-hand-side

 *          of an assignment statement


 *    status


typedef status_t

    (*yangcli_command_cbfn_t) (server_cb_t *server_cb,

                               session_cb_t *session_cb,

                               obj_template_t *rpc,

                               const xmlChar *line,

                               uint32 len);



The following example callback can be found in example-fan.cpp




 * FUNCTION do_example_cmd (local RPC)


 * Do Example Command



 *    server_cb == server control block to use

 *    session_cb == session control block to use

 *    rpc == RPC method for the example-cmd command

 *    line == CLI input in progress

 *    len == offset into line buffer to start parsing



 *   status


static status_t

    do_example_cmd (server_cb_t *server_cb,

                    session_cb_t *session_cb,

                    obj_template_t *rpc,

                    const xmlChar *line,

                    uint32 len)




    status_t res = NO_ERR;

    val_value_t *valset =

        get_valset(server_cb, session_cb, rpc, &line[len], &res);

    if (valset && (res == NO_ERR)) {

        val_value_t *parm1 =

            val_find_child(valset, MODNAME, (const xmlChar *)"parm1");

        if (parm1) {

            log_debug("\nGot parm1=%s", VAL_STR(parm1));



        val_value_t *parm2 =

            val_find_child(valset, MODNAME, (const xmlChar *)"parm2");

        if (parm2) {

            log_debug("\nGot parm2=%d", VAL_INT32(parm2));



        /* do something with the parameters */





    return res;


}  /* do_example_cmd */




Key steps:


6.2.2  Register an External Command

The “register_command” function is called from the yp_show_init function to register an external command:




* FUNCTION register_command



*    server_cb == server control block to use

*    module == module name containing the RPC method

*    ycli_command_name == RPC method name

*    command_fn == pointer to callback function for this command

*    is_top_cmd == TRUE if opt-level command

*    yangcli_ok == TRUE if OK for yangcli to use it

*    ypshell_ok == TRUE if OK for yp-shell to use it

*    ypserver_ok == TRUE if OK for yp-server to use it



*    status of the operation


extern status_t

    register_command (

              server_cb_t *server_cb,

              const xmlChar *module,

              const xmlChar *ycli_command_name,

              yangcli_command_cbfn_t command_fn,

              boolean is_top_cmd,

              boolean yangcli_ok,

              boolean ypshell_ok,

              boolean ypserver_ok);


Usage Example: (from example-fan.cpp)



        server_cb_t *server_cb = get_default_server_cb();

        if (server_cb == NULL){

            res = ERR_NCX_NOT_FOUND;

        } else {

            res = register_command(server_cb,


                                   (const xmlChar *)"example-cmd",


                                   TRUE,   // is_top_cmd

                                   TRUE,   // yangcli_ok

                                   TRUE,   // ypshell_ok

                                   FALSE); // ypserver_ok (not used)




Usage Notes: