/** @page primercommand Command Development Primer This page provides a primer for writing commands by introducing @c hello module. The full source code used in this example can be found in hello.c, and the @ref primercmdcode section shows how to use it. A summary of this information can be found in @ref helpercommand . @section primercmdhandler Command Handlers Defining new commands and their helpers is easy. The following code defines a simple command handler that delegates its argument parsing: @code COMMAND_HANDLER(handle_hello_command) { const char *sep, *name; int retval = CALL_COMMAND_HANDLER(handle_hello_args); if (ERROR_OK == retval) command_print(CMD_CTX, "Greetings%s%s!", sep, name); return retval; } @endcode Here, the @c COMMAND_HANDLER macro establishes the function signature, see in command.h by the @c __COMMAND_HANDLER macro. The COMMAND_HELPER macro function allows defining functions with an extended version of the base signature. These helper functions can be called (with the appropriate parameters), the @c CALL_COMMAND_HANDLER macro to pass any e as parameters to the following helper function: The subsequent blocks of code are a normal C function that can do anything, so only complex commands deserve should use comamnd helper functions. In this respect, this example uses one to demonstrate how -- not when -- they should be used. @code static COMMAND_HELPER(handle_hello_args, const char **sep, const char **name) { if (argc > 1) { LOG_ERROR("%s: too many arguments", CMD_NAME); return ERROR_COMMAND_SYNTAX_ERROR; } if (1 == CMD_ARGC) { *sep = ", "; *name = CMD_ARGV[0]; } else *sep = *name = ""; return ERROR_OK; } @endcode Of course, you may also call other macros or functions, but that extends beyond the scope of this tutorial on writing commands. @section primercmdreg Command Registration Before this new function can be used, it must be registered somehow. For a new module, registering should be done in a new function for the purpose, which must be called from @c openocd.c: @code static const struct command_registration hello_command_handlers[] = { { .name = "hello", .mode = COMMAND_ANY, .handler = &handle_hello_command, .help = "print a warm greetings", .usage = "[]", }, { .chain = foo_command_handlers, } COMMAND_REGISTRATION_DONE }; int hello_register_commands(struct command_context_s *cmd_ctx) { return register_commands(cmd_ctx, NULL, handle_command_handlers); } @endcode That's it! The command should now be registered and avaiable to scripts. @section primercmdchain Command Chaining This example also shows how to chain command handler registration, so your modules can "inherit" commands provided by other (sub)modules. Here, the hello module includes the foo commands in the same context that the 'hello' command will be registered. If the @c chain field had been put in the 'hello' command, then the @c foo module commands would be registered under it. Indeed, that technique is used to define the 'foo bar' and 'foo baz' commands, as well as for the example drivers that use these modules. The code for the 'foo' command handlers can be found in @c hello.c. @section primercmdcode Trying These Example Commands These commands have been inherited by the dummy interface, faux flash, and testee target drivers. The easiest way to test these is by using the dummy interface. Once OpenOCD has been built with this example code, the following command demonstrates the abilities that the @c hello module provides: @code openocd -c 'interface dummy' \ -c 'dummy hello' \ -c 'dummy hello World' \ -c 'dummy hello {John Doe}' \ -c 'dummy hello John Doe' # error: too many arguments @endcode If saved in @c hello.cfg, then running openocd -f hello.cfg should produce the following output before displaying the help text and exiting: @code Greetings! Greetings, World! Greetings, John Doe! Error: hello: too many arguments Runtime error, file "openocd.cfg", line 14: hello: too many arguments dummy hello [] prints a warm welcome @endcode */