Shell

Simple shell interpreter More...

Detailed Description

Simple shell interpreter

Security expectations

Access to the shell grants access to the system that may exercise any power the firmware can exercise. While some commands only provide limited access to the system, and it is best practice for commands to validate their input, there is no expectation of security of the system when an attacker gains access to the shell.

Usage

Enable the shell module e.g. by adding the following snippet to your applications Makefile.

USEMODULE += shell

And run the shell using shell_run_forever e.g. from the main thread after everything is set up. This call will never return.

Builtin Commands

The commands help and help_json are builtins that print the list of available commands: The former prints a human readable table and is always available, the latter requires module shell_builtin_cmd_help_json to be used and will give the same info machine readable.

Topics
	Shell commands
	Shell compile time configurations

Files
file	shell.h
	Shell interface definition.

Data Structures
struct	shell_command_t
	A single command in the list of the supported commands. More...
struct	shell_command_xfa_t
	A single command in the list of the supported commands. More...

Macros
#define	SHELL_DEFAULT_BUFSIZE   (128)
	Default shell buffer size (maximum line length shell can handle)
#define	SHELL_COMMAND(cmd, help, func)
	Define shell command.

Typedefs
typedef int(*	shell_command_handler_t) (int argc, char **argv)
	Prototype of a shell callback handler.
typedef struct shell_command_t	shell_command_t
	A single command in the list of the supported commands.

Functions
void	shell_post_readline_hook (void)
	Optional hook after readline has triggered.
void	shell_pre_command_hook (int argc, char **argv)
	Optional hook before shell command is called.
void	shell_post_command_hook (int ret, int argc, char **argv)
	Optional hook after shell command is called.
void	shell_run_once (const shell_command_t *commands, char *line_buf, int len)
	Start a shell and exit once EOF is reached.
static void	shell_run_forever (const shell_command_t *commands, char *line_buf, int len)
	Start a shell and restart it if it exits.
static void	shell_run (const shell_command_t *commands, char *line_buf, int len)
	Back-porting alias for shell_run_forever.
int	shell_handle_input_line (const shell_command_t *commands, char *line)
	Parse and run a line of text as a shell command with arguments.
int	shell_parse_file (const shell_command_t *commands, const char *filename, unsigned *line_nr)
	Read shell commands from a file and run them.

Macro Definition Documentation

SHELL_COMMAND

#define SHELL_COMMAND	(		cmd,
			help,
			func )

Value:

    XFA_USE_CONST(shell_command_xfa_t, shell_commands_xfa_v2); \
    static FLASH_ATTR const char _xfa_ ## cmd ## _cmd_name[] = #cmd; \
    static FLASH_ATTR const char _xfa_ ## cmd ## _cmd_desc[] = help; \
    XFA_CONST(shell_command_xfa_t, shell_commands_xfa_v2, 0) _xfa_ ## cmd ## _cmd = { \
        .name = _xfa_ ## cmd ## _cmd_name, \
        .desc = _xfa_ ## cmd ## _cmd_desc, \
        .handler = &func \
    };

Define shell command.

Note

This is not available from C++, but a trivial C file can easily hook up a extern "C" function implemented in C++.

This macro is a helper for defining a shell command and adding it to the shell commands XFA (cross file array).

Shell commands added using this macros will be sorted after builtins and commands passed via parameter to shell_run_once(). If a command with the same name exists in any of those, they will make a command added via this macro inaccassible.

Commands added with this macro will be sorted alphanumerically by name.

Warning

This feature is experimental!
This should be considered experimental API, subject to change without notice!

Example:

#include "shell.h"
static int _my_command(int argc, char **argv) {
  // ...
}
SHELL_COMMAND(my_command, "my command help text", _my_command);

Definition at line 304 of file shell.h.

SHELL_DEFAULT_BUFSIZE

#define SHELL_DEFAULT_BUFSIZE   (128)

Default shell buffer size (maximum line length shell can handle)

Warning

When terminals that buffer input and send the full command line in one go are used on stdin implementations with fast bursts of data, it may be necessary to increase the STDIO_RX_BUFSIZE to make practical use of this buffer, especially because the current mechanism of passing stdin (isrpipe_t stdin_isrpipe) does not support backpressure and overflows silently. As a consequence, commands through such terminals appear to be truncated at STDIO_RX_BUFSIZE bytes (defaulting to 64) unless the command is sent in parts (on many terminals, by pressing Ctrl-D half way through the command).

For example, this affects systems with direct USB stdio (STDIO over CDC ACM (usbus)) with the default terminal pyterm.

Definition at line 119 of file shell.h.

Typedef Documentation

shell_command_handler_t

typedef int(* shell_command_handler_t) (int argc, char **argv)

Prototype of a shell callback handler.

The functions supplied to shell_run() must use this signature. It is designed to mimic the function signature of main(). For this reason, the argument list is terminated with a NULL, i.e argv[argc] == NULL (which is an ANSI-C requirement, and a detail that newlib's getopt() implementation relies on). The function name is passed in argv[0].

Escape sequences are removed before the function is called.

The called function may edit argv and the contained strings, but it must be taken care of not to leave the boundaries of the array. This functionality is another property that many getopt() implementations rely on to provide their so-called "permute" feature extension.

Parameters

[in]	argc	Number of arguments supplied to the function invocation.
[in]	argv	The supplied argument list.

Returns

0 on success

Anything else on failure

Definition at line 176 of file shell.h.

shell_command_t

typedef struct shell_command_t shell_command_t

A single command in the list of the supported commands.

The list of commands is NULL terminated, i.e. the last element must be { NULL, NULL, NULL }.

Function Documentation

shell_handle_input_line()

int shell_handle_input_line	(	const shell_command_t *	commands,
		char *	line )

Parse and run a line of text as a shell command with arguments.

Parameters

[in]	commands	ptr to array of command structs
[in]	line	The input line to parse

Returns

return value of the found command

-ENOEXEC if no valid command could be found

shell_parse_file()

int shell_parse_file	(	const shell_command_t *	commands,
		const char *	filename,
		unsigned *	line_nr )

Read shell commands from a file and run them.

Note

This requires the vfs module.

Parameters

[in]	commands	ptr to array of command structs
[in]	filename	file to read shell commands from
[out]	line_nr	line on which an error occurred, may be NULL

Returns

0 if all commands were executed successful error return of failed command otherwise

shell_post_command_hook()

void shell_post_command_hook	(	int	ret,
		int	argc,
		char **	argv )

Optional hook after shell command is called.

User implemented function gets called before a valid shell command will be called.

Note

Only executed with the shell_hooks module.

Parameters

[in]	ret	Return value of the shell command.
[in]	argc	Number of arguments supplied to the function invocation.
[in]	argv	The supplied argument list.

shell_post_readline_hook()

void shell_post_readline_hook

(

void

)

Optional hook after readline has triggered.

User implemented function gets called after the shell readline is complete.

Note

Only executed with the shell_hooks module.

shell_pre_command_hook()

void shell_pre_command_hook	(	int	argc,
		char **	argv )

Optional hook before shell command is called.

User implemented function gets called before a valid shell command will be called.

Note

Only executed with the shell_hooks module.

Parameters

[in]	argc	Number of arguments supplied to the function invocation.
[in]	argv	The supplied argument list.

shell_run()

static void shell_run ( const shell_command_t * commands, char * line_buf, int len )

inlinestatic

Back-porting alias for shell_run_forever.

Parameters

[in]	commands	ptr to array of command structs
[in]	line_buf	Buffer that will be used for reading a line
[in]	len	nr of bytes that fit in line_buf

Definition at line 241 of file shell.h.

shell_run_forever()

static void shell_run_forever ( const shell_command_t * commands, char * line_buf, int len )

inlinestatic

Start a shell and restart it if it exits.

             If `CONFIG_SHELL_SHUTDOWN_ON_EXIT` is set (e.g. on native)
             the shell will instead shut down RIOT once EOF is reached.

Parameters

[in]	commands	ptr to array of command structs
[in]	line_buf	Buffer that will be used for reading a line
[in]	len	nr of bytes that fit in line_buf

Definition at line 222 of file shell.h.

shell_run_once()

void shell_run_once	(	const shell_command_t *	commands,
		char *	line_buf,
		int	len )

Start a shell and exit once EOF is reached.

Parameters

[in]	commands	ptr to array of command structs
[in]	line_buf	Buffer that will be used for reading a line
[in]	len	nr of bytes that fit in line_buf