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一个简易的Linux下的shell源代码

TINYSH: MINIMAL SHELL
=====================

The purpose of the tinysh library is to provide a fully fonctional
shell support to a system as soon as we are able to read/write
characters to/from a device. This suits particularly well to embedded
systems when developers just made the uart work.

As embedded systems often do not have full libc support, the library
is written without any use of external functions nor include of any
system header.

The package contains a main.c file that can be used as an example
to demonstrate tinysh usage.


INSTALLATION
------------
Run the commands:
./configure
make all

You just built the ./tinysh program. Run it and type "help" for
further instructions.


USING TINYSH
------------

The application must pass every single input character to function
tinysh_char_in. In addition, the application must provide a 
tinysh_char_out function to write characters to output device

For example:

    void tinysh_char_out(unsigned char c)
    {
       put_char_to_uart(c);
    }
    ...
    while(1)
    {
       unsigned char c;
       c=get_char_from_uart(); /* we assume this fnt is blocking */
       tinysh_char_in(c);
    }
    ... 

The application must provide each command by instantiating a
tinysh_cmd_t structure:

typedef struct tinysh_cmd_t {
  struct tinysh_cmd_t *parent; /* 0 if top level command */
  char *name;                  /* command input name, not 0 */
  char *help;                  /* help string, can be 0 */
  char *usage;                 /* usage string, can be 0 */
  tinysh_fnt_t function;       /* function to launch on cmd, can be 0 */
  void *arg;                   /* current argument when function called */
  struct tinysh_cmd_t *next;   /* must be set to 0 at init */
  struct tinysh_cmd_t *child;  /* must be set to 0 at init */
} tinysh_cmd_t;

and passing the pointer to this structure to function tinysh_add_command.

For example:

void hello_fnt(int argc, char **argv)
{
    printf("hello world\n");
}

tinysh_cmd_t hello_cmd={0,"hello","display hello","<cr>",
    hello_fnt,0,0,0};

...
tinysh_add_command(&hello_cmd);
...

Read file main.c for more advanced usage.


TINYSH SUPPORTS
---------------

-command registration: application adds commands dynamically 

-sub-commands: allows any number of command level. For instance: 
    "$ memory read bytes <address> <size>" is supported and the 
    developer does not have to make a single "memory-read-bytes"
    command.

-contexts: the system remembers about contexts between inputs, 
    for instance, from the previous example, typing "memory<cr>"
    leads to prompt "$ memory >" so the next input can be simply
    "read bytes <xx> <yy>". Use "/" to return to top level.

-previous commands retrieval: by using CTRL-P and CTRL-N

-partial command word: there is no need to type the whole
    command word if there is no ambiguity on what has already been 
    typed.

-auto-completion: using <TAB>

-help and usage display: using "?", display help related to current 
    input line.

-string to decimal/hexadecimal conversion: this is not really a shell
    feature but this is often very useful in the environment where
    tinysh can be used. Strings starting with 0x are converted to 
    hexadecimal.

-echo control: it is possible for the application to enable/disable
    character echo.

-dynamic argument: to allow several commands to share the same function 
    callback, the callback can retrieve an additional argument for the 
    current  command.

-prompt change: application can change shell prompt.

TINYSH DOES NOT SUPPORT
-----------------------

-line edition: only backspace is supported

-multiple shells within the same data space: this could be done
    by adding a new parameter to all functions. This parameter would
    be a pointer to a structure containing all currently global 
    variables. As tinysh is not allowed to use dynamic memory
    allocation (which may not be available in the system), an
    empty structure (all 0s) must be provided by the application at
    shell instance init. As we want to keep simple things simple,
    the tinysh library should support one instance and current 
    functions must remain unchanged by using macros. This is to
    be done.

-application driven context: it is not possible to have contexts
    such as "$ subsystem <subsys-name> > " if <subsys-name> is not
    determined at compile time. It will added when there will be a 
    real need for it.


BUGS
----

Please report bugs to "Michel Gutierrez"<[e-mail]>