/****************************************************************************
* returns:
* 1 - command executed, repeatable
* 0 - command executed
but not repeatable, interrupted commands are
* always considered not
repeatable
* -1 - not executed (unrecognized, bootd recursion or too many
args)
* (If cmd is NULL or "" or longer than CFG_CBSIZE-1 it
is
* considered unrecognized)
*
* WARNING:
*
* We
must create a temporary copy of the command since the command we get
* may
be the result from getenv(), which returns a pointer directly to
* the
environment data, which may change magicly when the command we run
* creates
or modifies environment variables (like "bootp" does).
*/
int run_command (const char *cmd, int flag)
{
cmd_tbl_t
*cmdtp;
char cmdbuf[CFG_CBSIZE]; /* working copy of cmd */
char
*token; /* start of token in cmdbuf */
char *sep; /* end of token
(separator) in cmdbuf */
char finaltoken[CFG_CBSIZE];
char *str =
cmdbuf;
char *argv[CFG_MAXARGS + 1]; /* NULL terminated */
int argc,
inquotes;
int repeatable = 1;
int rc = 0;
#ifdef DEBUG_PARSER
printf ("[RUN_COMMAND] cmd[%p]=\"", cmd);
puts
(cmd ? cmd : "NULL"); /* use puts - string may be loooong */
puts
("\"\n");
#endif
clear_ctrlc(); /* forget any previous Control C */
if (!cmd || !*cmd) { //先是对命令的有效性进行检测
return -1; /* empty command
*/
}
if (strlen(cmd) >= CFG_CBSIZE) {//判断命令的长度是否在允许的范围内
puts ("## Command
too long!\n");
return -1;
}
strcpy (cmdbuf, cmd);//备份命令
/* Process separators and check for invalid
* repeatable commands
*/
#ifdef DEBUG_PARSER
printf ("[PROCESS_SEPARATORS] %s\n",
cmd);
#endif
while (*str) { // 输入的字符串是否为空
/*
* Find separator, or string end
* Allow simple escape of ‘;‘
by writing "\;"
*/
//下边的for循环是寻找输入命令的分割符或者结尾，因为uboot允许一次输入多个命令
//每次处理一个命令
for (inquotes = 0,
sep = str; *sep; sep++) {
if ((*sep==‘\‘‘) &&
(*(sep-1)
!= ‘\\‘))
inquotes=!inquotes;
if (!inquotes &&
(*sep == ‘;‘) && /*
separator */
( sep != str) && /* past string start */
(*(sep-1) != ‘\\‘)) /* and NOT escaped */
break;
}
/*
* Limit the token to data between separators
*/
token =
str;//token指向命令的开头
if (*sep) {
//如果是分隔符的话，将分隔符替换成空字符
str = sep +
1; /* start of command for next pass */
//str指向下一句的开头
*sep =
‘\0‘;
}
else
str = sep; /* no more commands for next pass
*/
//如果没有其他命令了，就指向命令的尾部
#ifdef DEBUG_PARSER
printf ("token:
\"%s\"\n", token);
#endif
/* find macros in this token and replace them */
process_macros
(token, finaltoken);
//将命令中的宏替换掉，例如$(kernelsize)替换成内核的大小
/*
Extract arguments */
//提取参数，将每一个参数用‘\0‘分开，argv中的每一个指针指向一个参数
//的起始地址，返回值为参数的个数
if ((argc =
parse_line (finaltoken, argv)) == 0) {
rc = -1; /* no command at all
*/
continue;
}
/* Look up command in command table */
if ((cmdtp = find_cmd(argv[0]))
== NULL) {
//第一个参数就是要运行的命令，首先在命令表中找到它的命令结构体指针
printf ("Unknown command
‘%s‘ - try ‘help‘\n", argv[0]);
rc = -1; /* give up after bad command
*/
continue;
}
/* found - check max args */
if (argc > cmdtp->maxargs)
{//检查输入命令的参数是否在允许范围内
printf ("Usage:\n%s\n", cmdtp->usage);
rc =
-1;
continue;
}
#if (CONFIG_COMMANDS & CFG_CMD_BOOTD)
/* avoid "bootd" recursion
*/
if (cmdtp->cmd == do_bootd) {
#ifdef DEBUG_PARSER
printf
("[%s]\n", finaltoken);
#endif
if (flag & CMD_FLAG_BOOTD)
{
puts ("‘bootd‘ recursion detected\n");
rc =
-1;
continue;
} else {
flag |=
CMD_FLAG_BOOTD;
//
}
}
#endif /* CFG_CMD_BOOTD */
/* OK - call function to do the command */
if ((cmdtp->cmd) (cmdtp,
flag, argc, argv) != 0) {//执行命令
rc = -1;
}
repeatable &= cmdtp->repeatable;//设置命令重复执行标志，也就是按enter直接执行上次命令
/* Did the user stop this? */
//检查是否有control+c按下，如果有就结束当前命令
if
(had_ctrlc ())
return 0; /* if stopped then not repeatable */
}
return rc ? rc : repeatable;
}
原文：http://www.cnblogs.com/amanlikethis/p/3556128.html