main函数的三个参数

函数原型：

• int main( int argc, char *argv[], char *envp[] )

   The main function marks the beginning and end of program execution. A C or C++ program must have one function named main. If your code adheres to the Unicode programming model, you can use the wide-character version of main, which is wmain.

函数参数：

• argc

      An integer specifying how many arguments are passed to the program from the command line. Because the program name is considered an argument, argc is at least 1.
  

• argv

       An array of null-terminated strings. It can be declared as an array of pointers to char (char *argv[ ] or wchar_t *argv[ ] for wmain) or as a pointer to pointers to char (char **argv or wchar_t **argv for wmain). The first string (argv[0]) is the program name, and each following string is an argument passed to the program from the command line. The last pointer (argv[argc]) is NULL.
  

• envp

        A pointer to an array of environment strings. It can be declared as an array of pointers to char (char *envp[ ]) or as a pointer to pointers to char (char **envp). If your program uses wmain instead of main, use the wchar_t data type instead of char. The end of the array is indicated by a NULL pointer. The environment block passed to main and wmain is a “frozen” copy of the current environment. If you subsequently change the environment via a call to putenv or _wputenv, the current environment (as returned by getenv/_wgetenv and the _environ/ _wenviron variable) will change, but the block pointed to by envp will not change. This argument is ANSI compatible in C, but not in C++.
  

  ---

三个参数：
argc表示有多少个命令行参数，第一个就是执行程序名，所以argc最少为1。
argv是具体的参数。
envp是系统的环境变量，很少有介绍的。“名称=值”的形式，以NULL结束。

其他：

    *envp: 安符串数组。envp[] 的每一个元素都包含ENVVAR=value形式的字符串。其中ENVVAR为环境变量如PATH或87。value 为ENVVAR的对应值如C:\DOS, C:\TURBOC(对于PATH) 或YES(对于87)。

    Turbo C2.0启动时总是把这三个参数传递给main()函数, 可以在用户程序中说明(或不说明)它们, 如果说明了部分(或全部)参数, 它们就成为main()子程序的局部变量。

Test Code:

int main( int argc, char *argv[], char *envp[] )
{
    for ( int i = 0; i < argc; ++i )
    {
        printf( "%d : %s \n", i, argv[ i ] );
    }

    for( int i = 0; envp[i] != NULL; ++i ) 
    {
        printf( "%d : %s \n", i, envp[ i ] );
    }
    return 0;
}

• < 部分摘自 CSDN>