获取文件访问类型

#include <sys/types.h>
#include <fcntl.h>
#include <iostream>
using namespace std;

int main(int argc, char* argv[])
{
	int	nMode = 0;
	int	nVal = 0;

	if (2 != argc)
	{
		cout <<"usage: file_info.exe <descriptor>";
		return -1;
	}

	if ((nVal = fcntl(atoi(argv[1]), F_GETFL, 0)) < 0)
	{
		cout << "fcntl error for fd %d" << atoi(argv[1]) << endl;
		return -1;
	}

	nMode = nVal & O_ACCMODE;
	switch (nMode)
	{
	case O_RDONLY:
		cout << "read only" << endl;
		break;
		
	case O_WRONLY:
		cout << "write only" << endl;
		break;

	case O_RDWR:
		cout << "read & write" << endl;
		break;

	default:
		cout << "unknown access mode" << endl;
		break;
	}

	if (nVal & O_APPEND)
	{
		cout << "append" << endl;
	}

	if (nVal & O_NONBLOCK)
	{
		cout << "nonblocking" << endl;
	}

	if (nVal & O_SYNC)
	{
		cout << "synchronous writes" << endl;
	}
		
	return 0;
}