用ifstream打开一个不存在文件导致fail.在clear和close之后open一个存在的文件,为何还是fail?

[97jy059]

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
string fn;
cout<<"Enter file name:";
cin>>fn;
ifstream READ(fn.c_str());
if(READ.fail()){
cerr<<"open "<<fn<<" failed.try again\n";
READ.clear();
READ.close();
cout<<"Enter file name:";
cin>>fn;
READ.open(fn.c_str());
if(READ.good()) cout<<"good\n";
else cout<<"unfortunately\n";
}
}

E:\TEMP>test
Enter file name:vc7.txt

E:\TEMP>test
Enter file name:aaaaa
open aaaaa failed.try again
Enter file name:vc7.txt
unfortunately

borland和.net都这样

[cngdzhang]

如果
READ.fail()
那么文件就根本没打开
后面的
READ.clear();
READ.close();

都是没必要的

• 打赏
• 举报

回复 赞

[RookieStar]

There is something wrong with your control logic, recommend like the following:

if (READ.fail())
{
cerr<<"open "<<fn<<" failed.try again\n";
exit(1);
}
else
{
// do your operations here: such as clear()
}

READ.close(); // close your opened file at the end

// This is a common way of file manipulation.

• 打赏
• 举报

回复 赞

[ohokay]

按理说不应该出现你所说的问题，除非你输入的文件名不是和源程序在同一目录下，这样的话你最好输入完整路径就ok了

• 打赏
• 举报

回复 赞

[xiaonian_3654]

打开模式不对！

• 打赏
• 举报

回复 赞

[rorot]

READ.clear();
//READ.close(); 把这里得READ.close()去掉

• 打赏
• 举报

回复 赞

[97jy059]

rorot() :你的方法对的。不过为什么不要执行close呢？

• 打赏
• 举报

回复 赞

[pacman2000]

一个没打开的文件，对它close()，仍然是fail啊。

• 打赏
• 举报

回复 赞