c++ 读写文件出错

[feel8]

判断一个文件存在不存在？
如果不存在，写进一个数字1
如果存在，读出数字，加一后再存入，直到读出的数字为100，执行test()函数。

下面的代码可以写1进去，但是读出后就变成一串数字？

#include "iostream.h"
#include "fstream.h"
using namespace std;

#define NUM_FILE "D:\\test.txt"

int main()
{
int i;

ifstream r_file(NUM_FILE, ios::binary);

if(!r_file)
{
r_file.close();
ofstream w_file(NUM_FILE, ios::binary);
w_file << 1;
w_file.close();
}
else
{
cout << r_file.get();
i << r_file.get();
cout << i;
}


system("pause");
return(0);


}

[taodm]

i << r_file.get();
你想干什么？这是对i作左移操作。

[healer_kx]

我只会CreateFile和FILE*,不会流...

[feel8]

因为我直接输出cout << r_file.get();的时候就是一串数字，
所以想放到一个整数变量里再输出。

应该怎么弄？

[feel8]

判断一个文件存在不存在？
如果不存在，写进一个数字1
如果存在，读出数字，加一后再存入，直到读出的数字为100，执行test()函数。

下面的代码可以写1进去，但是读出后就变成一串数字？

#include "iostream.h"
#include "fstream.h"
using namespace std;


#define NUM_FILE "D:\\test.txt"

int main()
{
int i;

ifstream r_file(NUM_FILE, ios::binary);

if(!r_file)
{
r_file.close();
ofstream w_file(NUM_FILE, ios::binary);
w_file << 1;
w_file.close();
}
else
{
cout << r_file.get();
r_file.close();
}


system("pause");
return(0);


}

就是这样，原来就是这样的，输出了一串数字“494198592”

[kouzhongling]

#include "iostream"
#include "fstream"
#include <vector>
using namespace std;

#define NUM_FILE "D:\\test.txt"

int main()
{
int i;
int n;

char ch;
vector<char> vc;
vector<char>::iterator it;

ifstream r_file(NUM_FILE, ios::binary);

if(!r_file)
{
r_file.close();
ofstream w_file(NUM_FILE, ios::binary);
w_file << 1;
w_file.close();
}
else
{


while((r_file.get(ch)!='\0')&&!r_file.eof())
vc.push_back(ch);

for(it=vc.begin();it!=vc.end();it++)
cout<<*it;
cout<<endl;
}


system("pause");
return(0);


}

[lann64]

r_file>>i;//读入

[lann64]

#include <iostream>
#include <fstream>
using namespace std;

#define NUM_FILE "D:\\test.txt"

int main()
{
int i;

ifstream r_file(NUM_FILE, ios::binary);

if(!r_file)
{
r_file.close();
ofstream w_file(NUM_FILE, ios::binary);
w_file << 1;
w_file.close();
}
else
{
r_file>>i;
cout<<i<<endl;
if (i<100)
{
i++;
r_file.close();
ofstream w_file(NUM_FILE,ios::binary);
w_file<<i;
w_file.close();
}
else
r_file.close();

}


//system("pause");
return(0);


}

[kouzhongling]

给个比较全的
#include "iostream"
#include "fstream"
#include <vector>
using namespace std;

#define NUM_FILE "D:\\test.txt"

int main()
{
int i;
int n;

char ch;
char buf[50]={0};

vector<char> vc;
vector<char>::iterator it;

ifstream r_file(NUM_FILE, ios::binary);

if(!r_file)
{
r_file.close();
ofstream w_file(NUM_FILE, ios::binary);
w_file << 1;
w_file.close();
}
else
{


while((r_file.get(ch)!='\0')&&!r_file.eof())
vc.push_back(ch);

for(it=vc.begin();it!=vc.end();it++)
cout<<*it;
cout<<endl;

it=vc.begin();

sprintf(buf,"%s",it);
n=atoi(buf);

if (!(n<100))
{
return 1;
}
n++;
ofstream w_file(NUM_FILE, ios::binary);
w_file << n;
w_file.close();

cout<<n;

}


system("pause");
return(0);

}

[sw1024]

给个最简单的！
#include <iostream.h>
#include <fstream.h>
#include <stdlib.h>

#define NUM_FILE "D:\\test.txt"

int main()
{
int i=0;
ifstream infile;
infile.open(NUM_FILE,ios::out|ios::nocreate);

if(!infile)
{
ofstream outfile;
outfile.open(NUM_FILE,ios::in);
outfile<<1;
outfile.close();
}
else
{
infile>>i;
infile.close();
i++;
if(i<=100)
{
ofstream outfile;
outfile.open(NUM_FILE,ios::in);
outfile<<i;
outfile.close();
}
else cout<<"OK!"<<endl;
}


system("pause");
return(0);

}

[feel8]

谢谢大家，我再研究一下。。

kouzhongling(还没恋爱) 给的代码好像没法自加一。

lann64(昆仑大鹏＠迦楼罗)的通过了。谢谢。调试的时候连警告都没有。强人。谢谢。。