读写方式打开文件，竟然不能写？？？？为啥_file = open 无法写入文字-优快云博客

本文通过一个具体的示例展示了如何使用C++中的文件流（fstream）进行文件的读写操作，并实现两个有序文件的合并。代码中包含了文件打开、读取、写入等关键步骤，对于理解C++文件流的使用方式很有帮助。

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#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std ;
void main()
{
int data1 , data2 ;
fstream infile1 , infile2 , outfile ;
infile1.open ( "f.dat" , ios::in | ios::out | ios::binary ) ; //因为没有预先的文件，所以自己建立升序
if ( ! infile1 )
{
  for ( int i = 0 ; i <= 10 ; i +=2 )
  {
   data1 = i ;
   infile1 << "dfsfadfa" << data1 ;     //实际上竟然没写进去？？？不懂

}
infile1.seekg ( 0 , ios::end ) ; //找出末指针
long end1 = infile1.tellp() ; //记录末指针
infile2.open ( "g.dat" ,ios::in | ios::out | ios::binary ) ;
if ( ! infile2 )
{
  for ( int j = 1 ; j <= 10 ; j +=2 )
  {
   data2 = j ;
   infile2.write ( ( char * ) & data2 , sizeof( int ) ) ;
  }
}
infile2.seekg ( 0 , ios::end ) ;
long end2 = infile2.tellp() ;
outfile.open ( "h.dat" , ios::in | ios::out | ios::binary ) ;
infile1.seekg ( 0 , ios::beg ) ;
infile2.seekg ( 0 , ios::beg ) ;
while ( ( long )infile1.tellp() != end1 && ( long )infile2.tellp() != end2 ) //排序
{
  infile1.read ( ( char * )&data1 , sizeof( int ) ) ;
  infile2.read ( ( char * )&data2 , sizeof( int ) ) ;
  if( data1 < data2 )
        {
   outfile.write ( ( char * )&data1 , sizeof( int ) ) ;
   infile2.seekg ( -( long )sizeof( int ) , ios::cur ) ;
        }
  else
        {
   outfile.write ( ( char * )&data2 , sizeof( int ) ) ;
   infile1.seekg ( -( long )sizeof(int) , ios::cur ) ;
        }
}
while ( ( long )infile1.tellp() != end1 )
{
    infile1.read ( ( char * )&data1 , sizeof( int ) ) ;
       outfile.write ( ( char * )&data1 , sizeof( int ) ) ;
}
    while ( ( long )infile2.tellp() != end2 )
    {
  infile2.read ( ( char * )&data2 , sizeof( int ) ) ;
        outfile.write ( ( char * )&data2 , sizeof( int ) ) ;
    }
cout << "文件合并完！" << endl ;
infile1.close() ;
infile2.close() ;
outfile.close() ;
//system ( "pause" ) ;
}