#include <fstream>
#include <iomanip>
#include <iostream>
////使用文件操作时，不要指望作用域会自动将文件关闭，显示的调用close()函数
int main(int argc, char* argv[])
{
////向文件中写入10个数字
{
std::ofstream fout("out.txt");
if(!fout)
std::cout << "failed to open out.txt" << std::endl;
for(int i = 0; i < 10; ++i)
{
fout << std::setw(3) << i << std::endl;
}
fout.close();
}
////直接显示文件中的所有内容
{
std::ifstream fout("out.txt");
std::cout << fout.rdbuf() << std::endl;
fout.close();
}
////两个文件的复制,使用rdbuf得到文件的内容
{
std::ifstream fin("out.txt");
std::ofstream fout("fcopy.txt");
if(fin && fout == NULL)
{
std::cout <<"open file out.txt error" << std::endl;
return -1;
}
fout << fin.rdbuf();
fin.close();
fout.close();
}
////从文件中读取10个字符
{
std::ifstream fin("out.txt");
if(!fin)
std::cout << "failed to open out.txt" << std::endl;
for(int i = 0; i < 10; ++i)
{
char c;
fin >> std::setw(3) >> c;
////std::cout << c << std::endl;
}
fin.close();
}
////将文件的内容添加行号
{
////一行中最大字符数为256
#define MAX_COLS 256
////行号以8位数字表示
#define LINE_NUM 9
char szLine[MAX_COLS] = {0};
std::ifstream fin("out.txt");
std::ofstream fout("lineno.txt");
if(fin && fout == NULL)
{
std::cout << "open file out.txt or lineno.txt error" << std::endl;
return -1;
}
int i = 0;
char szLineNo[LINE_NUM] = {0};
while (fin.getline(szLine,MAX_COLS))
{
sprintf(szLineNo,"%08d",i++);
fout.write(szLineNo,LINE_NUM); //写入行号
fout.write("\t",1); //行号与文件内容以TAB分隔
fout.write(szLine,strlen(szLine)); //写入文件中的一行内容
fout << std::endl; //写入回车换行符
}
fin.close();
fout.close();
}
////向文件中写入二进制数据
{
std::ofstream fout("out.bin",std::ios::out | std::ios::binary);
if(!fout)
{
std::cout << "open out.bin error" << std::endl;
}
for(int i = 0; i < 10;++i)
{
fout << i;
}
std::ofstream fbin("fbin.bin",std::ios::out | std::ios::binary);
if(!fbin)
{
std::cout << "open fbin.bin error" << std::endl;
return -1;
}
for (int j = 0; j < 10;j++)
{
fbin.write((char*)&j,sizeof(int));
}
fout.close();
}
{
////创建文件数据结构，并将数据写入文件
////结构以4字节对齐,sizeof(CFileData) = 16
struct CFileData
{
int nNo;
char szName[10];
};
std::ofstream fFileData("fFiledata",std::ios::binary | std::ios::out);
if(!fFileData)
{
std::cout << "open file fFileData error" << std::endl;
return -1;
}
for (int i = 0; i <10;++i )
{
CFileData fd;
memset(&fd,0,sizeof(fd));
fd.nNo = i;
sprintf(fd.szName,"%d",i);
fFileData.write((const char*)&fd,sizeof(fd));
}
////将这个文件关闭否则后面的读取操作都会失败
fFileData.close();
////从文件中第五个CFileData开始读取结构数据
std::ifstream fInFile("fFileData",std::ios::binary | std::ios::in);
if(!fInFile)
{
std::cout <<"open file fFileData error" << std::endl;
return -1;
}
std::ios::pos_type pos = fInFile.tellg();
std::cout << pos << std::endl;
////跳过前面的5个结构
fInFile.seekg(5*sizeof(CFileData),std::ios::beg);
for (int i = 0; i < 5;++i)
{
CFileData fd;
memset(&fd,0,sizeof(fd));
fInFile.read((char*)&fd,sizeof(fd));
std::cout << "No. = " << fd.nNo << "\t" << "Name = " << fd.szName << std::endl;
}
fInFile.close();
}
return 0;
}
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