C++文件读写详解（ofstream,ifstream,fstream）

记录学习心得，资料转自：晨雪无痕 原创：C++文件读写详解（ofstream,ifstream,fstream）

 一、在Ubuntu平台编译运行验证

1. 编译运行命令

clear \r
rm  ./out/* \r
g++  -o ./out/hello hello.c && ./out/hello \r

2.头文件

hello.h

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>

#include <sys/stat.h>
#include <iostream>
#include <fstream>
using namespace std;

二、函数验证

test_fstream

int test_fstream()
{<span style="font-family: Arial, Helvetica, sans-serif;">//From: http://blog.csdn.net/kingstar158/article/details/6859379/</span>

 char line1[]="This is a line.\n";
char line2[]="This is another line.\n";
const char *f = "file_out.txt";
const char *filename = "file_out.bin";
#if 0
char line1[]="This is a line.\n";
char line2[]="This is another line.\n";
ofstream out("file_out.txt");
if(out.is_open())
{
printf("line1.lenth = %d\n",strlen(line1));
printf("line2.lenth = %d\n",strlen(line2));
out << line1;	// 16
out << line2;	// 16
out.close();
}
#elif 0	// text file
char buffer[256];

struct stat st;
stat(f,&st);
printf("st_mode = %x\n", st.st_mode);
char m=6;
//	int v= chmod(f, m<<6|m<<3|m); 		//  -rwxrwxrwx		-rwxXSt
int v= chmod(f, 0777);
printf("st_mode = %x\n", st.st_mode);

ifstream in(f);

if(! in.is_open())
{
cout << "Error: opening file fail!\n\n";
cout << "in.bad()  "<< in.bad() << endl;
cout << "in.fail() "<< in.fail() << endl;
cout << "in.eof()  "<< in.eof() << endl;
cout << "in.good() "<< in.good() << endl;
exit(1);
}
while(!in.eof())
{
in.getline (buffer,100);
cout << buffer << endl;
}
#elif 0// 1 // binary file
long l,m;
ifstream in(filename, ios::in|ios::binary);
if (!in.is_open())
{
printf("Error: ");
cout << "in.bad()  "<< in.bad() << endl;
cout << "in.fail() "<< in.fail() << endl;
cout << "in.eof()  "<< in.eof() << endl;
cout << "in.good() "<< in.good() << endl;
//	exit(1);
}
l = in.tellg();
in.seekg(0, ios::end);
m = in.tellg();
in.close();

cout << "size of " << filename;
cout << " is: " << (m-1) << " Bytes.\n";
#elif 0 // 2 // binary file read
char * buffer;
long size;
//	fstream in(filename, ios::in|ios::binary|ios::ate);
fstream in(filename, ios::binary|ios::ate|/*ios::out|*/ios::in);
if (!in.is_open())
{
printf("Error: ");
cout << "in.bad()  "<< in.bad() << endl;
cout << "in.fail() "<< in.fail() << endl;
cout << "in.eof()  "<< in.eof() << endl;
cout << "in.good() "<< in.good() << endl;
//	exit(1);
}
size = in.tellg();
cout << "size = " << size << endl;
in.seekg(0,ios::beg);

buffer = new char [size];
in.read(buffer,size);

cout << "the complete file is in a buffer\n";
printf("buffer[%ld] = \n%s\n", size, buffer);
in.close();
delete[] buffer;
#elif 3 // binary file write
const char *filenameOut = "file_out2.bin";
ofstream out(filenameOut, ios::binary|ios::ate|ios::out);
if (!out.is_open())
{
printf("Error: ");
cout << "in.bad()  "<< out.bad() << endl;
cout << "in.fail() "<< out.fail() << endl;
cout << "in.eof()  "<< out.eof() << endl;
cout << "in.good() "<< out.good() << endl;
//	exit(1);
}
#define MAX 	 6
unsigned char data[]={ 0xb8,0x3d,0x4e,0x01,0x02,0x03,0};
//printf("buffer[%d] = \n%s\n", MAX, data);
printf("buffer[%d] = { ",MAX);
unsigned char i=0;
while(data[i])
{
printf("0x%x, ", data[i++]);
}
printf(" };\n");

out.seekp(0,ios::beg);

out.write((char *)&data[0],MAX);
out.tellp();
out.close();

#elif 4 // 测试 <span style="font-family: Arial, Helvetica, sans-serif;">ftell()获取文件大小</span>

<span style="white-space:pre">			</span>long fsize;
<span style="white-space:pre">			</span>#define FILE_NAME<span style="white-space:pre">	</span>"file_out3.bin"
<span style="white-space:pre">			</span>FILE *stream;
<span style="white-space:pre">			</span>stream= fopen(FILE_NAME, "r");
<span style="white-space:pre">			</span>if(NULL != stream)
<span style="white-space:pre">			</span>{
<span style="white-space:pre">				</span>fsize = ftell(stream);
<span style="white-space:pre">				</span>printf("fsize = %ld\n",fsize);
<span style="white-space:pre">				</span>fseek(stream, 0 ,SEEK_END);
<span style="white-space:pre">				</span>fsize = ftell(stream);
<span style="white-space:pre">				</span>printf("fsize = %ld\n",fsize);
<span style="white-space:pre">			</span>fclose(stream);

<span style="white-space:pre">			</span>}
#else
#error: "Not set"
#endif
return 0;
}