第16周 阅读程序 4



*Copyright(c) 2016.烟台大学计算机与控制工程学院
*ALL rights  reserved.
*文件名称：main.cpp
*作者：孙亚茹
*完成日期：2016年6月20日
*问题描述：阅读下面程序，体会seekg(),tellg()等函数的用法。
*/

#include<iostream>#include <fstream>using namespace std;const char * filename = "a.txt";int main (){    long l,m;    ifstream file (filename, ios::in|ios::binary);    l = file.tellg();    file.seekg (0, ios::end);    m = file.tellg();    file.close();    cout << "size of " << filename;    cout << " is " << (m-l) << " bytes.\n";    return 0;}

总结：

          读文件a中的数据，统计字符个数。

（2）

#include <fstream>using namespace std;int main (){    long pos;    ofstream outfile;    outfile.open ("test.txt");    outfile.write ("This is an apple",16);    pos=outfile.tellp();    outfile.seekp (pos-7);    outfile.write (" sam",4);    outfile.close();    return 0;}

总结：

          向文件中写入数据。

（3)

</pre><pre class="cpp" name="code">#include <iostream>#include <fstream>using namespace std;int main(){    fstream outfile,infile;    outfile.open("data.txt",ios::out);    for (int i=0; i<26; i++)        outfile<<(char)('A'+i);    outfile.close();    infile.open("data.txt",ios::in);    char ch;    infile.seekg(6,ios::beg);    if(infile.get(ch))        cout<<ch;    infile.seekg(8,ios::beg);    if(infile.get(ch))        cout<<ch;    infile.seekg(-8,ios::end);    if(infile.get(ch))        cout<<ch;    cout<<endl;    infile.close();    return 0;}