ifstream继承自istream类，istream类只有一个iostream>iostream库中创建好的cin对象，对应一个输入设备就是pc机的键盘，而ifstream类则没有在fstream中有创建好的对象，原因上一篇文章已经说了。

ifstream是文件输入类，输入的源是文件，目标是内存，从文件向内存输入，也就是读取文件的意思了。

#include <<a class="tags" href="/tags/IOSTREAM.html" title=<a class="tags" href="/tags/IOS.html" title=ios>ios</a>tream><a class="tags" href="/tags/IOS.html" title=ios>ios</a>tream</a>> #include <fstream> #include <<a class="tags" href="/tags/STRING.html" title=string>string</a>> using namespace std; int _tmain(int argc, _TCHAR* argv[]) { ifstream hFileRead("c://1.txt", <a class="tags" href="/tags/IOS.html" title=ios>ios</a>::in, _SH_DENYRW); // denies read and write if (!hFileRead) { cout << "read fail!" << endl; exit(1); } char ch; <a class="tags" href="/tags/STRING.html" title=string>string</a> content; while (hFileRead.get(ch)) // the get method retuan false on read end { content += ch; // <a class="tags" href="/tags/STRING.html" title=string>string</a> support oprator+=, use overload cout.put(ch); } <a class="tags" href="/tags/SYSTEM.html" title=system>system</a>("pause"); // other process can't read or write the <a class="tags" href="/tags/FILE.html" title=file>file</a> hFileRead.close(); <a class="tags" href="/tags/SYSTEM.html" title=system>system</a>("pause"); return 0; }

 

使用std::getline这个全局函数来获取一行字符，使用如下：

#include <<a class="tags" href="/tags/IOSTREAM.html" title=<a class="tags" href="/tags/IOS.html" title=ios>ios</a>tream><a class="tags" href="/tags/IOS.html" title=ios>ios</a>tream</a>> #include <fstream> #include <<a class="tags" href="/tags/STRING.html" title=string>string</a>> using namespace std; int _tmain(int argc, _TCHAR* argv[]) { fstream hFile; hFile.open("c://1.txt", <a class="tags" href="/tags/IOS.html" title=ios>ios</a>::out | <a class="tags" href="/tags/IOS.html" title=ios>ios</a>::in, _SH_DENYWR); //only deny write <a class="tags" href="/tags/STRING.html" title=string>string</a> str; while(std::getline(hFile, str)) cout << str << endl; hFile.close(); cin.get(); return 0; }

 

zz from: http://www.cnblogs.com/coderlee/archive/2008/01/22/1047990.html