12 B 文件输入输出

cin.get();
cin.getline();
cin.putback();

cout.put(char);
<< endl ; 对应getline（）;

//技巧：cout.put(cin.get());输出输入的字符

include

include

include

include

using namespace std;

int main()
{
ofstream fout("a.txt");
char a,b,c,d;
a = cin.get();
cin.get(b); //输入一个字符
cin.get(c).get(d);

fout << a << endl;
fout << b << endl;
fout << c << endl;
fout << d << endl;
fout.close();
string s;
ifstream fin("a.txt");
if(!fin)
{
cout << "error" << endl;
}

while(getline(fin,s,'\n'))
{
for(int i = 0; i < 5; i++)
{
long t = time(NULL);
while(time(NULL) == t);
cout << s < }
}
}
//==================================

include

include

include

include

using namespace std;

int main(int argc, char* argv[])
{

ifstream fin(argv[1]);
char ch;
/*for(;;)
{
fin.get(ch); //输入字符到 ch中
if(!fin)
break;
time_t t = time(NULL);
while(time(NULL) == t);
cout << ch << flush; //直接从缓存区中读取
}
fin.close();
*/

while(fin.get(ch)) //两种一样
{
if (!fin)
{
break;
}
time_t t = time(NULL);
while(time(NULL) == t);
cout << ch << flush;
}
fin.get();
}
//============================
//===========================
//==========================
//=========================
cin.getline（字符数组名，长度）//防止长度溢出，确保长度要比实际长度要长
char string1【256】
cin。getline（string1,257）//get whole line
cin >> string 1;//stop at the 1 blank space;

getline(cin,str)//从文件中读取
//===========================

include

include

using namespace std;

include

int main()
{

string str;
char buf[20];
cout << "input a line" << endl;
getline(cin,str);
cout << "str = " << str << endl;
cout << "input a line(<20)" << endl;
cin.getline(buf,20);
cout << "buf = " << buf << endl;

cin.clear(); //但是如果存在cin.clear（）。就可以清空缓存区。。buf没有字节的限制

//当读的元素大于20，输入错误状态。就不再执行任何输入
if (!cin)
{
cout << "read error state" << endl;
}

int n;
cout << "input an integer" << endl;
cin >> n;
cout << "n = " << n < }
：：有cin。clear（）主看buf 存储

没cin.clear()

include

include

using namespace std;

include

int main()
{
ifstream fin("a.txt");
string str;
getline(fin,str,':'); //读字符串，读到： 结束
cout << "username:"<< str<< endl;

getline(fin,str,':');
cout << "password:"<< str<< endl;

getline(fin,str,':');
cout << "user id:"<< str<< endl;

getline(fin,str,':');
cout << "group id:"<< str << endl;

getline(fin,str);
cout << "info:" << str << endl;
cout << "first ch (only one)" << endl;
char no;
char ch = cin.get();
fin.clear();
char name[20];
cout << ch<< endl;//只输出一个字符
cout << "switch ASCLL " << endl;
cout << cin.get()<< flush; //将输入的字符转换为ASCLL
//===================================
cin.clear();
cout <<" second ch "< ch = cin.peek(); //peek 偷看功能（偷看下一个字符施舍么）
cout << ch < if (ch >= '0' &&ch <= '9' )
{
cin >> no;
cout << "no = " << no < }
else
{
cin.getline(name,20);
cout << "name = " << name<< endl;

}
//a.txt 内容：china:123456:477:147:please into
//从文件中依次读取读取

}
//getline(cin,str,'\n'); 到\n结束
//cin.getline(cin,str,'\n');
//peek TK 偷看输入流的字符，返回Ascll
//cin.putback 把取走的字符，退回到输入符中

//putback()

include

include

include

using namespace std;
int main()
{
char ch;
int n;
cout << "input an integer "<< endl;
cin.get(ch);//get会读走一个字符
cin >> n;
cout << "ch = " << ch << endl;
cout << " n = " << n << endl;
cout << "input an integer "<< endl;
cin.get(ch);
cin.putback(ch);//读走一个字符，再读回去
cin >> n;
cout << "ch = " << ch << endl;
cout << " n = " << n << endl;
//putback(ch 现在是换行符，putback是将第一次输入的3869\n，中的换行符输出了出来)
}