getline用法

发布时间：2018-07-01 09:45:25 来源：文档文库

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GetLine

getline功能

getline参数

getline说明

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getline功能

　　getline是string类对象的成员函数,属于string IO 操作。用于读取整行文本

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getline参数

　　getline(cin,str);

　　cin:输入流

　　str:string对象

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getline说明

　　getline函数从输入流的下一行读取，并保存读取的内容到str中，但不包括换行符。getline 函数将 istream 参数作为返回值，和输入操作符一样也把它用作判断条件。　

　　范例：

　　#include

　　using namespace std;

　　int main()

　　{

　　string line;

　　while(getline(cin,line))

　　cout<

　　return 0;

　　}

　　结果：

　　输入 line1 ----回车换行

　　显示为空

　　输入 line2 ----回车换行

　　显示 line1

　　输入 line3 ----回车换行

　　显示 line2

　　----（以此类推）

getline的原型如下：

getline(char* c,int i,char c); 表示读入i个字符，或者遇到结束符c为止的字符数，保存到c中。

getline(char*,int); 表示读入i个字符到c中。注意读入的字符数应比实际的大1，因为读入的是字符串，字符串将会以'\0'作为结束，如果你要读入3个字符，那么i的值应该为4。

注意getline会读取并丢弃分界符。

后面的自已搞定，创建一个文件流类对象，然后用这个文件流来调用getline函数，比如

ifstream hy1(“hyong1.txt”)//创建hy1流，并打开文件以便读取内容。

char c[333];

hy1.getline(c,3,'0'); //表示，把hy1流关联的hyong1中3个字符或者遇到'0'的字符数读入到c中。

假设有一个叫 data.txt 的文件, 它包含以下内容:

Fry: One Jillion dollars.
[Everyone gasps.]
word/media/image1.gifAuctioneer: Sir, that's not a number.
word/media/image1.gif数据读取，测试。word/media/image1.gif

以下就是基于 data.txt 的数据读取操作:

#include
include
#include
word/media/image1.gif
word/media/image1.gifusing namespace std;
word/media/image1.gif
//输出空行
void OutPutAnEmptyLine()
word/media/image2.gif{
word/media/image4.gif     cout<<"\n";
word/media/image5.gif}
word/media/image1.gif
//读取方式: 逐词读取, 词之间用空格区分
word/media/image1.gif//read data from the file, Word By Word
word/media/image1.gif//when used in this manner, we'll get space-delimited bits of text from the file
word/media/image1.gif//but all of the whitespace that separated words (including newlines) was lost.
word/media/image1.gifvoid ReadDataFromFileWBW()
word/media/image6.gifword/media/image2.gif{
word/media/image4.gif     ifstream fin("data.txt");
word/media/image4.gif    string s;
word/media/image4.gif    while( fin >> s )
word/media/image8.gifword/media/image9.gif    {
word/media/image4.gif         cout << "Read from file: " << s << endl;
word/media/image10.gif     }
word/media/image5.gif}
word/media/image1.gif
word/media/image1.gif//读取方式: 逐行读取, 将行读入字符数组, 行之间用回车换行区分
word/media/image1.gif//If we were interested in preserving whitespace,
word/media/image1.gif//we could read the file in Line-By-Line using the I/O getline() function.
word/media/image1.gifvoid ReadDataFromFileLBLIntoChar()
word/media/image6.gifword/media/image2.gif{
word/media/image4.gif     ifstream fin("data.txt");
word/media/image4.gif    const int LINE_LENGTH = 100;
word/media/image4.gif    char str[LINE_LENGTH];
word/media/image4.gif    while( fin.getline(str,LINE_LENGTH) )
word/media/image8.gifword/media/image9.gif    {
word/media/image4.gif         cout << "Read from file: " << str << endl;
word/media/image10.gif     }
word/media/image5.gif}
word/media/image1.gif
word/media/image1.gif//读取方式: 逐行读取, 将行读入字符串, 行之间用回车换行区分
word/media/image1.gif//If you want to avoid reading into character arrays,
word/media/image1.gif//you can use the C++ string getline() function to read lines into strings
word/media/image1.gifvoid ReadDataFromFileLBLIntoString()
word/media/image6.gifword/media/image2.gif{
word/media/image4.gif     ifstream fin("data.txt");
word/media/image4.gif    string s;
word/media/image4.gif    while( getline(fin,s) )
word/media/image8.gifword/media/image9.gif    {
word/media/image4.gif         cout << "Read from file: " << s << endl;
word/media/image10.gif     }
word/media/image5.gif}
word/media/image1.gif
word/media/image1.gif//带错误检测的读取方式
word/media/image1.gif//Simply evaluating an I/O object in a boolean context will return false
word/media/image1.gif//if any errors have occurred
word/media/image1.gifvoid ReadDataWithErrChecking()
word/media/image6.gifword/media/image2.gif{
word/media/image4.gif    string filename = "dataFUNNY.txt";
word/media/image4.gif     ifstream fin( filename.c_str());
word/media/image4.gif    if( !fin )
word/media/image8.gifword/media/image9.gif    {
word/media/image4.gif         cout << "Error opening " << filename << " for input" << endl;
word/media/image4.gif         exit(-1);
word/media/image10.gif     }
word/media/image5.gif}
word/media/image1.gif
word/media/image1.gifint main()
word/media/image6.gifword/media/image2.gif{
word/media/image4.gif     ReadDataFromFileWBW(); //逐词读入字符串
word/media/image4.gif     OutPutAnEmptyLine(); //输出空行
word/media/image4.gif
word/media/image4.gif     ReadDataFromFileLBLIntoChar(); //逐词读入字符数组
word/media/image4.gif     OutPutAnEmptyLine(); //输出空行
word/media/image4.gif
word/media/image4.gif     ReadDataFromFileLBLIntoString(); //逐词读入字符串
word/media/image4.gif     OutPutAnEmptyLine(); //输出空行
word/media/image4.gif
word/media/image4.gif     ReadDataWithErrChecking(); //带检测的读取
word/media/image4.gif    return 0;
word/media/image5.gif}

输出结果为:
Read from file: Fry:
Read from file: One
Read from file: Jillion
Read from file: dollars.
Read from file: [Everyone
Read from file: gasps.]
Read from file: Auctioneer:
Read from file: Sir,
Read from file: that's
Read from file: not
Read from file: a
Read from file: number.
Read from file: 数据读取，
Read from file: 测试
Read from file: 。

Read from file: Fry: One Jillion dollars.
Read from file: [Everyone gasps.]
Read from file: Auctioneer: Sir, that's not a number.
Read from file: 数据读取，测试。

Read from file: Fry: One Jillion dollars.
Read from file: [Everyone gasps.]
Read from file: Auctioneer: Sir, that's not a number.
Read from file: 数据读取，测试。

Error opening dataFUNNY.txt for input
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