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    Forgive my ugly English description ,and i may it will help you. -_-
    (Reference by : http://www.cplusplus.com/reference/iostream/istream/getline.html)
    the function prototype is as follows:
    istream& getline (char* s, streamsize n );
    istream& getline (char* s, streamsize n, char delim );
    
    the function extracts charatcters from the input sequence and stores them as c-tring into the array begin at s. Characters are extracted until either n-1 characters have been extracted or the delimiting character is found.( the char delim can be specified by yourself, or be '\n' by default). Remember this, when the delimiter is found ,it will be extracted and discarded, i.e, it is extracted from the input stream and not stored to the s , and the next input operation will begin after this extracted delimiter. ). After the data extracted ,the ending null charactor ('\0') will be appended to s automatically.
    The following is same examples.
    
 1 #include<iostream>
 2 using namespace std;
 3 int main()
 4 {
 5     char fruit[100];
 6     cin.getline(fruit,100,'*');
 7     cout<<fruit<<endl;
 8     
 9     system("pause");
10 }
11 
    
    now ,when you input "banana apple pear\n"( here \n means the enter), then the console will show "banana apple pear"
   
   also ,you can specify the delimiter by yourself  as this.
  
 1 #include<iostream>
 2 using namespace std;
 3 int main()
 4 {
 5     char fruit[100];
 6     cin.getline(fruit,100,'*');
 7     cout<<fruit<<endl;
 8     
 9     system("pause");
10 }
11 
    now,when you input "banana apple pear * orange\n",then the console will show " banana apple pera" , here the orange is not readed because is is after the delimiter '*'.
    
    So simple about use this function ,right ? now see this example .
    
 1 #include<iostream>
 2 using namespace std;
 3 int main()
 4 {
 5     char fruit[100];
 6     while(cin.getline(fruit,100,'*'))
 7     {
 8         cout<<fruit<<endl;
 9     }
10     
11     system("pause");
12 }
13 
  Here we want to input number of lines ,each of line is delimited by a '*'.
  In the first time : we input " banana apple *\n" then the console show "banana apple" ,this is right.
  But the problem comes, in the second input " pear orange *\n", now the console show "\n(\n means a blank line) pear orange". Here a blank line will be output, betray to our will that showing "pear orange";
   The problem is that a '\n' is stored in the fruit in the second time as the first element, i.e, the fruit is "\npear orange\0" in the second input. In the first getline ,it extracted the input stream until the first '*' was found, then it discarded the '*', but the following character is '\n' which you input in the first time, this '\n' is still in the input stream. And the second getline read the stream form this '\n'. As we know ,the delimiter is specified as '*' ,so the '\n' is not a delimiter here ,and it will be stored into the second fruit. 
   How to resovle this problem ? In order to avoid the situation above ,we can use the get to extract the '\n' character. And now it work normally.
  
 1 #include<iostream>
 2 using namespace std;
 3 int main()
 4 {
 5     char fruit[100];
 6     while(cin.getline(fruit,100,'*'))
 7     {
 8         cin.get();
 9         cout<<fruit<<endl;
10     }
11     
12     system("pause");
13 }
14 
   
   One thing you have to remember is that this is a function of the cin.
   there is also a global function getline() in the heder <string>. But you must use string object as parameter instead of c-string.  See the following example. 
   (Reference to :http://www.cplusplus.com/reference/string/getline.html)
  
 1 #include<iostream>
 2 #include<string>
 3 using namespace std;
 4 int main()
 5 {
 6     string s;
 7     getline(cin,s,'*');
 8     cout<<s<<endl;
 9     system("pause");
10 }
11 
    As you can see, the first parameter is istream object on which the extraction operation is performed. The second parameter str is the string object where the extracted content is stored. The Third parameter delim is the delimiting character. The operation of extracting succesive characters is stopped when this delimeter is read. And it will be etracted and discarded. 
   
   
  
  


   
    
    
  
posted on 2007-12-26 17:55 koson 阅读(903) 评论(3)  编辑 收藏 引用 所属分类: C/C++

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# re: About the use of getline() 2007-12-27 12:21 梦在天涯
good , where are you in ?
your english is good!
  回复  更多评论
  

# re: About the use of getline()[未登录] 2007-12-27 12:28 Koson
thx, i'm in guangzhou. Actually, i write this using the reference of the website. But i think this may be a way to improve the written english , despite the content is as simple as that. -_-  回复  更多评论
  

# re: About the use of getline()[未登录] 2007-12-27 14:00 jarod
..... where are u in ?..................

should be

where are u..........  回复  更多评论
  


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