指向字符串的指針在printf與cout區別

 

根據指針用法: * 定義一個指針， &取變量地址，

 

int b = 1;

 

int *a = &b;

 

則*a =1，但對於字符串而言並不是如此，直接打印指向字符串的指針打印的是地址仍是字符串自己，具體看狀況。

 

定義：

 

char *m1 = "coconut is lovely";  

 

char *m2 = "passion fruit isnice";  

 

char *m3 = "craneberry is fine";  

注：實際聲明應該是const char *m1，緣由char *背後的含義是：給我個字符串，我要修改它，此處應該是要讀取它，具體參考

 

 

測試輸出：

用cout 打印*m1:

 

cout<<"Now use cout to print *m1="<<*m1<<endl;

 

打印輸出：

 

Now use cout to print *m1=c

 

即輸出m1指向字符串的第一個字符。

 

用cout打印m1:

 

cout<<"Now use cout to print m1="<<m1<<endl;

 

輸出：

 

Now use cout to print m1=coconut is lovely

 

即輸出m1所指的內容，而不是m1指向的地址

 

 

用printf打印%c\n", *m1：

 

printf("Now use printf to print *m1=%c\n", *m1);

 

輸出：

 

Now use printf to print *m1=c

 

即爲m1指向的字符串的第一位的內容，但注意是%c而不是%s。由於是字符型，而非字符串型。因此如下表達錯誤: printf("Now use printf to print *m1= %s\n", *m1);

 

用printf 打印 %d m1

 

printf("Now use printf to print m1=%d\n", m1);

 

輸出:

 

Now use printf to print m1=4197112

 

即m1是指針，輸出m1所指向的地址。上面例子中的cout<<m1輸出的是字符串內容。兩者不一致，彷佛反常了。可是咱們能夠使得它們行爲一致。以下:

 

用printf打印%s m1：

 

printf("Now use printf to print m1= %s\n",m1);

 

輸出：

 

Now use printf to print m1= coconut is lovely

 

即m1是指針，輸出m1所指向的地址。使用%s而非%d就能夠使得m1不去表示地址而去表示字符串內容。

 

 

 

完整例子：

#include <stdio.h>
#include <iostream>
using namespace std;

int main()
{
    char *m1 = "coconut is lovely";  
    char *m2 = "passion fruit isnice";  
    char *m3 = "craneberry is fine";
    char* message[3];                   
    int i;                              

    //cout *m1
    cout<<"Now use cout to print *m1="<<*m1<<endl; 
    //cout m1
    cout<<"Now use cout to print m1="<<m1<<endl;
    //cout (int)m1： 64位機char*類型大小位8B，用long轉換
    cout<<"Now use cout to print m1="<<(int)m1<<endl;
    //printf %c *m1
    printf("Now use printf to print *m1=%c\n", *m1); 
    //printf %s *m1
    // printf("Now use printf to print m1= %s\n",*m1); 
    //printf %d m1 
    printf("Now use printf to print m1=%d\n", m1); 
    //printf %s m1
    printf("Now use printf to print m1= %s\n",m1); 
    /*                                       
    message[0] = m1;                    
    message[1] = m2;                    
    message[2] = m3;                    
         
    for (i=0; i<3; i++)  
    printf("%s\n", message[i]); 
    */
}

輸出：

Now use cout to print *m1=c
Now use cout to print m1=coconut is lovely
Now use cout to print m1=4197320
Now use printf to print *m1=c
Now use printf to print m1=4197320
Now use printf to print m1= coconut is lovely

 

 

 

 

 

Ref:

 

1. http://blog.csdn.net/feliciafay/article/details/6818009