strstr函数的用法_c find函数返回值_strchr函数(5)

如果存在，则返回第一次查找到的字节地址，

不存在，则返回空*/

   pRetval = strrchr((char*)pSrc, 98);
    printf("[%s]-[%d] pRetval = %s \n", __func__, __LINE__, pRetval);

/* 个人理解：在目标字符串中，从字符串开头开始查找对已ASCII码为98的字节，

如果存在，则返回最后一次查找到的字节地址，

不存在，则返回空*/

    return 0;
}
~     

int main (void )
{
    /* 
     * like the strcmp  
     */
    return 0;
} 
~                                                                                                                                                                                
~    

5 strdup

类与字符串拷贝函数，只是需要手动释放返回的字符串地址

int main (void )
{

/* NAME

strdup, strndup - duplicate a string

* SYNOPSIS

#include <string.h>

char *strdup(const char *s);

char *strndup(const char *s, size_t n);

* DESCRIPTION

The strdup() function returns a pointer to a new string which is a duplicate of the string s.

Memory for the new string is obtained with malloc(3), and can be freed with free(3).

The strndup() function is similar, but only copies at most n characters.

If s is longer than n, only n characters are copied, and a terminating null byte ('\0') is added.

* RETURN VALUE

The strdup() function returns a pointer to the duplicated string, or NULL if insufficient memory was available.

*/

 const char *pSrc = "Hello, world!";
    
    char *pRetval = strdup( pSrc );
    printf("[%s]-[%d] pRetval = %s \n", __func__, __LINE__, pRetval);
    /* 复制目标字符串，返回字符串的内存地址需要自己手动释放 */  
    if( pRetval != NULL )
    {
        free( pRetval );
        pRetval = NULL;
    }
    
    pRetval = strndup( pSrc, 4);
    /* 复制指定长度目标字符串，返回字符串的内存地址需要自己手动释放 */  
    printf("[%s]-[%d] pRetval = %s \n", __func__, __LINE__, pRetval);
    if( pRetval != NULL )
    {
        free( pRetval );
        pRetval = NULL;
    }
    
    return 0;
}

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