C 函数 strcpy and memcpy, strdup, memcmp,memset 库函数皆小写

 void *memcpy(void *dst, const void *src, size_t n);

//If copying takes place between objects that overlap, the behavior is undefined

因此标准库提供了地址重叠时的内存拷贝函数：memmove()，

该函数把源字符串拷贝到临时buf里，然后再从临时buf里写到目的地址

 

strcpy   and  memcpy 

memcpy 可以进行指定字节数量的任意类型数据的拷贝， 可以用于内存拷贝。

　　char a[100], b[50];

　　memcpy(b, a,sizeof(b)); //not sizeof(a)，which may cause overflow

strcpy只能用于拷贝字符串，遇到'\0'终止拷贝。

　　char a[100], b[50];

　　strcpy(a,b);

 

void *memset(void *buffer,int c,int count);

把buffer所指内存区域的前count个字节设置成字符c, 一般用于对指定的字符串清零。

 

below from    http://www.cnblogs.com/aprilapril/p/4333173.html

..........strdup("adm"); //as it shows itself, only valid to string type.

memcpy function,return an adress pointed at heap which store"adm"(with string end sign).

.........strcpy(pAim, "4021");
"4021" is copied into the memory started at address pAim.

...........memcpy(void*to,void*from,int size)
copy designated size  to the memory.

..........memcmp(void *a, void *b, int size)

copare two storage, if equal,return to 0,otherwise, get a positive or negative value.

 

estrdup

#include <config.h>
#include <stdlib.h>
#include <err.h>

#include "roken.h"

/*
 * Like strdup but never fails.
 */

ROKEN_LIB_FUNCTION char * ROKEN_LIB_CALL
estrdup (const char *str)
{
    char *tmp = strdup (str);

    if (tmp == NULL)
    errx (1, "strdup failed");
    return tmp;
}