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鍏充簬C++涓殑const鍏抽敭瀛楃殑鐢ㄦ硶闈炲父鐏墊椿錛岃屼嬌鐢╟onst灝嗗ぇ澶ф敼鍠勭▼搴忕殑鍋ュ．鎬с傚湪緗戜笂鎼滃鐩稿叧涓婚錛屽彂鐜板ぇ澶氭暟鏂囩珷闆峰悓錛岃屽叧閿湴鏂瑰茍涓嶆槸寰堟竻妤氥傚湪緗戠粶璧勬枡錛屽弬鑰冧功鐨勫熀紜涓婏紝緇撳悎鏈漢鐨勪竴浜涗綋浼氭葷粨濡備笅錛屾湡鏈涘澶у鏈夋墍甯姪錛?br />
涓 const鍩虹 涓嬮潰鍥涗釜瀹氫箟璇彞鏄ぇ澶氭暟涔︾睄璁茶Вconst鍏抽敭瀛楅兘浼氱敤鍒扮殑錛?br /> [1]const int* a = &b; [2]int const *a = &b; [3]int* const a = &b; [4]const int* const a = &b; 濡傛灉浣犺兘鍖哄垎鍑轟笂榪板洓縐嶆儏鍐碉紝璇佹槑浣犲熀紜涓嶉敊錛屼笉榪囦篃涓嶈楂樺叴澶棭錛岃繖涓彧鏄渶鍩虹鐨勯儴鍒嗕簡銆備笉鐭ラ亾涔熷緢瀹規槗錛氬鏋渃onst浣嶄簬鏄熷彿鐨勫乏渚э紙涓嶇const鍦ㄧ被鍨嬩慨楗扮鐨勫乏榪樻槸鍙籌級錛屽垯const灝辨槸鐢ㄦ潵淇グ鎸囬拡鎵鎸囧悜鐨勫彉閲忥紝鍗蟲寚閽堟寚鍚戜負甯擱噺錛涘鏋渃onst浣嶄簬鏄熷彿鐨勫彸渚э紝const灝辨槸淇グ鎸囬拡鏈韓錛屽嵆鎸囬拡鏈韓鏄父閲忋俒1]鍜孾2]鐨勬儏鍐電浉鍚岋紝閮芥槸鎸囬拡鎵鎸囧悜鐨勫唴瀹逛負甯擱噺錛岃繖縐嶆儏鍐典笅涓嶅厑璁稿鍐呭榪涜鏇存敼鎿嶄綔錛屽涓嶈兘*a = 3 錛涜繖鏍風殑涓縐嶅０鏄庢柟寮忕殑浣滅敤鏄彲浠ヤ慨鏀筽i榪欎釜鎸囬拡鎵鎸囧悜鐨勫唴瀛樺湴鍧鍗翠笉鑳戒慨鏀規寚鍚戝璞＄殑鍊鹼紱[3]涓烘寚閽堟湰韜槸甯擱噺錛岃屾寚閽堟墍鎸囧悜鐨勫唴瀹逛笉鏄父閲忥紝榪欑鎯呭喌涓嬩笉鑳藉鎸囬拡鏈韓榪涜鏇存敼鎿嶄綔錛屽a++鏄敊璇殑;[4]涓烘寚閽堟湰韜拰鎸囧悜鐨勫唴瀹瑰潎涓哄父閲忋?br /> 鍙﹀const 鐨勪竴浜涘己澶х殑鍔熻兘鍦ㄤ簬瀹冨湪鍑芥暟澹版槑涓殑搴旂敤銆傚湪涓涓嚱鏁板０鏄庝腑錛宑onst 鍙互淇グ鍑芥暟鐨勮繑鍥炲鹼紝鎴栨煇涓弬鏁幫紱瀵逛簬鎴愬憳鍑芥暟錛岃繕鍙互淇グ鏄暣涓嚱鏁般傛湁濡備笅鍑犵鎯呭喌錛屼互涓嬩細閫愭笎鐨勮鏄庣敤娉曪細 A_class& operator=(const A_class& a); //A_class 涓轟竴涓凡緇忓畾涔夌殑綾伙紝涓嬫枃鍚?br /> void fun0(const A_class* a ); void fun1( ) const; // fun1( ) 涓虹被鎴愬憳鍑芥暟 const A_class fun2( ); 浜?const鐨勫垵濮嬪寲 鍏堢湅涓涓媍onst鍙橀噺鍒濆鍖栫殑鎯呭喌 1) 闈炴寚閽坈onst甯擱噺鍒濆鍖栫殑鎯呭喌錛?br /> A_class b; const A_class a = b; 2) 鎸囬拡(寮曠敤)const甯擱噺鍒濆鍖栫殑鎯呭喌錛?br /> A_class* d = new A_class(); const A_class* c = d; 鎴栬? const A_class* c = new A_class(); 寮曠敤錛? A_class f; const A_class& e = f; // 榪欐牱浣渆鍙兘璁塊棶澹版槑涓篶onst鐨勫嚱鏁幫紝鑰屼笉鑳借闂竴鑸殑鎴愬憳鍑芥暟錛?br /> [鎬濊?]錛?浠ヤ笅鐨勮繖縐嶈祴鍊兼柟娉曟紜悧錛?br /> const A_class* c=new A_class(); A_class* e = c; 榪欑鏂規硶涓嶆紜紝鍥犱負澹版槑鎸囬拡鐨勭洰鐨勬槸涓轟簡瀵瑰叾鎸囧悜鐨勫唴瀹硅繘琛屾敼鍙橈紝鑰屽０鏄庣殑鎸囬拡e鎸囧悜鐨勬槸涓涓父閲忥紝鎵浠ヤ笉姝ｇ‘錛?br /> [鎬濊?]錛?浠ヤ笅鐨勮繖縐嶈祴鍊兼柟娉曟紜悧錛?br /> A_class* const c = new A_class(); A_class* b = c; 榪欑鏂規硶姝ｇ‘錛屽洜涓哄０鏄庢寚閽堟墍鎸囧悜鐨勫唴瀹瑰彲鍙橈紱 涓?浣滀負鍙傛暟鍜岃繑鍥炲肩殑const淇グ絎?br /> 鍏跺疄錛屼笉璁烘槸鍙傛暟榪樻槸榪斿洖鍊鹼紝閬撶悊閮芥槸涓鏍風殑錛屽弬鏁頒紶鍏ユ椂鍊欏拰鍑芥暟榪斿洖鐨勬椂鍊欙紝鍒濆鍖朿onst鍙橀噺 1 淇グ鍙傛暟鐨刢onst,濡? void fun0(const A_class* a ); void fun1(const A_class& a); 璋冪敤鍑芥暟鐨勬椂鍊欙紝鐢ㄧ浉搴旂殑鍙橀噺鍒濆鍖朿onst甯擱噺錛屽垯鍦ㄥ嚱鏁頒綋涓紝鎸夌収const鎵淇グ鐨勯儴鍒嗚繘琛屽父閲忓寲錛屽褰㈠弬涓篶onst A_class* a錛屽垯涓嶈兘瀵逛紶閫掕繘鏉ョ殑鎸囬拡鐨勫唴瀹硅繘琛屾敼鍙橈紝淇濇姢浜嗗師鎸囬拡鎵鎸囧悜鐨勫唴瀹癸紱濡傚艦鍙備負const A_class& a錛屽垯涓嶈兘瀵逛紶閫掕繘鏉ョ殑寮曠敤瀵硅薄榪涜鏀瑰彉錛屼繚鎶や簡鍘熷璞＄殑灞炴с?br /> [娉ㄦ剰]錛氬弬鏁癱onst閫氬父鐢ㄤ簬鍙傛暟涓烘寚閽堟垨寮曠敤鐨勬儏鍐? 2 淇グ榪斿洖鍊肩殑const錛屽, const A_class fun2( ); const A_class* fun3( ); 榪欐牱澹版槑浜嗚繑鍥炲煎悗錛宑onst鎸夌収"淇グ鍘熷垯"榪涜淇グ錛岃搗鍒扮浉搴旂殑淇濇姢浣滅敤銆?br /> const Rational operator*(const Rational& lhs, const Rational& rhs) { return Rational(lhs.numerator() * rhs.numerator(), lhs.denominator() * rhs.denominator()); } 榪斿洖鍊肩敤const淇グ鍙互闃叉榪欐牱鐨勬搷浣滃彂鐢? Rational a,b; Radional c; (a*b) = c; 涓鑸敤const淇グ榪斿洖鍊間負瀵硅薄鏈韓錛堥潪寮曠敤鍜屾寚閽堬級鐨勬儏鍐靛鐢ㄤ簬浜岀洰鎿嶄綔絎﹂噸杞藉嚱鏁板茍浜х敓鏂板璞＄殑鏃跺欍?br /> [鎬葷粨]涓鑸儏鍐典笅錛屽嚱鏁扮殑榪斿洖鍊間負鏌愪釜瀵硅薄鏃訛紝濡傛灉灝嗗叾澹版槑涓篶onst鏃訛紝澶氱敤浜庢搷浣滅鐨勯噸杞姐?br /> 閫氬父錛屼笉寤鴻鐢╟onst淇グ鍑芥暟鐨勮繑鍥炲肩被鍨嬩負鏌愪釜瀵硅薄鎴栧鏌愪釜瀵硅薄寮曠敤鐨勬儏鍐點?br /> 鍘熷洜濡備笅錛氬鏋滆繑鍥炲間負鏌愪釜瀵硅薄涓篶onst錛坈onst A_class test = A_class 瀹炰緥錛夋垨鏌愪釜瀵硅薄鐨勫紩鐢ㄤ負const錛坈onst A_class& test = A_class瀹炰緥錛夛紝鍒欒繑鍥炲煎叿鏈塩onst灞炴э紝鍒欒繑鍥炲疄渚嬪彧鑳借闂被A_class涓殑鍏湁錛堜繚鎶わ級鏁版嵁鎴愬憳鍜宑onst鎴愬憳鍑芥暟錛屽茍涓斾笉鍏佽瀵瑰叾榪涜璧嬪兼搷浣滐紝榪欏湪涓鑸儏鍐典笅寰堝皯鐢ㄥ埌銆?br /> [鎬濊?]錛?榪欐牱瀹氫箟璧嬪兼搷浣滅閲嶈澆鍑芥暟鍙互鍚楋紵 const A_class& operator=(const A_class& a); 涓嶆紜紱鍦╟onst A_class::operator=(const A_class& a)涓紝鍙傛暟鍒楄〃涓殑const鐨勭敤娉曟紜紝鑰屽綋榪欐牱榪炵畫璧嬪肩殑鏃朵警錛岄棶棰樺氨鍑虹幇浜嗭細A_class a,b,c:(a=b)=c;鍥犱負a.operator=(b)鐨勮繑鍥炲兼槸瀵筧鐨刢onst寮曠敤錛屼笉鑳藉啀灝哻璧嬪肩粰const甯擱噺銆?br /> 鍥?綾繪垚鍛樺嚱鏁頒腑const鐨勪嬌鐢?br /> 涓鑸斁鍦ㄥ嚱鏁頒綋鍚庯紝褰㈠錛?br /> void fun() const; 濡傛灉涓涓垚鍛樺嚱鏁扮殑涓嶄細淇敼鏁版嵁鎴愬憳錛岄偅涔堟渶濂藉皢鍏跺０鏄庝負const錛屽洜涓篶onst鎴愬憳鍑芥暟涓笉鍏佽瀵規暟鎹垚鍛樿繘琛屼慨鏀癸紝濡傛灉淇敼錛岀紪璇戝櫒灝嗘姤閿欙紝榪欏ぇ澶ф彁楂樹簡紼嬪簭鐨勫仴澹с?br /> 浜?浣跨敤const鐨勪竴浜涘緩璁?br /> 1 瑕佸ぇ鑳嗙殑浣跨敤const錛岃繖灝嗙粰浣犲甫鏉ユ棤灝界殑鐩婂錛屼絾鍓嶆彁鏄綘蹇呴』鎼炴竻妤氬師濮旓紱 2 瑕侀伩鍏嶆渶涓鑸殑璧嬪兼搷浣滈敊璇紝濡傚皢const鍙橀噺璧嬪鹼紝鍏蜂綋鍙鎬濊冮錛?br /> 3 鍦ㄥ弬鏁頒腑浣跨敤const搴旇浣跨敤寮曠敤鎴栨寚閽堬紝鑰屼笉鏄竴鑸殑瀵硅薄瀹炰緥錛屽師鍥犲悓涓婏紱 4 const鍦ㄦ垚鍛樺嚱鏁頒腑鐨勪笁縐嶇敤娉曪紙鍙傛暟銆佽繑鍥炲箋佸嚱鏁幫級瑕佸緢濂界殑浣跨敤錛?br /> 5 涓嶈杞繪槗鐨勫皢鍑芥暟鐨勮繑鍥炲肩被鍨嬪畾涓篶onst;6闄や簡閲嶈澆鎿嶄綔絎﹀涓鑸笉瑕佸皢榪斿洖鍊肩被鍨嬪畾涓哄鏌愪釜瀵硅薄鐨刢onst寮曠敤; |
#include "string.h"
#include "Decode.h"
#pragma argsused
typedef int (__stdcall *fun_AddFun)(int Data);
HINSTANCE gLib = NULL;
fun_AddFun gFun = NULL;
int WINAPI DllEntryPoint(HINSTANCE hinst, unsigned long reason, void* lpReserved){
switch(reason) {
case DLL_PROCESS_ATTACH: {
char tPath[255];
int tSize;
GetModuleFileName(hinst,tPath,255);
tSize = strlen(tPath)-1;
while(tPath[tSize]!='\\') {
--tSize;
}
tPath[tSize+1] = 0;
strcat(tPath,"Test.dll");
gLib = LoadLibrary(tPath);
if(gLib == NULL) {
MessageBox(NULL,tPath,"Load Library Failed",MB_OK);
return;
}
gFun = (fun_AddFun)GetProcAddress(gLib,"AddFun");
}
break;
case DLL_PROCESS_DETACH: {
if(gLib) {
FreeLibrary(gLib);
gLib = NULL;
}
}
break;
}
return 1;
}
JNIEXPORT jint JNICALL Java_Encode_Add (JNIEnv *env, jclass cls, jint a, jint b) {
if(gFun==NULL)
return 0;
else {
int tRe = gFun(100);
return a + b + tRe;
}
}
int __declspec(dllexport) __stdcall fun_x(int a,int b)
{
if(gFun==NULL)
return 0;
else {
int tRe = gFun(100);
return a + b + tRe;
}
}
2.鍦↙inker閫夐」涓幓闄se dynamic RTL閫夐」
3.鍦―irectories/conditionals涓夋嫨include path娣誨姞java鐨刬nclude鍜寃in鐩綍
#include <cstdlib>
#include <fstream>
#include <stdio.h>
using namespace std;
int main(int argc, char *argv[])
{
char* str = "e:/test/nihao.txt";
FILE *t = fopen(str,"wb+");
char tbuf[10]={0};
fwrite(tbuf,1,100,t);
fclose(t);
system("PAUSE");
return EXIT_SUCCESS;
}
FILE *tIn = fopen(szStr,"rb");
if (tIn == NULL) {
cout<<"鏂囦歡涓嶈兘鎵撳紑!";
return NULL;
}
fseek(tIn, 0, SEEK_END);
int tSize = ftell(tIn);
fseek(tIn, 0, SEEK_SET);
char *tBuf = new char[tSize];
fread(tBuf,tSize,1,tIn);
fclose(tIn);
#include <stdio.h>
int main()
{
unsigned int eflags1, eflags2 = 0;
unsigned int eax = 0;
unsigned int ebx,ecx,edx;
/**
* 嫻嬭瘯CPU鏄惁鏀寔CPUID鎸囦護銆?br />
* eflags瀵勫瓨鍣ㄧ殑絎?1浣嶏紝濡傛灉紼嬪簭鍙互娓呮/璁劇疆瀹冿紝鍒欒鏄嶤PU鏀寔CPUID鎸囦護銆傚惁鍒欎笉鏀寔
*/
/* 鍏堝彇eflags */
asm volatile ("pushf\n\t"
"popl %%eax"
: "=a"(eflags1)
:
: "memory"
);
printf("original eflags is %p\n", eflags1);
/* 鎶奺flags鐨勭21浣嶅彇鍙嶏紝鍐欏洖瀵勫瓨鍣ㄤ腑 */
asm volatile ("pushl %0\n\t"
"popf"
:
: "g"(eflags1 & ~( eflags1 & (1<<21) ) )
);
/* 媯鏌ヤ竴涓嬬幇鍦ㄧ殑eflags錛岀‘璁ょ21浣嶅拰鏈鍒濈殑鍊肩浉鍙?*/
asm volatile ("pushf\n\t"
"popl %%eax"
: "=a"(eflags2)
:
: "memory"
);
printf("modified eflags is %p\n", eflags2);
/* 鎶婂師鏉ョ殑eflags鍊艱緗洖鍘?*/
asm volatile ("pushl %0\n\t"
"popf"
:
: "g"(eflags1)
);
/**
* FIXME: Intel鏂囨。騫舵病鏈夎錛屽鏋滀笉鏀寔CPUID鐨勮瘽錛宑lear/set eflags鐨勭21浣嶄細鏈変粈涔堥敊璇?br />
* 瀹冨彧璇達紝鍦ㄤ笉鏀寔CPUID鎸囦護鐨凜PU涓婏紝濡?0386錛屾墽琛孋PUID浼氫駭鐢焛nvalid opcode閿欒
*
* 鎵浠ワ紝鍦ㄨ繖閲屾垜浠笉澶勭悊 璇?鍐?eflags 絎?1姣旂壒澶辮觸鐨勬儏褰?br />
*/
/**
* eax == 1錛屽垯鍦╡ax涓繑鍥濬amily/Model/Stepping絳変俊鎭?br />
* [0:3] stepping
* [4:7] model
* [8:11] family
* [12:13] processor type
* [16:19] extended model ID
* [20:27] extended family ID
*/
asm volatile ("cpuid"
: "=a"(eax)
: "0"(1)
);
// printf("eax is %p\n", eax);
printf("Extended Family\t: %d\n", (0xff00000 & eax) >> 20);
printf("Extended Model\t: %d\n", (0xf0000 & eax) >> 16);
printf("Processor type\t: %d\n", (0x3000 & eax) >> 12);
printf("Family\t\t: %d\n", (0xf00 & eax) >> 8);
printf("Model\t\t: %d\n", (0xf0 & eax) >> 4);
printf("Stepping:\t: %d\n", (0xf & eax));
printf("\n");
/**
* eax == 0x800000000
* 濡傛灉CPU鏀寔Brand String錛屽垯鍦‥AX涓繑 >= 0x80000004鐨勫箋?br />
*/
asm volatile ("cpuid"
: "=a"(eax)
: "0"(0x80000000)
);
printf("Is CPU support Brand String? %s\n", eax >= 0x80000004? "yes":"no");
printf("\n");
/**
* 濡傛灉鏀寔Brand String錛屽垯EAX浠?x80000002鍒?x80000004錛屾瘡嬈″1錛孋PUID鎸囦護榪斿洖錛?br />
* EAX : Processor Brand String
* EBX : Processor Brand String Continued
* ECX : Processor Brand String Continued
* EDX : Processor Brand String Continued
*/
if(eax >= 0x80000004) {
unsigned int brands[4]; //姣忔鐨別ax銆乪bx銆乪cx銆乪dx
unsigned int i;
printf("Brand String\t: ");
for (i = 0x80000002; i <= 0x80000004; i++) {
asm volatile ("cpuid"
: "=a"(brands[0]), "=b"(brands[1]), "=c"(brands[2]), "=d"(brands[3])
: "0" (i)
);
printf("%s", (char *)brands);
}
//FIXME: 鎵撳嚭鏉ョ殑瀛楃涓叉槸錛欼n^Htel(R) Pentium(R^H) D CPU 2.80GHz
//鍏朵腑^H鏄釜涓嶅彲瑙佸瓧絎︼紝浼氭妸瀹冨墠涓涓悆鎺?/p>
printf("\n");
}
/**
* eax == 0
* eax : cpuid鎸囦護鍏佽鐨勬渶澶ax杈撳叆鍊?br />
* ebx : "Genu"
* ecx : "ntel"
* edx : "inel"
*/
asm volatile ("cpuid"
: "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)
: "0"(0) );
printf("Maximum CPUID Input EAX : %p\n", eax);
char string[128];
snprintf(string, 5, "%s", (char *)&ebx);
snprintf(string + 4, 5, "%s", (char *)&edx);
snprintf(string + 8, 5, "%s", (char *)&ecx);
printf("Vendor\t\t: %s\n", string);
printf("\n");
/**
* eax == 1,
* edx鐨勭18姣旂壒涓?錛屽垯CPU鏀寔serial number
* 涓?錛屽垯涓嶆敮鎸侊紝鎴栬呰disabled
* 搴忓垪鍙鋒湁96浣嶏紝鍏朵腑鏈楂?2浣嶅嵆鏄痚ax鐨勮緭鍑哄箋傚簲褰撴妸瀹冧繚瀛樹笅鏉ワ紝鐒跺悗
* 鍐嶈緗甧ax==3, 鍙栧墿涓嬬殑64浣?br />
*/
asm volatile ("cpuid"
: "=a"(eax), "=d"(edx)
: "a"(1)
);
if ( edx & (1 << 18) ) {
/* serial number supported */
/* edx杈撳嚭涓棿32浣嶇殑搴忓垪鍙鳳紝ecx杈撳嚭鏈浣?2浣嶇殑搴忓垪鍙?*/
asm volatile ("cpuid"
: "=c"(ecx), "=d"(edx)
: "a"(3)
);
printf("Serial Number\t : %x-%x-%x-%x-%x-%x\n",
eax >> 16, eax << 16, edx >> 16, edx << 16, ecx >> 16, ecx << 16);
} else
printf("Serial Number not supported.\n");
printf("\n");
/**
* eax == 80000006h錛岃繑鍥濴2 Cache鐨勪俊鎭?br />
*
* ecx[31:16] : L2 Cache size, in Kbytes
* ecx[15:12] : L2 Cache Associativity
* 00h disabled
* 01h direct mapped
* 02h 2-Way
* 04h 4-Way
* 06h 8-Way
* 08h 16-Way
* 0Fh Fully associative
* ecx[7:0] : L2 Cache Line size in bytes
*/
asm volatile ("cpuid"
: "=c"(ecx)
: "a"(0x80000006)
);
printf("L2 Cache Size\t : %dKbytes\n", ( ecx >> 16 ) );
printf("L2 Cache Line Size\t : %dbytes\n", (ecx & 0xff));
printf("L2 Cache Associativity\t : ");
switch ( (ecx & 0xf000) >> 12 )
{
case 0x00:
printf("%s\n", "disabled");
break;
case 0x01:
printf("%s\n", "direct mapped");
break;
case 0x02:
printf("%s\n", "2-Way");
break;
case 0x04:
printf("%s\n", "4-Way");
break;
case 0x06:
printf("%s\n", "8-Way");
break;
case 0x08:
printf("%s\n", "16-Way");
break;
case 0x0f:
printf("Fully associative");
break;
default:
printf("No such entry...\n");
}
printf("\n");
/**
* Input : eax == 4 && ecx == 0
*
* (eax[31:26] + 1) 鏄鐗╃悊澶勭悊鍣╬ackage涓婂疄鐜扮殑core CPUs鏁扮洰
*/
asm volatile ("cpuid"
: "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)
: "0"(4), "2"(0)
);
printf("Number of Cores on this physical package\t : %d\n", (eax >> 27) + 1 );
printf("\n");
/**
* Input : eax == 1錛屽垯edx榪斿洖feature flag
*
*/
return 0;
}
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <net/if.h>
#include <string.h>
int main(int argc, char *argv[]){
struct ifreq ifreq;
int sock;
if(argc!=2)
{
printf("Usage : ethname\n");
return 1;
}
if((sock=socket(AF_INET,SOCK_STREAM,0))<0)
{
perror("socket");
return 2;
}
strcpy(ifreq.ifr_name,argv[1]);
if(ioctl(sock,SIOCGIFHWADDR,&ifreq)<0)
{
perror("ioctl");
return 3;
}
printf("%02x:%02x:%02x:%02x:%02x:%02x\n",
(unsigned char)ifreq.ifr_hwaddr.sa_data[0],
(unsigned char)ifreq.ifr_hwaddr.sa_data[1],
(unsigned char)ifreq.ifr_hwaddr.sa_data[2],
(unsigned char)ifreq.ifr_hwaddr.sa_data[3],
(unsigned char)ifreq.ifr_hwaddr.sa_data[4],
(unsigned char)ifreq.ifr_hwaddr.sa_data[5]);
unsigned char temp = (unsigned char)ifreq.ifr_hwaddr.sa_data[0];
int a = temp;
printf("%02x",a);
return 0;
}