用strncpy時(shí)字符數(shù)組和字符指針有著怎樣的區(qū)別？#include <iostream>using std::cout;using std::endl;int main(){char ch1[5];char* ch2;char* ch3 = "12345678";strncpy(ch1,ch3,5);//ch1輸出結(jié)果：12345&^% (注：后面幾個(gè)是亂碼)strncpy(ch3,ch2,5);//ch3輸出結(jié)果：12345cout << ch1 <<endl; cout << ch3 <<endl; return 0;}能解釋一下strncpy的運(yùn)行結(jié)果么？？int main(){char ch1[5],ch5[5];char ch2[11],ch6[11];char* ch3 = new char[6];char* ch7 = new char[6];char* ch4 = new char[11];char* ch8 = new char[11];char* ch9 = new char[6];char* ch = "12345678";//strcpy(ch1,ch); cout << 1 << ch1 << endl;//strcpy(ch2,ch); cout << 2 << ch2 << endl;//strcpy(ch3,ch); cout << 3 << ch3 << endl;//strcpy(ch4,ch); cout << 4 << ch4 << endl; //上面四行結(jié)果均是12345678strncpy(ch5,ch,5); cout << 5 << ch5 << endl; //512345后面亂碼strncpy(ch6,ch,5); cout << 6 << ch6 << endl; //612345后面亂碼strncpy(ch7,ch,5); cout << 7 << ch7 << endl; //712345后亂碼strncpy(ch7,ch,6); cout << 7 << ch7 << endl; //7123456后亂碼strncpy(ch8,ch,5); cout << 8 << ch8 << endl; //812345后面亂碼strncpy(ch9,ch,5); cout << 9 << ch9 << endl; //912345后面亂碼system("pause");return 0;}
2 回答
大話西游666
TA貢獻(xiàn)1817條經(jīng)驗(yàn) 獲得超14個(gè)贊
操作字串時(shí)，不要忘了給最后的'\0'分配空間，不然輸出時(shí)就會(huì)帶著亂碼，正確的做法是：
char *ch2 = new char[6];
strncpy(ch2, ch3, 5);
ch2[5] = '\0';
cout << ch2 << endl;
不能少了這句
delete[] ch2;
之所以出現(xiàn)亂碼，是因?yàn)閳?zhí)行strncpy的過(guò)程中并沒(méi)有將字串結(jié)束符'\0'賦值給目標(biāo)，目標(biāo)字串沒(méi)有結(jié)束符輸出時(shí)自然就不知道應(yīng)該什么時(shí)候停止輸出，除非遇到'\0'字符,因此你會(huì)看到亂碼，就這樣。
慕的地10843
TA貢獻(xiàn)1785條經(jīng)驗(yàn) 獲得超8個(gè)贊
分析下strncpy的源代碼應(yīng)該就明白了 ，庫(kù)函數(shù)并沒(méi)有對(duì)dest檢查，有可能dest不是以'\0'結(jié)尾， 輸出的時(shí)候就會(huì)出錯(cuò)了
char * __cdecl strncpy (
char * dest,
const char * source,
size_t count
)
{
char *start = dest;
while (count && (*dest++ = *source++)) /* copy string */
count--;
if (count) /* pad out with zeroes */
while (--count)
*dest++ = '\0';
return(start);
}
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