strcpy和strcat问题 [英] strcpy and strcat problem

问题描述

我想将两个字符串组合在一起..并输入另一个字符串。怎么

我可以做。我尝试自己..使用以下代码。但似乎无法得到我想要的

结果..我想得到的结果是c是abcd 。

#include< stdio.h>

#include< string.h>

void main（）{

char a [2] =" ab";

char b [2] =" cd";

char c [4] =" \0" ;;

strcpy（c，a）;

strcat（c，b）;

printf（" a is％ s \ n"，a）;

printf（" b is％s \ nn，b）;

printf（" c is％s \\ \\ n，c）;

}


i只能得到这个结果


a是？b ??

b是??? b ??

c是ab ???? b ??


我的编码有什么问题？有什么不对吗？

请帮忙!!。


谢谢


JC


ps。如果我使用strcpy（c，ab）;和strcat（c，" cd"）;我可以得到结果..c是

abcd"

解决方案

" JC" < [e-mail]>在留言新闻中写道：bl ******** @ rain.i-cable.com ...

我想把两个字符串组合在一起..并且放入另一个字符串。我该怎么办？我尝试自己..使用以下代码。但似乎无法得到我想要的结果..我想得到的结果是c是abcd 。
#include< stdio.h>
#include< string.h>
void main（）{


int main（） {

char a [2] =" ab" ;;


char a [] =" ab";

char b [2] =" cd" ;;


char b [] =" cd";

char c [4] =" \0英寸;


char c [sizeof a + sizeof b + 1] = {0};

strcpy（c，a）;
strcat（c ，b）;
printf（a is％s \ n，a）;
printf（b is％s \ n，b）;
printf（ c是％s \ n，c）;
}
我只得到这个结果

a是吗？b ??
b是??? b ??
c是ab ???? b ??

我的编码有什么问题？


您的阵列没有为字符串终止符提供空间。

有什么不对吗？


是的。未定义的行为。


-Mike

请帮助!!

谢谢

JC

ps。如果我使用strcpy（c，ab）;


好​​到目前为止。文字包含一个终结符。

和strcat（c，cd）;我可以得到结果..c是


不行，来自文字cd的终结符将

写入c [4] - 超出范围 - 未定义

行为。

abcd"

只是偶然。


-Mike

" JC" < [e-mail]>写道：

我想把两个字符串组合在一起..并放入另一个字符串。我该怎么办？我尝试自己..使用以下代码。但似乎无法得到我想要的结果..我想得到的结果是c是abcd 。
#include< stdio.h>
#include< string.h>
void main（）{
未定义的行为，使用：


int main（无效）

{

char a [2] =" ab";
char b [2] =" cd";
char c [4] =" \0英寸;
未定义的行为，你为a，b和c预留了更少的内存。

请记住：" xy"是一个由_three_字符组成的字符串文字，

''x''，''y''和隐式终止''\ 0''。在c的初始值设定项中明确使用''\0''

是不必要的。


char a [3] =" ab" ;;

char b [3] =" cd";

char c [5] =" " ;;


strcpy（c，a）;
strcat（c，b）;
printf（" a is％s \ n"， a）;
printf（b is％s \ nn，b）;
printf（c is％s\ n，c）;
}

我只得到这个结果

一个是？b ??
b是??? b ??
c是ab ???? b？ ？

我的编码有什么问题？有什么不对吗？
请帮助!!

见上文。

ps。如果我使用strcpy（c，ab）;和strcat（c，" cd"）;我可以得到结果..c是
abcd

这只是偶然的，见上文。


问候


Irrwahn

-

错误103：硬盘中死老鼠。

< br>

2003年9月27日星期六00:37:31 + 0800，JC < [e-mail]>写道：

我想将两个字符串组合在一起..并放入另一个字符串。我该怎么办？我尝试自己..使用以下代码。但似乎无法得到我想要的结果..我想得到的结果是c是abcd 。
#include< stdio.h>
#include< string.h>
void main（）{


int main（void ）


main返回一个int。

char a [2] =" ab" ;;


字符串ab实际上有三个字符（''''，''b''和终止NUL

字符''\ 0''），但你只在数组中分配了两个[ ]。


将此更改为


char a [3] =" ab";


或

char a [] =" ab";


在后一种情况下，编译器将为
你。

char b [2] =" cd" ;;
char c [4] =" \0英寸;


同上。


请注意，c []可能只包含三个字符加上终止NUL，所以

你会想要增加分配空间以准备你的字符串

连接如下：


char c [5] =''\'0' ; / * 4个字符+终止NUL * /

strcpy（c，a）;
strcat（c，b）;
printf（a is％s \ n ;，a）;
printf（b is％s \ nn，b）;
printf（c is％s \ n，c）;


返回0;}
ps。如果我使用strcpy（c，ab）;和strcat（c，" cd"）;我可以得到结果..c是
abcd

缓冲区溢出c。


仅仅因为某事是UB，并不意味着UB *的结果有*

与一个人的期望相反。 :-)


-

Robert B. Clark（电子邮件ROT13''ed）

访问ClarkWehyr Enterprises On-Line在 http://www.3clarks.com/ClarkWehyr/

hi,

i want to combine two string together.. and put in to another string. how
can i do . i try myself.. with the follow code. but seem can''t get the
result i want.. i want to get the result with "c is abcd" .
#include <stdio.h>
#include <string.h>
void main() {
char a[2]="ab";
char b[2]="cd";
char c[4]=" \0";
strcpy(c,a);
strcat(c,b);
printf("a is %s\n",a);
printf("b is %s\n",b);
printf("c is %s\n",c);
}

i only get this result

a is b?
b is b?
c is ab?b?

what problem to my coding? anything wrong?
please help!!.

Thanks

JC

ps. if i use strcpy(c,"ab"); and strcat(c,"cd"); i can get the result.."c is
abcd"

解决方案

"JC" <[e-mail]> wrote in message news:bl********@rain.i-cable.com...

hi,

i want to combine two string together.. and put in to another string. how
can i do . i try myself.. with the follow code. but seem can''t get the
result i want.. i want to get the result with "c is abcd" .
#include <stdio.h>
#include <string.h>
void main() {
int main() {
char a[2]="ab";
char a[] = "ab";
char b[2]="cd";
char b[] = "cd";
char c[4]=" \0";
char c[sizeof a + sizeof b + 1] = {0};
strcpy(c,a);
strcat(c,b);
printf("a is %s\n",a);
printf("b is %s\n",b);
printf("c is %s\n",c);
}

i only get this result

a is b?
b is b?
c is ab?b?

what problem to my coding?
Your arrays did not provide room for the string terminators.
anything wrong?
Yes. Undefined behavior.

-Mike
please help!!.

Thanks

JC

ps. if i use strcpy(c,"ab");
OK so far. The literal contains a terminator.
and strcat(c,"cd"); i can get the result.."c is
Not OK, the terminator from the literal "cd" will
be written to c[4] -- out of bounds -- undefined
behavior.
abcd"

Only by accident.

-Mike

"JC" <[e-mail]> wrote:

hi,

i want to combine two string together.. and put in to another string. how
can i do . i try myself.. with the follow code. but seem can''t get the
result i want.. i want to get the result with "c is abcd" . #include <stdio.h>
#include <string.h> void main() { undefined behaviour, use:

int main( void )
{
char a[2]="ab";
char b[2]="cd";
char c[4]=" \0"; Undefined behaviour, you reserved to less memory for a, b and c.
Remember: "xy" is a string literal consisting of _three_ characters,
''x'', ''y'' and the implicit terminating ''\0''. The explicit use of ''\0''
in the initializer for c is unnecessary.

char a[3]="ab";
char b[3]="cd";
char c[5]=" ";

strcpy(c,a);
strcat(c,b);
printf("a is %s\n",a);
printf("b is %s\n",b);
printf("c is %s\n",c);
}

i only get this result

a is b?
b is b?
c is ab?b?

what problem to my coding? anything wrong?
please help!!.
See above.
ps. if i use strcpy(c,"ab"); and strcat(c,"cd"); i can get the result.."c is
abcd"

This worked only by chance, see above.

Regards

Irrwahn
--
ERROR 103: Dead mouse in hard drive.

On Sat, 27 Sep 2003 00:37:31 +0800, "JC" <[e-mail]> wrote:

i want to combine two string together.. and put in to another string. how
can i do . i try myself.. with the follow code. but seem can''t get the
result i want.. i want to get the result with "c is abcd" .
#include <stdio.h>
#include <string.h>
void main() {
int main(void)

main returns an int.
char a[2]="ab";
The string "ab" actually has three chars (''a'', ''b'' and the terminating NUL
character ''\0''), but you''ve only allocated two in array a[].

Change this to

char a[3]="ab";

or
char a[] = "ab";

In the latter case, the compiler will allocate sufficient storage (3) for
you.
char b[2]="cd";
char c[4]=" \0";
Ditto.

Note that c[] may hold only three characters plus the terminating NUL, so
you''ll want to increase the allocated space in preparation for your string
concatenation below:

char c[5] = ''\0''; /* 4 chars + terminating NUL */
strcpy(c,a);
strcat(c,b);
printf("a is %s\n",a);
printf("b is %s\n",b);
printf("c is %s\n",c);
return 0;} ps. if i use strcpy(c,"ab"); and strcat(c,"cd"); i can get the result.."c is
abcd"

Buffer overrun in c.

Just because something is UB, doesn''t mean that the result of that UB *has*
to be counter to one''s expectations. :-)

--
Robert B. Clark (email ROT13''ed)
Visit ClarkWehyr Enterprises On-Line at http://www.3clarks.com/ClarkWehyr/

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