strstr（char * str1，char * str2） [英] strstr(char *str1, char *str2)

问题描述

你好，


我是这个C的新手 - 从来没有 - 我正在尝试搜索字符串

发生子串 - 但是，由于我使用

，因此strstr函数总是返回NULL，所以我不是很成功。但是我知道有一些子字符串存在，因为当我打印出要搜索的字符串

时，我可以用自己的双眼看到它。我添加了函数的代码（resolveResponse）以及我如何
调用此代码 -


调用函数：

- ---

resolveResponse（缓冲区）;

----

缓冲区是这样定义的;

----

char缓冲区[8192];

----


函数调用

----

char * resolveResponse（char * buffer）{

char * endOfResponse; char * startOfFile;


printf（缓冲区）;

endOfResponse = strstr（buffer，" ****"）; / *< ---总是NULL * /

if（endOfResponse == NULL）{

printf（" \ nEnd not found！\ n"） ;

}

startOfFile = endOfResponse + 4;


返回startOfFile;

}


非常感谢你的帮助！

祝你好运Lars

Hi there,

I''m new to this C - never the less - I''m trying to search a string for the
occurence of a substring - However, I''m not very succesful since my use of
the strstr function always returns NULL. But I know that there exsists such
a substring, as I can see it with my own two eye when I print out the string
to be searched. I added the code of the function (resolveResponse)and how I
call this code -

Calling the function:
----
resolveResponse(buffer);
----
buffer is defined this way;
----
char buffer[8192];
----

The Function called
----

char *resolveResponse(char *buffer) {
char *endOfResponse; char *startOfFile;

printf(buffer);

endOfResponse = strstr(buffer, "****"); /* <--- Always NULL */
if(endOfResponse == NULL) {
printf("\nEnd not found!\n");
}
startOfFile = endOfResponse+4;

return startOfFile;
}

Your help is much appreciated!
Best regards Lars

推荐答案

" Lars Langer < 11 ***** @ uwo.caREMOVETHIS>写道：

"Lars Langer" <ll*****@uwo.caREMOVETHIS> writes:

我是这个C的新手 - 从来没有 - 我正在尝试搜索字符串以查找子串的出现 - 但是，我不是自从我使用strstr函数以来非常成功，总是返回NULL。但我知道存在这样的子串，因为当我打印出要搜索的字符串时，我可以用自己的双眼看到它。我添加了函数的代码（resolveResponse）以及我如何调用这段代码 -

调用函数：
----
resolveResponse（buffer）;
----
缓冲区是这样定义的;
----
char buffer [8192];
----
的函数----
char * resolveResponse（char * buffer）{
char * endOfResponse; char * startOfFile;

printf（缓冲区）;

endOfResponse = strstr（buffer，" ****"）; / *< ---始终为NULL * /
if（endOfResponse == NULL）{
printf（" \ nEnd not found！\\\
"）;
}
startOfFile = endOfResponse + 4;

返回startOfFile;
}

I''m new to this C - never the less - I''m trying to search a string for the
occurence of a substring - However, I''m not very succesful since my use of
the strstr function always returns NULL. But I know that there exsists such
a substring, as I can see it with my own two eye when I print out the string
to be searched. I added the code of the function (resolveResponse)and how I
call this code -

Calling the function:
----
resolveResponse(buffer);
----
buffer is defined this way;
----
char buffer[8192];
----

The Function called
----

char *resolveResponse(char *buffer) {
char *endOfResponse; char *startOfFile;

printf(buffer);

endOfResponse = strstr(buffer, "****"); /* <--- Always NULL */
if(endOfResponse == NULL) {
printf("\nEnd not found!\n");
}
startOfFile = endOfResponse+4;

return startOfFile;
}

我们无法知道'是什么'在缓冲区中或者它是如何初始化的。
。如果您的程序正在打印未找到结束！，则

缓冲区不包含****的出现，或其他内容为

出错了。你没有给我们足够的信息来猜测。


如果可以的话，把问题减少到一个小的自包含程序，

我们可以剪切并粘贴并尝试自己。向我们展示修剪过的

程序及其输出。 （你很有可能在这样做的时候自己找到

的问题。）


另外，printf（缓冲区）; "声明可能不安全。 printf（）的第一个

参数是一个格式字符串;如果你的缓冲区包含任何

''％''个字符，printf很可能会尝试打印其他参数

（并且没有）。 />

试试这个：


printf（"％s"，buffer）;


或者这个：


fputs（缓冲区，标准输出）;


-

Keith Thompson（The_Other_Keith） ks *** @ mib.org < http://www.ghoti.net/~kst>

San迭戈超级计算机中心< *> < http://users.sdsc.edu/~kst>

我们必须做点什么。这是事情。因此，我们必须这样做。

We have no way of knowing what''s in "buffer" or how it was
initialized. If your program is printing "End not found!", either
buffer doesn''t contain an occurrence of "****", or something else is
going wrong. You haven''t given us enough information to guess.

If you can, reduce the problem to a small self-contained program,
something we can cut-and-paste and try ourselves. Show us the trimmed
program and its output. (There''s a good chance you''ll find the
problem yourself while doing this.)

Also, the "printf(buffer);" statement is probably unsafe. The first
argument to printf() is a format string; if your buffer contains any
''%'' characters, printf is likely to try to print its other arguments
(and there aren''t any).

Try this:

printf("%s", buffer);

Or this:

fputs(buffer, stdout);

--
Keith Thompson (The_Other_Keith) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

Keith Thompson写道：

Keith Thompson wrote:

fputs（buffer，stdout）;

fputs(buffer, stdout);

或者这个：puts（缓冲区）;

-

Derrick Coetzee

Or this: puts(buffer);
--
Derrick Coetzee

在星期五，2004年9月24日18:13:12 -0400，Lars Langer

< ll ***** @ uwo.caREMOVETHIS>写道：

On Fri, 24 Sep 2004 18:13:12 -0400, "Lars Langer"
<ll*****@uwo.caREMOVETHIS> wrote:

你好，

我是这个C的新手 - 从来没有 - 我正在尝试搜索字符串中的
子串的出现 - 但是，由于我使用strstr函数总是返回NULL，所以我不是很成功。但我知道存在这样的子串，因为当我打印出要搜索的字符串时，我可以用自己的双眼看到它。我添加了函数的代码（resolveResponse）以及我如何调用这段代码 -

调用函数：
----
resolveResponse（buffer）;
----
缓冲区是这样定义的;
----
char buffer [8192];
----
的函数----
char * resolveResponse（char * buffer）{
char * endOfResponse; char * startOfFile;

printf（buffer）;


向我们展示你在这里看到的一个例子。

endOfResponse = strstr（缓冲区，****）; / *< --- Always NULL * /
if（endOfResponse == NULL）{
printf（" \ nEnd not found！\ n"）;


你需要类似

返回NULL;

这里因为如果你在这段代码中下一行不做什么

你期待。

}
startOfFile = endOfResponse + 4;

返回startOfFile;
}

Hi there,

I''m new to this C - never the less - I''m trying to search a string for the
occurence of a substring - However, I''m not very succesful since my use of
the strstr function always returns NULL. But I know that there exsists such
a substring, as I can see it with my own two eye when I print out the string
to be searched. I added the code of the function (resolveResponse)and how I
call this code -

Calling the function:
----
resolveResponse(buffer);
----
buffer is defined this way;
----
char buffer[8192];
----

The Function called
----

char *resolveResponse(char *buffer) {
char *endOfResponse; char *startOfFile;

printf(buffer);
Show us an example of what you see here.

endOfResponse = strstr(buffer, "****"); /* <--- Always NULL */
if(endOfResponse == NULL) {
printf("\nEnd not found!\n");
You need something like
return NULL;
here because if you are in this code the next line does not do what
you expect.
}
startOfFile = endOfResponse+4;

return startOfFile;
}

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