blocks|key|2118019|text|void+function+(const+char+*string)
{
+++char+*stringcopy+=+malloc+(1+%2B+strlen+(string));
+++if+(stringcopy)
+++++++strcpy+(stringcopy,+string);
+++else++fprintf+(stderr,+"malloc+failure!"):
+++...
+++do+whatever+needs+to+be+done+with+`stringcopy`
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2118020|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>void function (const char *string)
{
 char *stringcopy = malloc (1 + strlen (string));
 if (stringcopy)
 strcpy (stringcopy, string);
 else fprintf (stderr, "malloc failure!"):
 ...
 do whatever needs to be done with `stringcopy`
}
</code></pre>

blocks|key|5203328|text|为了在C中复制字符串，有一个名为strdup的库函数专门为此而生：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5203329|使用free后，必须释放由strdup分配的内存。|5203330|strdup在一个步骤中提供内存分配和字符串复制操作。如果在某个时间点上要复制的字符串恰好大于数组的大小，则使用char数组可能会出现问题。|5203331|entityMap|0|LINK|mutability|MUTABLE|url|http://linux.die.net/man/3/strdup^0|G|6|G|6|0|0|2|4|D|6|0|0|6|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|G|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]]]

To duplicate strings in C there is a library function called <a href="http://linux.die.net/man/3/strdup"><code>strdup</code></a> made for that:

The memory allocated by <code>strdup</code> must be freed after usage using <code>free</code>.

<code>strdup</code> provides the memory allocation and string copy operation in one step. Using an char array can become problematic if at some point in time the string to copy happens to be larger than the array's size.

blocks|key|5203374|text|您的好友具有以下功能|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5203375|5203376|malloc|unordered-list-item|5203377|memset|5203378|calloc|5203379|memcpy|5203380|strcpy|5203381|strdup|5203382|strncpy|5203383|5203384|但最重要的是，最好的朋友是man+:)|offset|length|style|BOLD|5203385|entityMap^0|0|0|0|0|0|0|0|0|0|0|D|3|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|11|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|12|8|@]|9|@]|A|$]]|$1|F|3|G|5|E|7|13|8|@]|9|@]|A|$]]|$1|H|3|I|5|E|7|14|8|@]|9|@]|A|$]]|$1|J|3|K|5|E|7|15|8|@]|9|@]|A|$]]|$1|L|3|M|5|E|7|16|8|@]|9|@]|A|$]]|$1|N|3|O|5|E|7|17|8|@]|9|@]|A|$]]|$1|P|3|Q|5|E|7|18|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|19|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1A|8|@$U|1B|V|1C|W|X]]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|Z|$]]

Your friends are the following functions

<ul>
<li>malloc</li>
<li>memset</li>
<li>calloc</li>
<li>memcpy</li>
<li>strcpy</li>
<li>strdup</li>
<li>strncpy</li>
</ul>

But best of all, greatest friend is man :)

blocks|key|1533062|text|使用strncpy()。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1533063|void+myfunc(char*+inputstr)
{
++++char+backup[2000];
++++strncpy(backup,+inputstr,+1999);
++++backup[1999]+=+'\0';
}|code-block|syntax|javascript|1533064|将1999个字符复制到2000个字符的数组中，会将最后一个字符留给空终止符。|1533065|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Use strncpy().

<pre><code>void myfunc(char* inputstr)
{
 char backup[2000];
 strncpy(backup, inputstr, 1999);
 backup[1999] = '\0';
}
</code></pre>

Copying 1999 characters to the 2000 character array leaves the last character for the null terminator.

blocks|key|3600569|text|在开始修改之前，您可以使用strcpy来制作字符数组(字符串)的副本。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3600570|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cplusplus.com/reference/clibrary/cstring/strcpy/^0|D|6|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

You can use <a href="http://www.cplusplus.com/reference/clibrary/cstring/strcpy/" rel="nofollow">strcpy</a> to make a copy of your char array (string) before you start modifying.

blocks|key|1533096|text|使用memcpy创建备份。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1533097|char+backup[2000];
char+original[2000];

sprintf(original,+"lovely+data+here");
memcpy(backup,+original,+2000);

char*+orig_ptr+=+original;|code-block|syntax|javascript|1533098|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Use memcpy to create the backup.

<pre><code>char backup[2000];
char original[2000];

sprintf(original, "lovely data here");
memcpy(backup, original, 2000);

char* orig_ptr = original;
</code></pre>

blocks|key|3600669|text|strcpy+reference.|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3600670|strcpy(+backup,+source+);|code-block|syntax|javascript|3600671|来自link的注释。|3600672|3600673|为避免溢出，由目标指向的数组的大小应足够长，以包含与源相同的C字符串(包括终止空字符)，并且不应在内存中与源重叠。|blockquote|3600674|3600675|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cplusplus.com/reference/clibrary/cstring/strcpy/^0|0|H|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@$A|Y|B|Z|1|10]]|C|$]]|$1|D|3|E|5|F|7|11|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|12|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|C|$]]|$1|L|3|M|5|N|7|14|8|@]|9|@]|C|$]]|$1|O|3|-4|5|6|7|15|8|@]|9|@]|C|$]]|$1|P|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|Q|$R|$5|S|T|U|C|$V|W]]]]

<a href="http://www.cplusplus.com/reference/clibrary/cstring/strcpy/" rel="nofollow">strcpy reference.</a> 

<pre><code>strcpy( backup, source );
</code></pre>

Note from link.

<blockquote>
 To avoid overflows, the size of the array pointed by destination shall be long enough to contain the same C string as source (including the terminating null character), and should not overlap in memory with source.
</blockquote>

I have a function that has input and pointer to an array of char in C. in that function I am manipulating the main string, however I want to make a backup copy in another variable before I use it. I want to put it in char backup[2000], so if the pointer changes the backup won't change. 
How can I do that?

copy of a string pointer

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技术创作特训营有奖征文

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有一个函数，它在C中有输入和指向char数组的指针。在这个函数中，我正在操作主字符串，但是在使用它之前，我想在另一个变量中制作一个备份副本。我想把它放在char backup2000中，这样即使指针改变了，备份也不会改变。我该怎么做呢？

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