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从www.CppReference.com打包的C++参考手册

    memchr
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  void *memchr( const void *buffer, int ch, size_t count );
</pre>

  <p>The memchr() function looks for the first occurrence of
  <em>ch</em> within <em>count</em> characters in the array pointed to
  by <em>buffer</em>. The return value points to the location of the
  first occurrence of <em>ch</em>, or <strong>NULL</strong> if
  <em>ch</em> isn&#39;t found. For example:</p>
  <pre class="example-code">
   char names[] = &quot;Alan Bob Chris X Dave&quot;;
   if( memchr(names,&#39;X&#39;,strlen(names)) == <strong>NULL</strong> )
     printf( &quot;Didn&#39;t find an X\n&quot; );
   else
     printf( &quot;Found an X\n&quot; );                
</pre>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="memcmp.html">memcmp</a><br>
    <a href="memcpy.html">memcpy</a><br>
    <a href="strstr.html">strstr</a>
  </div>
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<hr>

  <div class="name-format">
    memcmp
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  int memcmp( const void *buffer1, const void *buffer2, size_t count );
</pre>

  <p>The function memcmp() compares the first <em>count</em> characters
  of <em>buffer1</em> and <em>buffer2</em>. The return values are as
  follows:</p>

  <table class="code-table">
    <tr>
      <th class="code-table-th">Value</th>

      <th class="code-table-th">Explanation</th>
    </tr>

    <tr>
      <td class="code-table-td">less than 0</td>

      <td class="code-table-td">buffer1 is less than buffer2</td>
    </tr>

    <tr>
      <td class="code-table-td">equal to 0</td>

      <td class="code-table-td">buffer1 is equal to buffer2</td>
    </tr>

    <tr>
      <td class="code-table-td">greater than 0</td>

      <td class="code-table-td">buffer1 is greater than buffer2</td>
    </tr>
  </table>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="memchr.html">memchr</a><br>
    <a href="memcpy.html">memcpy</a><br>
    <a href="memset.html">memset</a><br>
    <a href="strcmp.html">strcmp</a>
  </div>
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  </table>
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<hr>

  <div class="name-format">
    memcpy
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  void *memcpy( void *to, const void *from, size_t count );
</pre>

  <p>The function memcpy() copies <em>count</em> characters from the
  array <em>from</em> to the array <em>to</em>. The return value of
  memcpy() is <em>to</em>. The behavior of memcpy() is undefined if
  <em>to</em> and <em>from</em> overlap.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="memchr.html">memchr</a><br>
    <a href="memcmp.html">memcmp</a><br>
    <a href="memmove.html">memmove</a><br>
    <a href="memset.html">memset</a><br>
    <a href="strcpy.html">strcpy</a><br>
    <a href="strlen.html">strlen</a><br>
    <a href="strncpy.html">strncpy</a>
  </div>
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  </table>
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<hr>

  <div class="name-format">
    memmove
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  void *memmove( void *to, const void *from, size_t count );
</pre>

  <p>The memmove() function is identical to <a href=
  "memcpy.html">memcpy</a>(), except that it works even if <em>to</em>
  and <em>from</em> overlap.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="memcpy.html">memcpy</a><br>
    <a href="memset.html">memset</a>
  </div>
  </div>
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  </table>
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<hr>

  <div class="name-format">
    memset
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  void* memset( void* buffer, int ch, size_t count );
</pre>

  <p>The function memset() copies <em>ch</em> into the first
  <em>count</em> characters of <em>buffer</em>, and returns
  <em>buffer</em>. memset() is useful for intializing a section of
  memory to some value. For example, this command:</p>

  <pre class="example-code">
   memset( the_array, &#39;\0&#39;, sizeof(the_array) );                
</pre>

  <p>...is a very efficient way to set all values of the_array to
  zero.</p>  

  <p>The table below compares two different methods for initializing
  an array of characters: a for-loop versus memset().  As the size of the
  data being initialized increases, memset() clearly gets the job done
  much more quickly:</p>

  <table class="misc-table">
    <tr class="misc-table-tr-1">
      <th>Input size</th>
      <th>Initialized with a for-loop</th>
      <th>Initialized with memset()</th>
    </tr>

    <tr class="misc-table-tr-2">
      <td>1000</td>
      <td>0.016</td>
      <td>0.017</td>
    </tr>

    <tr class="misc-table-tr-1">
      <td>10000</td>
      <td>0.055</td>
      <td>0.013</td>
    </tr>

    <tr class="misc-table-tr-2">
      <td>100000</td>
      <td>0.443</td>
      <td>0.029</td>
    </tr>

    <tr class="misc-table-tr-1">
      <td>1000000</td>
      <td>4.337</td>
      <td>0.291</td>
    </tr>
  </table>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="memcmp.html">memcmp</a><br>
    <a href="memcpy.html">memcpy</a><br>
    <a href="memmove.html">memmove</a>
  </div>
  </div>
  </td>
  


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  </table>
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<hr>

  <div class="name-format">
    strcat
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  char *strcat( char *str1, const char *str2 );
</pre>

  <p>The strcat() function concatenates <em>str2</em> onto the end of
  <em>str1</em>, and returns <em>str1</em>. For example:</p>
  <pre class="example-code">
   printf( &quot;Enter your name: &quot; );
   scanf( &quot;%s&quot;, name );
   title = strcat( name, &quot; the Great&quot; );
   printf( &quot;Hello, %s\n&quot;, title );            
</pre>

  <p>Note that strcat() does not perform bounds checking, and thus
  risks overrunning <em>str1</em> or <em>str2</em>.  For a similar (and
  safer) function that includes bounds checking, see <a
  href="strncat.html">strncat()</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="strchr.html">strchr</a><br>
    <a href="strcmp.html">strcmp</a><br>
    <a href="strcpy.html">strcpy</a><br>
    <a href="strncat.html">strncat</a>
  </div>

  <p>Another set of related (but non-standard) functions are <a
  href="http://en.wikipedia.org/wiki/Strlcpy">strlcpy and
  strlcat</a>.</p>

  </div>
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  </table>
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<hr>

  <div class="name-format">
    strchr
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  char *strchr( const char *str, int ch );
</pre>

  <p>The function strchr() returns a pointer to the first occurence of
  <em>ch</em> in <em>str</em>, or <strong>NULL</strong> if <em>ch</em>
  is not found.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="strcat.html">strcat</a><br>
    <a href="strcmp.html">strcmp</a><br>
    <a href="strcpy.html">strcpy</a><br>
    <a href="strlen.html">strlen</a><br>
    <a href="strncat.html">strncat</a><br>
    <a href="strncmp.html">strncmp</a><br>
    <a href="strncpy.html">strncpy</a><br>
    <a href="strpbrk.html">strpbrk</a><br>
    <a href="strspn.html">strspn</a><br>
    <a href="strstr.html">strstr</a><br>
    <a href="strtok.html">strtok</a>
  </div>
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  </table>
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<hr>

  <div class="name-format">
    strcmp
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  int strcmp( const char *str1, const char *str2 );
</pre>

  <p>The function strcmp() compares <em>str1</em> and <em>str2</em>,
  then returns:</p>

  <table class="code-table">
    <tr>
      <th class="code-table-th">Return value</th>

      <th class="code-table-th">Explanation</th>
    </tr>

    <tr>
      <td class="code-table-td">less than 0</td>

      <td class="code-table-td">&#39;&#39;str1&#39;&#39; is less than
      &#39;&#39;str2&#39;&#39;</td>
    </tr>

    <tr>
      <td class="code-table-td">equal to 0</td>

      <td class="code-table-td">&#39;&#39;str1&#39;&#39; is equal to
      &#39;&#39;str2&#39;&#39;</td>
    </tr>

    <tr>
      <td class="code-table-td">greater than 0</td>

      <td class="code-table-td">&#39;&#39;str1&#39;&#39; is greater
      than &#39;&#39;str2&#39;&#39;</td>
    </tr>
  </table>

  <p>For example:</p>
  <pre class="example-code">
   printf( &quot;Enter your name: &quot; );
   scanf( &quot;%s&quot;, name );
   if( strcmp( name, &quot;Mary&quot; ) == 0 ) {
     printf( &quot;Hello, Dr. Mary!\n&quot; );
   }        
</pre>

  <p>Note that if <em>str1</em> or <em>str2</em> are missing a
  null-termination character, then strcmp() may not produce valid
  results.  For a similar (and safer) function that includes explicit
  bounds checking, see <a href="strncmp.html">strncmp()</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="memcmp.html">memcmp</a><br>
    <a href="strcat.html">strcat</a><br>
    <a href="strchr.html">strchr</a><br>
    <a href="strcoll.html">strcoll</a><br>
    <a href="strcpy.html">strcpy</a><br>
    <a href="strlen.html">strlen</a><br>
    <a href="strncmp.html">strncmp</a><br>
    <a href="strxfrm.html">strxfrm</a>
  </div>
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  </table>
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<hr>

  <div class="name-format">
    strcoll
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  int strcoll( const char *str1, const char *str2 );
</pre>

  <p>The strcoll() function compares <em>str1</em> and <em>str2</em>,
  much like <a href="strcmp.html">strcmp</a>(). However, strcoll()
  performs the comparison using the locale specified by the (Standard C
  Date &amp; Time) <a href="../stddate/setlocale.html">setlocale</a>()
  function.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    (Standard C Date &amp; Time) <a href=
    "../stddate/setlocale.html">setlocale</a><br>
    <a href="strcmp.html">strcmp</a><br>
    <a href="strxfrm.html">strxfrm</a>
  </div>
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  </table>
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<hr>

  <div class="name-format">
    strcpy
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  char *strcpy( char *to, const char *from );
</pre>

  <p>The strcpy() function copies characters in the string
  <em>from</em> to the string <em>to</em>, including the null
  termination. The return value is <em>to</em>.</p>

  <p>Note that strcpy() does not perform bounds checking, and thus
  risks overrunning <em>from</em> or <em>to</em>.  For a similar (and
  safer) function that includes bounds checking, see <a
  href="strncpy.html">strncpy()</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="memcpy.html">memcpy</a><br>
    <a href="strcat.html">strcat</a><br>
    <a href="strchr.html">strchr</a><br>
    <a href="strcmp.html">strcmp</a><br>
    <a href="strncmp.html">strncmp</a><br>
    <a href="strncpy.html">strncpy</a>
  </div>

  <p>Another set of related (but non-standard) functions are <a
  href="http://en.wikipedia.org/wiki/Strlcpy">strlcpy and
  strlcat</a>.</p>

  </div>
  </td>
  


  </tr>
  </table>
</body></html>
<hr>

  <div class="name-format">
    strcspn
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  size_t strcspn( const char *str1, const char *str2 );
</pre>

  <p>The function strcspn() returns the index of the first character in
  <em>str1</em> that matches any of the characters in
  <em>str2</em>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="strpbrk.html">strpbrk</a><br>
    <a href="strrchr.html">strrchr</a><br>
    <a href="strstr.html">strstr</a><br>
    <a href="strtok.html">strtok</a>
  </div>
  </div>
  </td>
  


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  </table>
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<hr>

  <div class="name-format">
    strerror
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  char *strerror( int num );
</pre>

  <p>The function strerror() returns an implementation defined string
  corresponding to <em>num</em>.</p>
  </div>
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  </table>
</body></html>
<hr>

  <div class="name-format">
    strlen
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;string.h&gt;
  size_t strlen( char *str );
</pre>

  <p>The strlen() function returns the length of <em>str</em>
  (determined by the number of characters before null termination).</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="memcpy.html">memcpy</a><br>
    <a href="strchr.html">strchr</a><br>
    <a href="strcmp.html">strcmp</a><br>
    <a href="strncmp.html">strncmp</a>
  </div>