devdocs/c/string%2Fbyte%2Fstrcspn.html


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    <h1 id="firstHeading" class="firstHeading">strcspn</h1>            <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code>&lt;string.h&gt;</code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl"> <td class="t-dcl-nopad"> <pre data-language="c">size_t strcspn( const char *dest, const char *src );</pre>
</td> <td class="t-dcl-nopad"> </td> <td class="t-dcl-nopad"> </td> </tr>  </table> <p>Returns the length of the maximum initial segment of the null-terminated byte string pointed to by <code>dest</code>, that consists of only the characters <i>not</i> found in the null-terminated byte string pointed to by <code>src</code>.</p>
<p>The behavior is undefined if either <code>dest</code> or <code>src</code> is not a pointer to a null-terminated byte string.</p>
<h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> dest </td> <td> - </td> <td> pointer to the null-terminated byte string to be analyzed </td>
</tr> <tr class="t-par"> <td> src </td> <td> - </td> <td> pointer to the null-terminated byte string that contains the characters to search for </td>
</tr>
</table> <h3 id="Return_value"> Return value</h3> <p>The length of the maximum initial segment that contains only characters not found in the null-terminated byte string pointed to by <code>src</code></p>
<h3 id="Notes"> Notes</h3> <p>The function name stands for "complementary span" because the function searches for characters not found in <code>src</code>, that is the complement of <code>src</code>.</p>
<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include &lt;string.h&gt;
#include &lt;stdio.h&gt;
 
int main(void)
{
    const char *string = "abcde312$#@";
    const char *invalid = "*$#";
 
    size_t valid_len = strcspn(string, invalid);
    if(valid_len != strlen(string))
       printf("'%s' contains invalid chars starting at position %zu\n",
               string, valid_len);
}</pre></div> <p>Output:</p>
<div class="text source-text"><pre data-language="c">'abcde312$#@' contains invalid chars starting at position 8</pre></div> </div> <h3 id="References"> References</h3>  <ul>
<li> C11 standard (ISO/IEC 9899:2011): </li>
<ul><li> 7.24.5.3 The strcspn function (p: 368) </li></ul>
<li> C99 standard (ISO/IEC 9899:1999): </li>
<ul><li> 7.21.5.3 The strcspn function (p: 331) </li></ul>
<li> C89/C90 standard (ISO/IEC 9899:1990): </li>
<ul><li> 4.11.5.3 The strcspn function </li></ul>
</ul>         <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="strspn" title="c/string/byte/strspn"> <span class="t-lines"><span>strspn</span></span></a></div> </td> <td> returns the length of the maximum initial segment that consists <br> of only the characters found in another byte string <br> <span class="t-mark">(function)</span>  </td>
</tr> <tr class="t-dsc"> <td> <div><a href="../wide/wcscspn" title="c/string/wide/wcscspn"> <span class="t-lines"><span>wcscspn</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c95">(C95)</span></span></span></div> </td> <td> returns the length of the maximum initial segment that consists <br> of only the wide chars <i>not</i> found in another wide string <br> <span class="t-mark">(function)</span>  </td>
</tr> <tr class="t-dsc"> <td> <div><a href="strpbrk" title="c/string/byte/strpbrk"> <span class="t-lines"><span>strpbrk</span></span></a></div> </td> <td> finds the first location of any character in one string, in another string <br> <span class="t-mark">(function)</span>  </td>
</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/string/byte/strcspn" title="cpp/string/byte/strcspn">C++ documentation</a></span> for <code>strcspn</code> </td>
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