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<h1 id="firstHeading" class="firstHeading">strtoul, strtoull</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><stdlib.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-until-c99"> <td><pre data-language="c">unsigned long strtoul( const char *str, char **str_end,
int base );</pre></td> <td class="t-dcl-nopad"> </td> <td><span class="t-mark-rev t-until-c99">(until C99)</span></td> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">unsigned long strtoul( const char *restrict str, char **restrict str_end,
int base );</pre>
</td> <td class="t-dcl-nopad"> </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">unsigned long long strtoull( const char *restrict str, char **restrict str_end,
int base );</pre>
</td> <td class="t-dcl-nopad"> </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> </table> <p>Interprets an unsigned integer value in a byte string pointed to by <code>str</code>.</p>
<p>Discards any whitespace characters (as identified by calling <a href="isspace" title="c/string/byte/isspace"><code>isspace</code></a>) until the first non-whitespace character is found, then takes as many characters as possible to form a valid <i>base-n</i> (where n=<code>base</code>) unsigned integer number representation and converts them to an integer value. The valid unsigned integer value consists of the following parts:</p>
<ul>
<li> <span class="t-mark">(optional)</span> plus or minus sign </li>
<li> <span class="t-mark">(optional)</span> prefix (<code>0</code>) indicating octal base (applies only when the base is <code>8</code> or <code>0</code>) </li>
<li> <span class="t-mark">(optional)</span> prefix (<code>0x</code> or <code>0X</code>) indicating hexadecimal base (applies only when the base is <code>16</code> or <code>0</code>) </li>
<li> a sequence of digits </li>
</ul> <p>The set of valid values for base is <code>{0,2,3,...,36}.</code> The set of valid digits for base-<code>2</code> integers is <code>{0,1},</code> for base-<code>3</code> integers is <code>{0,1,2},</code> and so on. For bases larger than <code>10</code>, valid digits include alphabetic characters, starting from <code>Aa</code> for base-<code>11</code> integer, to <code>Zz</code> for base-<code>36</code> integer. The case of the characters is ignored.</p>
<p>Additional numeric formats may be accepted by the currently installed C <a href="../../locale/setlocale" title="c/locale/setlocale">locale</a>.</p>
<p>If the value of <code>base</code> is <code>0</code>, the numeric base is auto-detected: if the prefix is <code>0</code>, the base is octal, if the prefix is <code>0x</code> or <code>0X</code>, the base is hexadecimal, otherwise the base is decimal.</p>
<p>If the minus sign was part of the input sequence, the numeric value calculated from the sequence of digits is negated as if by <a href="../../language/operator_arithmetic#Unary_arithmetic" title="c/language/operator arithmetic">unary minus</a> in the result type, which applies unsigned integer wraparound rules.</p>
<p>The functions sets the pointer pointed to by <code>str_end</code> to point to the character past the last character interpreted. If <code>str_end</code> is a null pointer, it is ignored.</p>
<h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> str </td> <td> - </td> <td> pointer to the null-terminated byte string to be interpreted </td>
</tr> <tr class="t-par"> <td> str_end </td> <td> - </td> <td> pointer to a pointer to character, might be set to a position past the last character interpreted </td>
</tr> <tr class="t-par"> <td> base </td> <td> - </td> <td> <i>base</i> of the interpreted integer value </td>
</tr>
</table> <h3 id="Return_value"> Return value</h3> <p>Integer value corresponding to the contents of <code>str</code> on success. If the converted value falls out of range of corresponding return type, range error occurs (<code><a href="../../error/errno" title="c/error/errno">errno</a></code> is set to <code>ERANGE</code>) and <code><a href="../../types/limits" title="c/types/limits">ULONG_MAX</a></code> or <code><a href="../../types/limits" title="c/types/limits">ULLONG_MAX</a></code> is returned. If no conversion can be performed, <code>0</code> is returned.</p>
<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
const char *p = "10 200000000000000000000000000000 30 -40 - 42";
printf("Parsing '%s':\n", p);
char *end = NULL;
for (unsigned long i = strtoul(p, &end, 10);
p != end;
i = strtoul(p, &end, 10))
{
printf("'%.*s' -> ", (int)(end - p), p);
p = end;
if (errno == ERANGE)
{
errno = 0;
printf("range error, got ");
}
printf("%lu\n", i);
}
printf("After the loop p points to '%s'\n", p);
}</pre></div> <p>Output:</p>
<div class="text source-text"><pre data-language="c">Parsing '10 200000000000000000000000000000 30 -40 - 42':
'10' -> 10
' 200000000000000000000000000000' -> range error, got 18446744073709551615
' 30' -> 30
' -40' -> 18446744073709551576
After the loop p points to ' - 42'</pre></div> </div> <h3 id="References"> References</h3> <ul>
<li> C23 standard (ISO/IEC 9899:2023): </li>
<ul><li> 7.24.1.7 The strtol, strtoll, strtoul, and strtoull functions (p: TBD) </li></ul>
<li> C17 standard (ISO/IEC 9899:2018): </li>
<ul><li> 7.22.1.4 The strtol, strtoll, strtoul, and strtoull functions (p: 251-252) </li></ul>
<li> C11 standard (ISO/IEC 9899:2011): </li>
<ul><li> 7.22.1.4 The strtol, strtoll, strtoul, and strtoull functions (p: 344-345) </li></ul>
<li> C99 standard (ISO/IEC 9899:1999): </li>
<ul><li> 7.20.1.4 The strtol, strtoll, strtoul, and strtoull functions (p: 310-311) </li></ul>
<li> C89/C90 standard (ISO/IEC 9899:1990): </li>
<ul><li> 4.10.1.6 The strtoul function </li></ul>
</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="../wide/wcstoul" title="c/string/wide/wcstoul"> <span class="t-lines"><span>wcstoul</span><span>wcstoull</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c95">(C95)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> converts a wide string to an unsigned integer value <br> <span class="t-mark">(function)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="atoi" title="c/string/byte/atoi"> <span class="t-lines"><span>atoi</span><span>atol</span><span>atoll</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> converts a byte string to an integer value <br> <span class="t-mark">(function)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="strtol" title="c/string/byte/strtol"> <span class="t-lines"><span>strtol</span><span>strtoll</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> converts a byte string to an integer value <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/strtoul" title="cpp/string/byte/strtoul">C++ documentation</a></span> for <code>strtoul</code> </td>
</tr> </table> <div class="_attribution">
<p class="_attribution-p">
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