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<h1 id="firstHeading" class="firstHeading">strtol, strtoll</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">long strtol( 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">long strtol( 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">long long strtoll( 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 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>) integer number representation and converts them to an integer value. The valid 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.</p>
<p>The functions set the pointer pointed to by <code>str_end</code> to point to the character past the last numeric character interpreted. If <code>str_end</code> is a null pointer, it is ignored.</p>
<p>If the <code>str</code> is empty or does not have the expected form, no conversion is performed, and (if <code>str_end</code> is not a null pointer) the value of <code>str</code> is stored in the object pointed to by <code>str_end</code>.</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. </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> <ul>
<li> If successful, an integer value corresponding to the contents of <code>str</code> is returned. </li>
<li> If the converted value falls out of range of corresponding return type, a range error occurs (setting <code><a href="../../error/errno" title="c/error/errno">errno</a></code> to <code><a href="../../error/errno_macros" title="c/error/errno macros">ERANGE</a></code>) and <code><a href="../../types/limits" title="c/types/limits">LONG_MAX</a></code>, <code><a href="../../types/limits" title="c/types/limits">LONG_MIN</a></code>, <code><a href="../../types/limits" title="c/types/limits">LLONG_MAX</a></code> or <code><a href="../../types/limits" title="c/types/limits">LLONG_MIN</a></code> is returned. </li>
<li> If no conversion can be performed, <code>0</code> is returned. </li>
</ul> <h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include <errno.h>
#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
// parsing with error handling
const char *p = "10 200000000000000000000000000000 30 -40 junk";
printf("Parsing '%s':\n", p);
for (;;)
{
// errno can be set to any non-zero value by a library function call
// regardless of whether there was an error, so it needs to be cleared
// in order to check the error set by strtol
errno = 0;
char *end;
const long i = strtol(p, &end, 10);
if (p == end)
break;
const bool range_error = errno == ERANGE;
printf("Extracted '%.*s', strtol returned %ld.", (int)(end-p), p, i);
p = end;
if (range_error)
printf("\n --> Range error occurred.");
putchar('\n');
}
printf("Unextracted leftover: '%s'\n\n", p);
// parsing without error handling
printf("\"1010\" in binary --> %ld\n", strtol("1010", NULL, 2));
printf("\"12\" in octal --> %ld\n", strtol("12", NULL, 8));
printf("\"A\" in hex --> %ld\n", strtol("A", NULL, 16));
printf("\"junk\" in base-36 --> %ld\n", strtol("junk", NULL, 36));
printf("\"012\" in auto-detected base --> %ld\n", strtol("012", NULL, 0));
printf("\"0xA\" in auto-detected base --> %ld\n", strtol("0xA", NULL, 0));
printf("\"junk\" in auto-detected base --> %ld\n", strtol("junk", NULL, 0));
}</pre></div> <p>Possible output:</p>
<div class="text source-text"><pre data-language="c">Parsing '10 200000000000000000000000000000 30 -40 junk':
Extracted '10', strtol returned 10.
Extracted ' 200000000000000000000000000000', strtol returned 9223372036854775807.
--> Range error occurred.
Extracted ' 30', strtol returned 30.
Extracted ' -40', strtol returned -40.
Unextracted leftover: ' junk'
"1010" in binary --> 10
"12" in octal --> 10
"A" in hex --> 10
"junk" in base-36 --> 926192
"012" in auto-detected base --> 10
"0xA" in auto-detected base --> 10
"junk" in auto-detected base --> 0</pre></div> </div> <h3 id="References"> References</h3> <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> 4.10.1.5 The strtol function </li></ul>
</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <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="strtoul" title="c/string/byte/strtoul"> <span class="t-lines"><span>strtoul</span><span> strtoull</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 unsigned integer value <br> <span class="t-mark">(function)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="../wide/wcstol" title="c/string/wide/wcstol"> <span class="t-lines"><span>wcstol</span><span>wcstoll</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 integer value <br> <span class="t-mark">(function)</span> </td>
</tr> <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 colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/string/byte/strtol" title="cpp/string/byte/strtol">C++ documentation</a></span> for <code>strtol, strtoll</code> </td>
</tr> </table> <div class="_attribution">
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