232 lines
9.9 KiB
HTML
232 lines
9.9 KiB
HTML
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<title>strtoul</title>
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<basefont size="3"> <a name="strtoul"></a> <a name="tag_03_746"></a><!-- strtoul -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_746_01"></a>NAME</h4>
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<blockquote>strtoul, strtoull - convert a string to an unsigned long</blockquote>
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<h4><a name="tag_03_746_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/stdlib.h.html">stdlib.h</a>><br>
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<br>
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unsigned long strtoul(const char *restrict</tt> <i>str</i><tt>,<br>
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char **restrict</tt> <i>endptr</i><tt>, int</tt> <i>base</i><tt>);<br>
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unsigned long long strtoull(const char *restrict</tt> <i>str</i><tt>,<br>
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char **restrict</tt> <i>endptr</i><tt>, int</tt> <i>base</i><tt>);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_746_03"></a>DESCRIPTION</h4>
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<blockquote>
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<div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"
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border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
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requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to
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the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div>
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<p>These functions shall convert the initial portion of the string pointed to by <i>str</i> to a type <b>unsigned long</b> and
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<b>unsigned long long</b> representation, respectively. First, they decompose the input string into three parts:</p>
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<ol>
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<li>
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<p>An initial, possibly empty, sequence of white-space characters (as specified by <a href=
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"../functions/isspace.html"><i>isspace</i>()</a>)</p>
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</li>
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<li>
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<p>A subject sequence interpreted as an integer represented in some radix determined by the value of <i>base</i></p>
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</li>
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<li>
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<p>A final string of one or more unrecognized characters, including the terminating null byte of the input string</p>
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</li>
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</ol>
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<p>Then they shall attempt to convert the subject sequence to an unsigned integer, and return the result.</p>
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<p>If the value of <i>base</i> is 0, the expected form of the subject sequence is that of a decimal constant, octal constant, or
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hexadecimal constant, any of which may be preceded by a <tt>'+'</tt> or <tt>'-'</tt> sign. A decimal constant begins with a
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non-zero digit, and consists of a sequence of decimal digits. An octal constant consists of the prefix <tt>'0'</tt> optionally
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followed by a sequence of the digits <tt>'0'</tt> to <tt>'7'</tt> only. A hexadecimal constant consists of the prefix 0x or 0X
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followed by a sequence of the decimal digits and letters <tt>'a'</tt> (or <tt>'A'</tt> ) to <tt>'f'</tt> (or <tt>'F'</tt> ) with
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values 10 to 15 respectively.</p>
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<p>If the value of <i>base</i> is between 2 and 36, the expected form of the subject sequence is a sequence of letters and digits
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representing an integer with the radix specified by <i>base</i>, optionally preceded by a <tt>'+'</tt> or <tt>'-'</tt> sign. The
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letters from <tt>'a'</tt> (or <tt>'A'</tt> ) to <tt>'z'</tt> (or <tt>'Z'</tt> ) inclusive are ascribed the values 10 to 35; only
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letters whose ascribed values are less than that of <i>base</i> are permitted. If the value of <i>base</i> is 16, the characters 0x
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or 0X may optionally precede the sequence of letters and digits, following the sign if present.</p>
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<p>The subject sequence is defined as the longest initial subsequence of the input string, starting with the first non-white-space
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character that is of the expected form. The subject sequence shall contain no characters if the input string is empty or consists
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entirely of white-space characters, or if the first non-white-space character is other than a sign or a permissible letter or
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digit.</p>
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<p>If the subject sequence has the expected form and the value of <i>base</i> is 0, the sequence of characters starting with the
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first digit shall be interpreted as an integer constant. If the subject sequence has the expected form and the value of <i>base</i>
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is between 2 and 36, it shall be used as the base for conversion, ascribing to each letter its value as given above. If the subject
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sequence begins with a minus sign, the value resulting from the conversion shall be negated. A pointer to the final string shall be
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stored in the object pointed to by <i>endptr</i>, provided that <i>endptr</i> is not a null pointer.</p>
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<p>In other than the C <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> or POSIX <img src="../images/opt-end.gif" alt="[Option End]" border="0"> locales, other
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implementation-defined subject sequences may be accepted.</p>
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<p>If the subject sequence is empty or does not have the expected form, no conversion shall be performed; the value of <i>str</i>
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shall be stored in the object pointed to by <i>endptr</i>, provided that <i>endptr</i> is not a null pointer.</p>
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<p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> The
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<i>strtoul</i>() function shall not change the setting of <i>errno</i> if successful.</p>
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<p>Since 0, {ULONG_MAX}, and {ULLONG_MAX} are returned on error and are also valid returns on success, an application wishing to
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check for error situations should set <i>errno</i> to 0, then call <i>strtoul</i>() or <i>strtoull</i>(), then check <i>errno</i>.
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<img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_03_746_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, these functions shall return the converted value, if any. If no conversion could be performed, 0
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shall be returned <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"
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border="0"> and <i>errno</i> may be set to [EINVAL]. <img src="../images/opt-end.gif" alt="[Option End]" border="0"> If the
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correct value is outside the range of representable values, {ULONG_MAX} or {ULLONG_MAX} shall be returned and <i>errno</i> set to
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[ERANGE].</p>
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</blockquote>
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<h4><a name="tag_03_746_05"></a>ERRORS</h4>
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<blockquote>
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<p>These functions shall fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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The value of <i>base</i> is not supported. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
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<dt>[ERANGE]</dt>
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<dd>The value to be returned is not representable.</dd>
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</dl>
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<p>These functions may fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> No
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conversion could be performed. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_746_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_746_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_746_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_746_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_746_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="isalpha.html"><i>isalpha</i>()</a> , <a href="scanf.html"><i>scanf</i>()</a> , <a href=
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"strtod.html"><i>strtod</i>()</a> , <a href="strtol.html"><i>strtol</i>()</a> , the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/stdlib.h.html"><i><stdlib.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_746_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 4. Derived from the ANSI C standard.</p>
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</blockquote>
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<h4><a name="tag_03_746_12"></a>Issue 5</h4>
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<blockquote>
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<p>The DESCRIPTION is updated to indicate that <i>errno</i> is not changed if the function is successful.</p>
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</blockquote>
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<h4><a name="tag_03_746_13"></a>Issue 6</h4>
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<blockquote>
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<p>Extensions beyond the ISO C standard are marked.</p>
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<p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p>
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<ul>
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<li>
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<p>The [EINVAL] error condition is added for when the value of <i>base</i> is not supported.</p>
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<p>In the RETURN VALUE and ERRORS sections, the [EINVAL] optional error condition is added if no conversion could be performed.</p>
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</li>
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</ul>
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<p>The following changes are made for alignment with the ISO/IEC 9899:1999 standard:</p>
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<ul>
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<li>
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<p>The <i>strtoul</i>() prototype is updated.</p>
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</li>
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<li>
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<p>The <i>strtoull</i>() function is added.</p>
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</li>
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</ul>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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UNIX ® is a registered Trademark of The Open Group.<br>
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POSIX ® is a registered Trademark of The IEEE.<br>
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[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href=
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"../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>
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