wscanf.html

posix标准英文,html格式

automatically. 

<p>If an <tt>l</tt> (ell) qualifier is present, the application shall ensure that the corresponding argument is a pointer to an
array of <b>wchar_t</b> large enough to accept the sequence and the terminating null wide character, which shall be added
automatically.</p>

<p>The conversion specification includes all subsequent wide characters in the <i>format</i> string up to and including the
matching right square bracket ( <tt>']'</tt> ). The wide characters between the square brackets (the <i>scanlist</i>) comprise the
scanset, unless the wide character after the left square bracket is a circumflex ( <tt>'^'</tt> ), in which case the scanset
contains all wide characters that do not appear in the scanlist between the circumflex and the right square bracket. If the
conversion specification begins with <tt>"[]"</tt> or <tt>"[^]"</tt>, the right square bracket is included in the scanlist and the
next right square bracket is the matching right square bracket that ends the conversion specification; otherwise, the first right
square bracket is the one that ends the conversion specification. If a <tt>'-'</tt> is in the scanlist and is not the first wide
character, nor the second where the first wide character is a <tt>'^'</tt>, nor the last wide character, the behavior is
implementation-defined.</p>
</dd>

<dt><tt>c</tt></dt>

<dd>Matches a sequence of wide characters of exactly the number specified by the field width (1 if no field width is present in the
conversion specification). 

<p>If no <tt>l</tt> (ell) length modifier is present, characters from the input field shall be converted as if by repeated calls to
the <a href="../functions/wcrtomb.html"><i>wcrtomb</i>()</a> function, with the conversion state described by an <b>mbstate_t</b>
object initialized to zero before the first wide character is converted. The corresponding argument shall be a pointer to the
initial element of a character array large enough to accept the sequence. No null character is added.</p>

<p>If an <tt>l</tt> (ell) length modifier is present, the corresponding argument shall be a pointer to the initial element of an
array of <b>wchar_t</b> large enough to accept the sequence. No null wide character is added.</p>

<p>Otherwise, the application shall ensure that the corresponding argument is a pointer to an array of <b>wchar_t</b> large enough
to accept the sequence. No null wide character is added.</p>
</dd>

<dt><tt>p</tt></dt>

<dd>Matches an implementation-defined set of sequences, which shall be the same as the set of sequences that is produced by the
<tt>%p</tt> conversion specification of the corresponding <a href="../functions/fwprintf.html"><i>fwprintf</i>()</a> functions. The
application shall ensure that the corresponding argument is a pointer to a pointer to <b>void</b>. The interpretation of the input
item is implementation-defined. If the input item is a value converted earlier during the same program execution, the pointer that
results shall compare equal to that value; otherwise, the behavior of the <tt>%p</tt> conversion is undefined.</dd>

<dt><tt>n</tt></dt>

<dd>No input is consumed. The application shall ensure that the corresponding argument is a pointer to the integer into which is to
be written the number of wide characters read from the input so far by this call to the <i>fwscanf</i>() functions. Execution of a
<tt>%n</tt> conversion specification shall not increment the assignment count returned at the completion of execution of the
function. No argument shall be converted, but one shall be consumed. If the conversion specification includes an
assignment-suppressing wide character or a field width, the behavior is undefined.</dd>

<dt><tt>C</tt></dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
Equivalent to <tt>lc</tt>. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt><tt>S</tt></dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
Equivalent to <tt>ls</tt>. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt><tt>%</tt></dt>

<dd>Matches a single <tt>'%'</tt> wide character; no conversion or assignment shall occur. The complete conversion specification
shall be <tt>%%</tt>.</dd>
</dl>

<p>If a conversion specification is invalid, the behavior is undefined.</p>

<p>The conversion specifiers <tt>A</tt>, <tt>E</tt>, <tt>F</tt>, <tt>G</tt>, and <tt>X</tt> are also valid and shall be
equivalent to, respectively, <tt>a</tt>, <tt>e</tt>, <tt>f</tt>, <tt>g</tt>, and <tt>x</tt>.</p>

<p>If end-of-file is encountered during input, conversion is terminated. If end-of-file occurs before any wide characters matching
the current conversion specification (except for <tt>%n</tt> ) have been read (other than leading white-space, where permitted),
execution of the current conversion specification shall terminate with an input failure. Otherwise, unless execution of the current
conversion specification is terminated with a matching failure, execution of the following conversion specification (if any) shall
be terminated with an input failure.</p>

<p>Reaching the end of the string in <i>swscanf</i>() shall be equivalent to encountering end-of-file for <i>fwscanf</i>().</p>

<p>If conversion terminates on a conflicting input, the offending input shall be left unread in the input. Any trailing white space
(including &lt;newline&gt;) shall be left unread unless matched by a conversion specification. The success of literal matches and
suppressed assignments is only directly determinable via the <tt>%n</tt> conversion specification.</p>

<p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> The
<i>fwscanf</i>() and <i>wscanf</i>() functions may mark the <i>st_atime</i> field of the file associated with <i>stream</i> for
update. The <i>st_atime</i> field shall be marked for update by the first successful execution of <a href=
"../functions/fgetc.html"><i>fgetc</i>()</a>, <a href="../functions/fgetwc.html"><i>fgetwc</i>()</a>, <a href=
"../functions/fgets.html"><i>fgets</i>()</a>, <a href="../functions/fgetws.html"><i>fgetws</i>()</a>, <a href=
"../functions/fread.html"><i>fread</i>()</a>, <a href="../functions/getc.html"><i>getc</i>()</a>, <a href=
"../functions/getwc.html"><i>getwc</i>()</a>, <a href="../functions/getchar.html"><i>getchar</i>()</a>, <a href=
"../functions/getwchar.html"><i>getwchar</i>()</a>, <a href="../functions/gets.html"><i>gets</i>()</a>, <a href=
"../functions/fscanf.html"><i>fscanf</i>()</a>, or <i>fwscanf</i>() using <i>stream</i> that returns data not supplied by a prior
call to <a href="../functions/ungetc.html"><i>ungetc</i>()</a>. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
</blockquote>

<h4><a name="tag_03_206_04"></a>RETURN VALUE</h4>

<blockquote>
<p>Upon successful completion, these functions shall return the number of successfully matched and assigned input items; this
number can be zero in the event of an early matching failure. If the input ends before the first matching failure or conversion,
EOF shall be returned. If a read error occurs, the error indicator for the stream is set, EOF shall be returned, <sup>[<a href=
"javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> &nbsp;and
<i>errno</i> shall be set to indicate the error. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
</blockquote>

<h4><a name="tag_03_206_05"></a>ERRORS</h4>

<blockquote>
<p>For the conditions under which the <i>fwscanf</i>() functions shall fail and may fail, refer to <a href=
"fgetwc.html"><i>fgetwc</i>()</a>.</p>

<p>In addition, <i>fwscanf</i>() may fail if:</p>

<dl compact>
<dt>[EILSEQ]</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
Input byte sequence does not form a valid character. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>[EINVAL]</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
There are insufficient arguments. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
</dl>
</blockquote>

<hr>
<div class="box"><em>The following sections are informative.</em></div>

<h4><a name="tag_03_206_06"></a>EXAMPLES</h4>

<blockquote>
<p>The call:</p>

<pre>
<tt>int i, n; float x; char name[50];
n = wscanf(L"%d%f%s", &amp;i, &amp;x, name);
</tt>
</pre>

<p>with the input line:</p>

<pre>
<tt>25 54.32E-1 Hamster
</tt>
</pre>

<p>assigns to <i>n</i> the value 3, to <i>i</i> the value 25, to <i>x</i> the value 5.432, and <i>name</i> contains the string
<tt>"Hamster"</tt>.</p>

<p>The call:</p>

<pre>
<tt>int i; float x; char name[50];
(void) wscanf(L"%2d%f%*d %[0123456789]", &amp;i, &amp;x, name);
</tt>
</pre>

<p>with input:</p>

<pre>
<tt>56789 0123 56a72
</tt>
</pre>

<p>assigns 56 to <i>i</i>, 789.0 to <i>x</i>, skips 0123, and places the string <tt>"56\0"</tt> in <i>name</i>. The next call to <a
href="../functions/getchar.html"><i>getchar</i>()</a> shall return the character <tt>'a'</tt>.</p>
</blockquote>

<h4><a name="tag_03_206_07"></a>APPLICATION USAGE</h4>

<blockquote>
<p>In format strings containing the <tt>'%'</tt> form of conversion specifications, each argument in the argument list is used
exactly once.</p>
</blockquote>

<h4><a name="tag_03_206_08"></a>RATIONALE</h4>

<blockquote>
<p>None.</p>
</blockquote>

<h4><a name="tag_03_206_09"></a>FUTURE DIRECTIONS</h4>

<blockquote>
<p>None.</p>
</blockquote>

<h4><a name="tag_03_206_10"></a>SEE ALSO</h4>

<blockquote>
<p><a href="getwc.html"><i>getwc</i>()</a>, <a href="fwprintf.html"><i>fwprintf</i>()</a>, <a href=
"setlocale.html"><i>setlocale</i>()</a>, <a href="wcstod.html"><i>wcstod</i>()</a>, <a href="wcstol.html"><i>wcstol</i>()</a>,
<a href="wcstoul.html"><i>wcstoul</i>()</a>, <a href="wcrtomb.html"><i>wcrtomb</i>()</a>, the Base Definitions volume of
IEEE&nbsp;Std&nbsp;1003.1-2001, <a href="../basedefs/xbd_chap07.html">Chapter 7, Locale</a>, <a href=
"../basedefs/langinfo.h.html"><i>&lt;langinfo.h&gt;</i></a>, <a href="../basedefs/stdio.h.html"><i>&lt;stdio.h&gt;</i></a>, <a
href="../basedefs/wchar.h.html"><i>&lt;wchar.h&gt;</i></a></p>
</blockquote>

<h4><a name="tag_03_206_11"></a>CHANGE HISTORY</h4>

<blockquote>
<p>First released in Issue 5. Included for alignment with ISO/IEC&nbsp;9899:1990/Amendment 1:1995 (E).</p>
</blockquote>

<h4><a name="tag_03_206_12"></a>Issue 6</h4>

<blockquote>
<p>The DESCRIPTION is updated to avoid use of the term &quot;must&quot; for application requirements.</p>

<p>The following changes are made for alignment with the ISO/IEC&nbsp;9899:1999 standard:</p>

<ul>
<li>
<p>The prototypes for <i>fwscanf</i>() and <i>swscanf</i>() are updated.</p>
</li>

<li>
<p>The DESCRIPTION is updated.</p>
</li>

<li>
<p>The <tt>hh</tt>, <tt>ll</tt>, <tt>j</tt>, <tt>t</tt>, and <tt>z</tt> length modifiers are added.</p>
</li>

<li>
<p>The <tt>a</tt>, <tt>A</tt>, and <tt>F</tt> conversion characters are added.</p>
</li>
</ul>

<p>The DESCRIPTION is updated to use the terms &quot;conversion specifier&quot; and &quot;conversion specification&quot; consistently.</p>
</blockquote>

<div class="box"><em>End of informative text.</em></div>

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