fwprintf.html

unix 下的C开发手册,还用详细的例程。

<p>
The conversion wide-characters and their meanings are:
<dl compact>

<dt>d,&nbsp;i<dd>The <b>int</b> argument is converted to a signed decimal
in the style <b>[</b>-<b>]</b><i>dddd</i>.
The precision specifies the minimum number of digits to appear;
if the value being converted can be represented in fewer digits,
it will be expanded with leading zeros. The default precision is
1. The result of converting 0 with an explicit precision
of 0 is no wide-characters.

<dt>o<dd>The <b>unsigned int</b> argument is converted to unsigned octal format
in the style <i>dddd</i>.
The precision specifies the minimum number of digits to appear; if
the value being converted can be represented in fewer digits, it will be
expanded with leading zeros. The default precision is 1. The result of
converting 0 with an explicit precision of 0 is no wide-characters.

<dt>u<dd>The <b>unsigned int</b> argument is converted to unsigned decimal format
in the style
<i>dddd</i>.
The precision specifies the minimum number of digits to appear; if
the value being converted can be represented in fewer digits, it will be
expanded with leading zeros. The default precision is 1. The result of
converting 0 with an explicit precision of 0 is no wide-characters.


<dt>x<dd>The <b>unsigned int</b> argument is converted to unsigned hexadecimal format
in the style
<i>dddd</i>;
the letters abcdef are used.
The precision specifies the minimum number of digits to appear; if
the value being converted can be represented in fewer digits, it will be
expanded with leading zeros. The default precision is 1. The result of
converting 0 with an explicit precision of 0 is no wide-characters.


<dt>X<dd>Behaves the same as the x conversion wide-character except that
letters ABCDEF are used instead of abcdef.

<dt>f<dd>The
<b>double</b>
argument is converted to decimal notation in the style
<b>[</b>-<b>]</b><i>ddd.ddd</i>, where the number of digits after the
radix character is equal to the precision specification.
If the precision is missing, it is taken as 6; if the precision is
explicitly 0 and no # flag is present, no radix character appears.
If a radix character appears, at least one digit appears
before it.
The value is rounded to the appropriate number of digits.

The
<i>fwprintf()</i>
family of functions may make available wide-character string 
representations for infinity and NaN.

<dt>e, E<dd>The
<b>double</b>
argument is converted in the style
<b>[</b>-<b>]</b><i>d.ddd</i>e<i>&plusmn;dd</i>,
where there is one digit before the radix character
(which is non-zero if the argument is non-zero) and the number of
digits after it is equal to the precision; if the precision is
missing, it is taken as 6; if the precision is 0 and no # flag
is present, no radix character appears.
The value is rounded to the appropriate number of digits.
The E conversion wide-character will produce a number with E 
instead of e introducing the exponent.
The exponent always contains at least two digits.
If the value is 0, the exponent is 0.

The
<i>fwprintf()</i>
family of functions may make available wide-character string 
representations for infinity and NaN.


<dt>g, G<dd>The
<b>double</b>
argument is converted in the style f or e (or in the style E
in the case of a G conversion wide-character),
with the precision specifying the number of significant digits.
If an explicit precision is 0, it is taken as 1.
The style used depends on the value converted; style e (or E)
will be used only if the exponent resulting from such a
conversion is less than -4 or greater than or equal to the
precision.
Trailing zeros are removed from the fractional portion of the
result; a radix character appears only if it is followed
by a digit.

The
<i>fwprintf()</i>
family of functions may make available wide-character string 
representations for infinity and NaN.


<dt>c<dd>If no l (ell) qualifier is present, the
<b>int</b>
argument is converted to a wide-character as if by calling the
<i><a href="btowc.html">btowc()</a></i>
function and the resulting wide-character is written.  Otherwise the
<b>wint_t</b>
argument is converted to
<b>wchar_t</b>,
and written.


<dt>s<dd>If no l (ell) qualifier is present, the argument must be a pointer to a
character array containing a character sequence beginning in the
initial shift state.
Characters from the array are converted as if by repeated calls
to the
<i><a href="mbrtowc.html">mbrtowc()</a></i>
function, with the conversion state described by an
<b>mbstate_t</b>
object initialised to zero before the first character is
converted, and written up to (but not including) the terminating 
null wide-character.  
If the precision is specified, no
more than that many wide-characters are written.
If the precision is not specified or is greater than the size of
the array, the array must contain a null wide-character.

If an l (ell) qualifier is present, the argument must be a pointer to 
an array of type
<b>wchar_t</b>.
Wide characters from the array are written up to (but not including) a
terminating null wide-character.
If no precision is specified or is greater than the size of the array,
the array must contain a null wide-character.   If a precision is
specified, no more than that many wide-characters are written.

<dt>p<dd>The argument must be a pointer to
<b>void</b>.
The value of the pointer is converted to a sequence of printable
wide-characters, in an implementation-dependent manner.

<dt>n<dd>The argument must be a pointer to an integer into which is written
the number of wide-characters written to the output so far by this 
call to one of the
<i>fwprintf()</i>
functions.
No argument is converted.


<dt>C<dd>Same as <b>lc</b>.

<dt>S<dd>Same as <b>ls</b>.

<dt>%<dd>Output a % wide-character; no argument is converted.
The entire conversion specification must be %%.

</dl>
<p>
If a conversion specification does not match one of the
above forms, the behaviour is undefined.
<p>
In no case does a non-existent or small field width
cause truncation of a field;
if the result of a conversion is wider than the field width,
the field is simply expanded to contain the conversion result.
Characters generated by
<i>fwprintf()</i>
and
<i><a href="wprintf.html">wprintf()</a></i>
are printed as if
<i><a href="fputwc.html">fputwc()</a></i>
had been called.
<p>
The
<i>st_ctime</i>
and
<i>st_mtime</i>
fields of the file will be marked for update between the call to
a successful execution of
<i>fwprintf()</i>
or
<i><a href="wprintf.html">wprintf()</a></i>
and the next successful completion of a call to
<i><a href="fflush.html">fflush()</a></i>
or
<i><a href="fclose.html">fclose()</a></i>
on the same stream or a call to
<i><a href="exit.html">exit()</a></i>
or
<i><a href="abort.html">abort()</a></i>.
</blockquote><h4><a name = "tag_000_005_407">&nbsp;</a>RETURN VALUE</h4><blockquote>
Upon successful completion, these functions
return the number of wide-characters transmitted
excluding the terminating null wide-character in the case of
<i><a href="swprintf.html">swprintf()</a></i>
or
a negative value if an output error was encountered.
If n or more wide characters were requested to be written
<i><a href="swprintf.html">swprintf()</a></i>
returns a negative value.
</blockquote><h4><a name = "tag_000_005_408">&nbsp;</a>ERRORS</h4><blockquote>
For the conditions under which
<i>fwprintf()</i>
and
<i><a href="wprintf.html">wprintf()</a></i>
will fail and may fail, refer to
<i><a href="fputwc.html">fputwc()</a></i>.
<p>
In addition, all forms of
<i>fwprintf()</i>
may fail if:
<dl compact>

<dt>[EILSEQ]<dd>
A wide-character code that does not correspond to a valid character has been
detected.

<dt>[EINVAL]<dd>
There are insufficient arguments.

</dl>
<p>
In addition,
<i><a href="wprintf.html">wprintf()</a></i>
and
<i>fwprintf()</i>
may fail if:
<dl compact>

<dt>[ENOMEM]<dd>
Insufficient storage space is available.

</dl>
</blockquote><h4><a name = "tag_000_005_409">&nbsp;</a>EXAMPLES</h4><blockquote>
To print the language-independent date and time format, the
following statement could be used:
<pre>
<code>
wprintf (format, weekday, month, day, hour, min);
</code>
</pre>
For American usage,
<i>format</i>
could be a pointer to the wide-character string:
<pre>
<code>
L"%s, %s %d, %d:%.2d\n"
</code>
</pre>
producing the message:
<pre>
<code>
Sunday, July 3, 10:02
</code>
</pre>
whereas for German usage,
<i>format</i>
could be a pointer to the wide-character string:
<pre>
<code>
L"%1$s, %3$d. %2$s, %4$d:%5$.2d\n"
</code>
</pre>
producing the message:
<pre>
<code>
Sonntag, 3. Juli, 10:02
</code>
</pre>
</blockquote><h4><a name = "tag_000_005_410">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_005_411">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_005_412">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="btowc.html">btowc()</a></i>,
<i><a href="fputwc.html">fputwc()</a></i>,
<i><a href="fwscanf.html">fwscanf()</a></i>,
<i><a href="setlocale.html">setlocale()</a></i>,
<i><a href="mbrtowc.html">mbrtowc()</a></i>,
<i><a href="stdio.h.html">&lt;stdio.h&gt;</a></i>,
<i><a href="wchar.h.html">&lt;wchar.h&gt;</a></i>,
the <b>XBD</b> specification, <a href="../xbd/locale.html"><b>Locale</b>&nbsp;</a>.
</blockquote><hr size=2 noshade>
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