fiolib.html

Vxworks API操作系统和驱动程序设计API。压缩的HTML文件

<p>
</blockquote><h4>RETURNS</h4><blockquote><p>
<p>
The number of bytes read, or ERROR if there is an error during the read
operation.
<p>
</blockquote><h4>SEE ALSO</h4><blockquote><p>
<b><a href="./fioLib.html#top">fioLib</a></b>, <b><a href="./ioLib.html#read">read</a>(&nbsp;)</b>

<hr>
<a name="fioRdString"></a>
<p align=right>
<a href="rtnIndex.htm"><i>OS Libraries :  Routines</i></a></p>

</blockquote><h1>fioRdString(&nbsp;)</h1> <blockquote></a></blockquote><h4>NAME</h4><blockquote>  
<p><strong>fioRdString(&nbsp;)</strong> - read a string from a file</p>

</blockquote><h4>SYNOPSIS</h4><blockquote><p>
<pre>int fioRdString
    (
    int  fd,                  /* fd of device to read */
    char string[],            /* buffer to receive input */
    int  maxbytes             /* max no. of chars to read */
    )
</pre>

</blockquote><h4>DESCRIPTION</h4><blockquote><p>
This routine puts a line of input into <i>string</i>.  The specified input
file descriptor is read until <i>maxbytes</i>, an EOF, an EOS, or a newline
character is reached.  A newline character or EOF is replaced with EOS,
unless <i>maxbytes</i> characters have been read.
<p>
</blockquote><h4>RETURNS</h4><blockquote><p>
<p>
The length of the string read, including the terminating EOS;
or EOF if a read error occurred or end-of-file occurred without
reading any other character.
</blockquote><h4>SEE ALSO</h4><blockquote><p>
<b><a href="./fioLib.html#top">fioLib</a></b>

<hr>
<a name="sscanf"></a>
<p align=right>
<a href="rtnIndex.htm"><i>OS Libraries :  Routines</i></a></p>

</blockquote><h1>sscanf(&nbsp;)</h1> <blockquote></a></blockquote><h4>NAME</h4><blockquote>  
<p><strong>sscanf(&nbsp;)</strong> - read and convert characters from an ASCII string (ANSI)</p>

</blockquote><h4>SYNOPSIS</h4><blockquote><p>
<pre>int sscanf
    (
    const char * str,         /* string to scan */
    const char * fmt,         /* format string */
                 ...          /* optional arguments to format string */
    )
</pre>

</blockquote><h4>DESCRIPTION</h4><blockquote><p>
This routine reads characters from the string <i>str</i>, interprets them
according to format specifications in the string <i>fmt</i>, which specifies
the admissible input sequences and how they are to be converted for
assignment, using subsequent arguments as pointers to the objects to
receive the converted input.
<p>
If there are insufficient arguments for the format, the behavior is
undefined.  If the format is exhausted while arguments remain, the excess
arguments are evaluated but are otherwise ignored.
<p>
The format is a multibyte character sequence, beginning and ending in
its initial shift state.  The format is composed of zero or more directives:
one or more white-space characters; an ordinary multibyte character (neither
<b>%</b> nor a white-space character); or a conversion specification.  Each
conversion specification is introduced by the <b>%</b> character.  After the <b>%</b>,
the following appear in sequence:
<p>
<ul>

<li>An optional assignment-suppressing character <b>*</b>.</li>
<li>An optional non-zero decimal integer that specifies the maximum field </li>
width.
<li>An optional <b>h</b>, <b>l</b> (ell) or <b>ll</b> (ell-ell) indicating the size of the </li>
receiving object.  The conversion specifiers <b>d</b>, <b>i</b>, and <b>n</b> should 
be preceded by <b>h</b> if the corresponding argument is a pointer to <b>short 
int</b> rather than a pointer to <b>int</b>, or by <b>l</b> if it is a pointer to 
<b>long int</b>, or by <b>ll</b> if it is a pointer to <b>long long int</b>.  Similarly, 
the conversion specifiers <b>o</b>, <b>u</b>, and <b>x</b> shall be preceded by <b>h</b> if 
the corresponding argument is a pointer to <b>unsigned short int</b> rather 
than a pointer to <b>unsigned int</b>, or by <b>l</b> if it is a pointer to 
<b>unsigned long int</b>, or by <b>ll</b> if it is a pointer to <b>unsigned long 
long int</b>.  Finally, the conversion specifiers <b>e</b>, <b>f</b>, and <b>g</b> shall 
be preceded by <b>l</b> if the corresponding argument is a pointer to 
<b>double</b> rather than a pointer to <b>float</b>.  If a <b>h</b>, <b>l</b> or <b>ll</b> 
appears with any other conversion specifier, the behavior is undefined.
<li>
</blockquote><h4>WARNING</h4><blockquote><p>
ANSI C also specifies an optional <b>L</b> in some of the same</li>
contexts as <b>l</b> above, corresponding to a <b>long double *</b> argument.
However, the current release of the VxWorks libraries does not support 
<b>long double</b> data; using the optional <b>L</b> gives unpredictable results.
<li>A character that specifies the type of conversion to be applied.  The</li>
valid conversion specifiers are described below.
</ul>

<p>

The <b><a href="./fioLib.html#sscanf">sscanf</a>(&nbsp;)</b> routine executes each directive of the format in turn.  If a 
directive fails, as detailed below, <b><a href="./fioLib.html#sscanf">sscanf</a>(&nbsp;)</b> returns.  Failures
are described as input failures (due to the unavailability of input
characters), or matching failures (due to inappropriate input).
<p>
A directive composed of white-space character(s) is executed by reading
input up to the first non-white-space character (which remains unread),
or until no more characters can be read.
<p>
A directive that is an ordinary multibyte character is executed by reading
the next characters of the stream.  If one of the characters differs from
one comprising the directive, the directive fails, and the differing and
subsequent characters remain unread.
<p>
A directive that is a conversion specification defines a set of matching
input sequences, as described below for each specifier.  A conversion
specification is executed in the following steps:
<p>
Input white-space characters (as specified by the <b><a href="./ansiCtype.html#isspace">isspace</a>(&nbsp;)</b> function) are 
skipped, unless the specification includes a <b>[</b>, <b>c</b>, or <b>n</b> specifier.
<p>
An input item is read from the stream, unless the specification includes
an <b>n</b> specifier.  An input item is defined as the longest matching
sequence of input characters, unless that exceeds a specified field width,
in which case it is the initial subsequence of that length in the
sequence.  The first character, if any, after the input item remains
unread.  If the length of the input item is zero, the execution of the
directive fails:  this condition is a matching failure, unless an error
prevented input from the stream, in which case it is an input failure.
<p>
Except in the case of a <b>%</b> specifier, the input item is converted to a
type appropriate to the conversion specifier.  If the input item is not a
matching sequence, the execution of the directive fails:  this condition
is a matching failure.  Unless assignment suppression was indicated by a
<b>*</b>, the result of the conversion is placed in the object pointed to by
the first argument following the <i>fmt</i> argument that has not already
received a conversion result.  If this object does not have an appropriate
type, or if the result of the conversion cannot be represented in the
space provided, the behavior is undefined.
<p>
The following conversion specifiers are valid:
<p>
<dl>
<dt>
<b>d</b>
<dd>
Matches an optionally signed decimal integer whose format is
the same as expected for the subject sequence of the <b><a href="./ansiStdlib.html#strtol">strtol</a>(&nbsp;)</b>
function with the value 10 for the <i>base</i> argument.  The 
corresponding argument should be a pointer to <b>int</b>.
<dt>
<b>i</b>
<dd>
Matches an optionally signed integer, whose format is the
same as expected for the subject sequence of the <b><a href="./ansiStdlib.html#strtol">strtol</a>(&nbsp;)</b>
function with the value 0 for the <i>base</i> argument.  The 
corresponding argument should be a pointer to <b>int</b>.
<dt>
<b>o</b>
<dd>
Matches an optionally signed octal integer, whose format is the
same as expected for the subject sequence of the <b><a href="./ansiStdlib.html#strtoul">strtoul</a>(&nbsp;)</b>
function with the value 8 for the <i>base</i> argument.  The
corresponding argument should be a pointer to <b>unsigned int</b>.
<dt>
<b>u</b>
<dd>
Matches an optionally signed decimal integer, whose format is 
the same as expected for the subject sequence of the <b><a href="./ansiStdlib.html#strtoul">strtoul</a>(&nbsp;)</b>
function with the value 10 for the <i>base</i> argument.  The
corresponding argument should be a pointer to <b>unsigned int</b>.
<dt>
<b>x</b>
<dd>
Matches an optionally signed hexadecimal integer, whose format is
the same as expected for the subject sequence of the <b><a href="./ansiStdlib.html#strtoul">strtoul</a>(&nbsp;)</b>
function with the value 16 for the <i>base</i> argument.  The
corresponding argument should be a pointer to <b>unsigned int</b>.
<dt>
<b>e</b>, <b>f</b>, <b>g</b>
<dd>
Match an optionally signed floating-point number, whose format
is the same as expected for the subject string of the <b><a href="./ansiStdlib.html#strtod">strtod</a>(&nbsp;)</b>
function.  The corresponding argument should be a pointer to <b>float</b>.
<dt>
<b>s</b>
<dd>
Matches a sequence of non-white-space characters.  The 
corresponding argument should be a pointer to the initial
character of an array large enough to accept the sequence
and a terminating null character, which will be added 
automatically.
<dt>
<b>[</b>
<dd>
Matches a non-empty sequence of characters from a set of 
expected characters (the <b>scanset</b>).  The corresponding argument
should be a pointer to the initial character of an array large
enough to accept the sequence and a terminating null character,
which is added automatically.  The conversion specifier
includes all subsequent character in the format string, up to
and including the matching right bracket (<b>]</b>).  The characters
between the brackets (the <b>scanlist</b>) comprise the scanset,
unless the character after the left bracket is a circumflex (<b>^</b>)
in which case the scanset contains all characters that do not
appear in the scanlist between the circumflex and the right
bracket.  If the conversion specifier begins with "[]" or "[^]", the
right bracket character is in the scanlist and the next 
right bracket character is the matching right bracket that ends
the specification; otherwise the first right bracket character
is the one that ends the specification.
<dt>
<b>c</b>
<dd>
Matches a sequence of characters of the number specified by the
field width (1 if no field width is present in the directive).
The corresponding argument should be a pointer to the initial 
character of an array large enough to accept the sequence.
No null character is added.
<dt>
<b>p</b>
<dd>
Matches an implementation-defined set of sequences, which should be
the same as the set of sequences that may be produced by the %p
conversion of the <b><a href="./ansiStdio.html#fprintf">fprintf</a>(&nbsp;)</b> function.  The corresponding argument
should be a pointer to a pointer to <b>void</b>.  VxWorks defines its
pointer input field to be consistent with pointers written by the
<b><a href="./ansiStdio.html#fprintf">fprintf</a>(&nbsp;)</b> function ("0x" hexadecimal notation).  If the input item is
a value converted earlier during the same program execution, the
pointer that results should compare equal to that value; otherwise
the behavior of the %p conversion is undefined.
<dt>
<b>n</b>
<dd>
No input is consumed.  The corresponding argument should be a pointer to
<b>int</b> into which the number of characters read from the input stream so
far by this call to <b><a href="./fioLib.html#sscanf">sscanf</a>(&nbsp;)</b> is written.  Execution of a %n directive does
not increment the assignment count returned when <b><a href="./fioLib.html#sscanf">sscanf</a>(&nbsp;)</b> completes
execution.
<dt>
<b>%</b>
<dd>
Matches a single <b>%</b>; no conversion or assignment occurs.  The
complete conversion specification is %%.
</dl>

<p>
If a conversion specification is invalid, the behavior is undefined.
<p>
The conversion specifiers <b>E</b>, <b>G</b>, and <b>X</b> are also valid and behave the
same as <b>e</b>, <b>g</b>, and <b>x</b>, respectively.
<p>
If end-of-file is encountered during input, conversion is terminated.  If 
end-of-file occurs before any characters matching the current directive
have been read (other than leading white space, where permitted), execution
of the current directive terminates with an input failure; otherwise, unless
execution of the current directive is terminated with a matching failure,
execution of the following directive (if any) is terminated with an input
failure.
<p>
If conversion terminates on a conflicting input character, the offending
input character is left unread in the input stream.  Trailing white space
(including new-line characters) is left unread unless matched by a
directive.  The success of literal matches and suppressed assignments is
not directly determinable other than via the %n directive.
<p>
</blockquote><h4>INCLUDE FILES</h4><blockquote><p>
<b>fioLib.h</b> 
<p>
</blockquote><h4>RETURNS</h4><blockquote><p>
<p>
The number of input items assigned, which can be fewer than provided for,
or even zero, in the event of an early matching failure; or EOF if an
input failure occurs before any conversion.
<p>
</blockquote><h4>SEE ALSO</h4><blockquote><p>
<b><a href="./fioLib.html#top">fioLib</a></b>, <b><a href="./ansiStdio.html#fscanf">fscanf</a>(&nbsp;)</b>, <b><a href="./ansiStdio.html#scanf">scanf</a>(&nbsp;)</b>,  
<i>American National Standard for Information Systems -</i>
<i>Programming Language - C, ANSI X3.159-1989: Input/Output (<b>stdio.h</b>)</i>
<p>

VARARGS2
</body>
</html>