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从www.CppReference.com打包的C++参考手册

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  <div class="name-format">
    flush
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  ostream&amp; flush();
</pre>

  <p>The flush() function causes the buffer for the current output
  stream to be actually written out to the attached device.</p>

  <p>This function is useful for printing out debugging information,
  because sometimes programs abort before they have a chance to write
  their output buffers to the screen. Judicious use of flush() can
  ensure that all of your debugging statements actually get
  printed.</p>

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  <div class="name-format">
    gcount
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  streamsize gcount();
</pre>

  <p>The function gcount() is used with input streams, and returns the
  number of characters read by the last input operation.</p>

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    <a href="get.html">get</a><br>
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  <div class="name-format">
    get
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  int get();
  istream&amp; get( char&amp; ch );
  istream&amp; get( char* buffer, streamsize num );
  istream&amp; get( char* buffer, streamsize num, char delim );
  istream&amp; get( streambuf&amp; buffer );
  istream&amp; get( streambuf&amp; buffer, char delim );
</pre>

  <p>The get() function is used with input streams, and either:</p>

  <ul>
    <li>reads a character and returns that value,</li>

    <li>reads a character and stores it as <em>ch</em>,</li>

    <li>reads characters into <em>buffer</em> until <em>num</em> - 1
    characters have been read, or <strong>EOF</strong> or newline
    encountered,</li>

    <li>reads characters into <em>buffer</em> until <em>num</em> - 1
    characters have been read, or <strong>EOF</strong> or the
    <em>delim</em> character encountered (<em>delim</em> is not read
    until next time),</li>

    <li>reads characters into buffer until a newline or
    <strong>EOF</strong> is encountered,</li>

    <li>or reads characters into buffer until a newline,
    <strong>EOF</strong>, or <em>delim</em> character is encountered
    (again, <em>delim</em> isn&#39;t read until the next get() ).</li>
  </ul>

  <p>For example, the following code displays the contents of a file
  called temp.txt, character by character:</p>
  <pre class="example-code">
   char ch;
   ifstream fin( &quot;temp.txt&quot; );
   while( fin.get(ch) )
     cout &lt;&lt; ch;
   fin.close();         
</pre>

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    <a href="gcount.html">gcount</a><br>
    <a href="getline.html">getline</a><br>
    (C++ Strings) <a href="../cppstring/getline.html">getline</a><br>
    <a href="ignore.html">ignore</a><br>
    <a href="peek.html">peek</a><br>
    <a href="put.html">put</a><br>
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<hr>

  <div class="name-format">
    getline
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  istream&amp; getline( char* buffer, streamsize num );
  istream&amp; getline( char* buffer, streamsize num, char delim );
</pre>

  <p>The getline() function is used with input streams, and reads
  characters into <em>buffer</em> until either:</p>

  <ul>
    <li><em>num</em> - 1 characters have been read,</li>

    <li>a newline is encountered,</li>

    <li>an <strong>EOF</strong> is encountered,</li>

    <li>or, optionally, until the character <em>delim</em> is read. The
    <em>delim</em> character is not put into buffer.</li>
  </ul>

  <p>For example, the following code uses the getline function to
  display the first 100 characters from each line of a text file:</p>

  <pre class="example-code">
  ifstream fin("tmp.dat");

  int MAX_LENGTH = 100;
  char line[MAX_LENGTH];

  while( fin.getline(line, MAX_LENGTH) ) {
    cout << "read line: " << line << endl;
  }
</pre>

  <p>If you'd like to read lines from a file into <a
  href="../cppstring/index.html">strings</a> instead of character arrays,
  consider using the <a href="../cppstring/getline.html">string
  getline</a> function.</p>

  <p>Those using a Microsoft compiler may find that getline() reads an
  extra character, and should consult the documentation on the <a href=
  "http://support.microsoft.com/default.aspx?scid=kb;EN-US;q240015">Microsoft
  getline bug</a>.</p>

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  <div class="name-format">
    good
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  bool good();
</pre>

  <p>The function good() returns true if no errors have occurred with
  the current stream, false otherwise.</p>

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  <div class="name-format">
    ignore
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  istream&amp; ignore( streamsize num=1, int delim=<strong>EOF</strong> );
</pre>

  <p>The ignore() function is used with input streams. It reads and
  throws away characters until <em>num</em> characters have been read
  (where <em>num</em> defaults to 1) or until the character
  <em>delim</em> is read (where <em>delim</em> defaults to
  <strong>EOF</strong>).</p>

  <p>The ignore() function can sometimes be useful when using the
  getline() function together with the &gt;&gt; operator.  For
  example, if you read some input that is followed by a newline using
  the &gt;&gt; operator, the newline will remain in the input as the
  next thing to be read.  Since getline() will by default stop reading
  input when it reaches a newline, a subsequent call to getline() will
  return an empty string.  In this case, the ignore() function could
  be called before getline() to "throw away" the newline.</p>

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  <div class="name-format">
    open
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  void open( const char *filename );
  void open( const char *filename, openmode mode = default_mode );
</pre>

  <p>The function open() is used with file streams. It opens
  <em>filename</em> and associates it with the current stream. The
  optional <a href="../io_flags.html#mode_flags">io stream mode
  flag</a> <em>mode</em> defaults to ios::in for ifstream, ios::out for
  ofstream, and ios::in|ios::out for fstream.</p>

  <p>If open() fails, the resulting stream will evaluate to false when
  used in a Boolean expression. For example:</p>
  <pre class="example-code">
 ifstream inputStream;
 inputStream.open(&quot;file.txt&quot;);
 if( !inputStream ) {
   cerr &lt;&lt; &quot;Error opening input stream&quot; &lt;&lt; endl;
   return;
 }              
</pre>

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<hr>

  <div class="name-format">
    peek
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  int peek();
</pre>

  <p>The function peek() is used with input streams, and returns the
  next character in the stream or <strong>EOF</strong> if the end of
  file is read. peek() does not remove the character from the
  stream.</p>

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  <div class="name-format">
    precision
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  streamsize precision();
  streamsize precision( streamsize p );
</pre>

  <p>The precision() function either sets or returns the current number
  of digits that is displayed for floating-point variables.</p>

  <p>For example, the following code sets the precision of the cout
  stream to 5:</p>
  <pre class="example-code">
   float num = 314.15926535;
   cout.precision( 5 );
   cout &lt;&lt; num;           
</pre>

  <p>This code displays the following output:</p>
  <pre class="example-code">
   314.16               
</pre>

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  <div class="name-format">
    put
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;fstream&gt;
  ostream&amp; put( char ch );
</pre>

  <p>The function put() is used with output streams, and writes the
  character <em>ch</em> to the stream.</p>

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