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从www.CppReference.com打包的C++参考手册

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

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;stdio.h&gt;
  void perror( const char *str );
</pre>

  <p>The perror() function prints <em>str</em> and an
  implementation-defined error message corresponding to the global
  variable <em>errno</em>.  For example:</p>

  <pre class="example-code">
  char* input_filename = "not_found.txt";
  FILE* input = fopen( input_filename, "r" );
  if( input == NULL ) {
    char error_msg[255];
    sprintf( error_msg, "Error opening file '%s'", input_filename );
    perror( error_msg );
    exit( -1 );
  }
</pre>

  <p>The the file called <em>not_found.txt</em> is not found, this
  code will produce the following output:</p>

  <pre class="example-output">
  Error opening file 'not_found.txt': No such file or directory
</pre>

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    Related topics:
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    <a href="clearerr.html">clearerr</a><br>
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  <div class="name-format">
    printf
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;stdio.h&gt;
  int printf( const char *format, ... );
</pre>

  <p>The printf() function prints output to <strong>stdout</strong>,
  according to <em>format</em> and other arguments passed to printf().
  The string <em>format</em> consists of two types of items -
  characters that will be printed to the screen, and format commands
  that define how the other arguments to printf() are displayed.
  Basically, you specify a format string that has text in it, as well
  as &quot;special&quot; characters that map to the other arguments of
  printf(). For example, this code</p>
  <pre class="example-code">
   char name[20] = &quot;Bob&quot;;
   int age = 21;
   printf( &quot;Hello %s, you are %d years old\n&quot;, name, age );           
</pre>

  <p>displays the following output:</p>
  <pre class="example-code">
   Hello Bob, you are 21 years old              
</pre>

  <p>The %s means, &quot;insert the first argument, a string, right
  here.&quot; The %d indicates that the second argument (an integer)
  should be placed there. There are different %-codes for different
  variable types, as well as options to limit the length of the
  variables and whatnot.</p>

  <table class="code-table">
    <tr>
      <th class="code-table-th">Code</th>

      <th class="code-table-th">Format</th>
    </tr>

    <tr>
      <td class="code-table-td">%c</td>

      <td class="code-table-td">character</td>
    </tr>

    <tr>
      <td class="code-table-td">%d</td>

      <td class="code-table-td">signed integers</td>
    </tr>

    <tr>
      <td class="code-table-td">%i</td>

      <td class="code-table-td">signed integers</td>
    </tr>

    <tr>
      <td class="code-table-td">%e</td>

      <td class="code-table-td">scientific notation, with a lowercase
      &quot;e&quot;</td>
    </tr>

    <tr>
      <td class="code-table-td">%E</td>

      <td class="code-table-td">scientific notation, with a uppercase
      &quot;E&quot;</td>
    </tr>

    <tr>
      <td class="code-table-td">%f</td>

      <td class="code-table-td">floating point</td>
    </tr>

    <tr>
      <td class="code-table-td">%g</td>

      <td class="code-table-td">use %e or %f, whichever is shorter</td>
    </tr>

    <tr>
      <td class="code-table-td">%G</td>

      <td class="code-table-td">use %E or %f, whichever is shorter</td>
    </tr>

    <tr>
      <td class="code-table-td">%o</td>

      <td class="code-table-td">octal</td>
    </tr>

    <tr>
      <td class="code-table-td">%s</td>

      <td class="code-table-td">a string of characters</td>
    </tr>

    <tr>
      <td class="code-table-td">%u</td>

      <td class="code-table-td">unsigned integer</td>
    </tr>

    <tr>
      <td class="code-table-td">%x</td>

      <td class="code-table-td">unsigned hexadecimal, with lowercase
      letters</td>
    </tr>

    <tr>
      <td class="code-table-td">%X</td>

      <td class="code-table-td">unsigned hexadecimal, with uppercase
      letters</td>
    </tr>

    <tr>
      <td class="code-table-td">%p</td>

      <td class="code-table-td">a pointer</td>
    </tr>

    <tr>
      <td class="code-table-td">%n</td>

      <td class="code-table-td">the argument shall be a pointer to an
      integer into which is placed the number of characters written so
      far</td>
    </tr>

    <tr>
      <td class="code-table-td">%%</td>

      <td class="code-table-td">a &#39;%&#39; sign</td>
    </tr>
  </table>

  <p>An integer placed between a % sign and the format command acts as
  a minimum field width specifier, and pads the output with spaces or
  zeros to make it long enough. If you want to pad with zeros, place a
  zero before the minimum field width specifier:</p>
  <pre class="example-code">
   %012d                
</pre>

  <p>You can also include a precision modifier, in the form of a .N
  where N is some number, before the format command:</p>
  <pre class="example-code">
   %012.4d              
</pre>

  <p>The precision modifier has different meanings depending on the
  format command being used:</p>

  <ul>
    <li>With %e, %E, and %f, the precision modifier lets you specify
    the number of decimal places desired. For example, %12.6f will
    display a floating number at least 12 digits wide, with six decimal
    places.</li>

    <li>With %g and %G, the precision modifier determines the maximum
    number of significant digits displayed.</li>

    <li>With %s, the precision modifer simply acts as a maximumfield
    length, to complement the minimum field length that precedes the
    period.</li>
  </ul>

  <p>All of printf()&#39;s output is right-justified, unless you place
  a minus sign right after the % sign. For example,</p>
  <pre class="example-code">
   %-12.4f              
</pre>

  <p>will display a floating point number with a minimum of 12
  characters, 4 decimal places, and left justified. You may modify the
  %d, %i, %o, %u, and %x type specifiers with the letter l and the
  letter h to specify long and short <a href="../data_types.html">data
  types</a> (e.g. %hd means a short integer). The %e, %f, and %g type
  specifiers can have the letter l before them to indicate that a
  double follows. The %g, %f, and %e type specifiers can be preceded
  with the character &#39;#&#39; to ensure that the decimal point will
  be present, even if there are no decimal digits. The use of the
  &#39;#&#39; character with the %x type specifier indicates that the
  hexidecimal number should be printed with the &#39;0x&#39; prefix.
  The use of the &#39;#&#39; character with the %o type specifier
  indicates that the octal value should be displayed with a 0
  prefix.</p>

  <p>Inserting a plus sign '+' into the type specifier will force
  positive values to be preceded by a '+' sign.  Putting a space
  character ' ' there will force positive values to be preceded by a
  single space character.</p>

  <p>You can also include <a href="../escape_sequences.html">constant
  escape sequences</a> in the output string.</p>

  <p>The return value of printf() is the number of characters printed,
  or a negative number if an error occurred.</p>

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    Related topics:
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    <a href="fprintf.html">fprintf</a><br>
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  <div class="name-format">
    putc
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;stdio.h&gt;
  int putc( int ch, FILE *stream );
</pre>

  <p>The putc() function writes the character <em>ch</em> to
  <em>stream</em>. The return value is the character written, or
  <strong>EOF</strong> if there is an error. For example:</p>
  <pre class="example-code">
   int ch;
   FILE *input, *output;
   input = fopen( &quot;tmp.c&quot;, &quot;r&quot; );
   output = fopen( &quot;tmpCopy.c&quot;, &quot;w&quot; );
   ch = getc( input );
   while( ch != <strong>EOF</strong> ) {
     putc( ch, output );
     ch = getc( input );
   }
   fclose( input );
   fclose( output );            
</pre>

  <p>generates a copy of the file tmp.c called tmpCopy.c.</p>

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    <a href="feof.html">feof</a><br>
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    <a href="getc.html">getc</a><br>
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    <a href="putchar.html">putchar</a><br>
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  <div class="name-format">
    putchar
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;stdio.h&gt;
  int putchar( int ch );
</pre>

  <p>The putchar() function writes <em>ch</em> to
  <strong>stdout</strong>. The code</p>
  <pre class="example-code">
   putchar( ch );               
</pre>

  <p>is the same as</p>
  <pre class="example-code">
   putc( ch, <strong>stdout</strong> );         
</pre>

  <p>The return value of putchar() is the written character, or
  <strong>EOF</strong> if there is an error.</p>

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    Related topics:
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  <div class="name-format">
    puts
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;stdio.h&gt;
  int puts( char *str );
</pre>

  <p>The function puts() writes <em>str</em> to
  <strong>stdout</strong>. puts() returns non-negative on success, or
  <strong>EOF</strong> on failure.</p>

  <div class="related-name-format">
    Related topics:
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    <a href="fputs.html">fputs</a><br>
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  <div class="name-format">
    remove
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;stdio.h&gt;
  int remove( const char *fname );
</pre>

  <p>The remove() function erases the file specified by <em>fname</em>.
  The return value of remove() is zero upon success, and non-zero if
  there is an error.</p>

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    Related topics:
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    <a href="rename.html">rename</a>
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  <div class="name-format">
    rename
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;stdio.h&gt;
  int rename( const char *oldfname, const char *newfname );
</pre>

  <p>The function rename() changes the name of the file
  <em>oldfname</em> to <em>newfname</em>. The return value of rename()
  is zero upon success, non-zero on error.</p>

  <div class="related-name-format">
    Related topics:
  </div>

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    <a href="remove.html">remove</a>
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<hr>

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

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;stdio.h&gt;