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scanf [C++ Reference]
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<h2><a name="scanf" id="scanf">scanf</a></h2>
<div class="level2">
<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <cstdio></span>
<span class="kw4">int</span> scanf<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy0">*</span>format<span class="sy0">,</span> ... <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
The scanf() function reads input from stdin, according to the given format, and
stores the data in the other arguments. It works a lot like printf().
</p>
<p>
The format string consists of control characters, whitespace characters, and non-
whitespace characters. The control characters are preceded by a % sign, and are
as follows:
</p>
<table class="inline">
<tr class="row0">
<th class="col0">Control Character</th><th class="col1">Explanation</th>
</tr>
<tr class="row1">
<td class="col0">%c</td><td class="col1">a single character</td>
</tr>
<tr class="row2">
<td class="col0">%d</td><td class="col1">a decimal integer</td>
</tr>
<tr class="row3">
<td class="col0">%i</td><td class="col1">an integer</td>
</tr>
<tr class="row4">
<td class="col0">%e, %f, %g</td><td class="col1">a floating-point number</td>
</tr>
<tr class="row5">
<td class="col0">%lf</td><td class="col1">a double</td>
</tr>
<tr class="row6">
<td class="col0">%o</td><td class="col1">an octal number</td>
</tr>
<tr class="row7">
<td class="col0">%s</td><td class="col1">a string</td>
</tr>
<tr class="row8">
<td class="col0">%x</td><td class="col1">a hexadecimal number</td>
</tr>
<tr class="row9">
<td class="col0">%p</td><td class="col1">a pointer</td>
</tr>
<tr class="row10">
<td class="col0">%n</td><td class="col1">an integer equal to the number of characters read so far</td>
</tr>
<tr class="row11">
<td class="col0">%u</td><td class="col1">an unsigned integer</td>
</tr>
<tr class="row12">
<td class="col0">%[]</td><td class="col1">a set of characters</td>
</tr>
<tr class="row13">
<td class="col0">%%</td><td class="col1">a percent sign</td>
</tr>
</table>
<p>
scanf() reads the input, matching the characters from format. When a control
character is read, it puts the value in the next variable. Whitespace (tabs,
spaces, etc) are skipped. Non-whitespace characters are matched to the input,
then discarded. If a number comes between the % sign and the control character,
then only that many characters will be converted into the variable. If scanf()
encounters a set of characters, denoted by the %[] control character, then any
characters found within the brackets are read into the variable. The return
value of scanf() is the number of variables that were successfully assigned
values, or <acronym title="End of file">EOF</acronym> if there is an error.
</p>
<p>
The following code snippet uses scanf() to read an int, float, and a double from the
user. Note that the variable arguments to scanf() are passed in by address, as
denoted by the ampersand (&) preceding each variable:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw4">int</span> i<span class="sy0">;</span>
<span class="kw4">float</span> f<span class="sy0">;</span>
<span class="kw4">double</span> d<span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">(</span> <span class="st0">"Enter an integer: "</span> <span class="br0">)</span><span class="sy0">;</span>
scanf<span class="br0">(</span> <span class="st0">"%d"</span><span class="sy0">,</span> <span class="sy0">&</span>i <span class="br0">)</span><span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">(</span> <span class="st0">"Enter a float: "</span> <span class="br0">)</span><span class="sy0">;</span>
scanf<span class="br0">(</span> <span class="st0">"%f"</span><span class="sy0">,</span> <span class="sy0">&</span>f <span class="br0">)</span><span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">(</span> <span class="st0">"Enter a double: "</span> <span class="br0">)</span><span class="sy0">;</span>
scanf<span class="br0">(</span> <span class="st0">"%lf"</span><span class="sy0">,</span> <span class="sy0">&</span>d <span class="br0">)</span><span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">(</span> <span class="st0">"You entered %d, %f, and %f<span class="es1">\n</span>"</span><span class="sy0">,</span> i<span class="sy0">,</span> f<span class="sy0">,</span> d <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
Related Topics: <a href="../../c/io/fgets.html" class="wikilink1" title="c:io:fgets">fgets</a>, <a href="../../c/io/fscanf.html" class="wikilink1" title="c:io:fscanf">fscanf</a>, <a href="../../c/io/printf.html" class="wikilink1" title="c:io:printf">printf</a>, <a href="../../c/io/sscanf.html" class="wikilink1" title="c:io:sscanf">sscanf</a>
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