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getline [C++ Reference]
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<h2><a name="getline" id="getline">getline</a></h2>
<div class="level2">
<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <string></span>
istream<span class="sy0">&</span> std<span class="sy0">::</span><span class="me2">getline</span><span class="br0">(</span> istream<span class="sy0">&</span> is<span class="sy0">,</span> string<span class="sy0">&</span> s <span class="br0">)</span><span class="sy0">;</span>
istream<span class="sy0">&</span> std<span class="sy0">::</span><span class="me2">getline</span><span class="br0">(</span> istream<span class="sy0">&</span> is<span class="sy0">,</span> string<span class="sy0">&</span> s<span class="sy0">,</span> Char delimiter <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
The C++ string header defines the global function getline() to read strings from
an I/O stream. The getline() function, which is not part of the string class,
reads a line from is and stores it into s. If a character delimiter is
specified, then getline() will use delimiter to decide when to stop reading
data. Otherwise, call the second form as follows:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw1">return</span> getline<span class="br0">(</span> is<span class="sy0">,</span> s<span class="sy0">,</span> is.<span class="me1">widen</span><span class="br0">(</span> <span class="st0">'<span class="es1">\n</span>'</span> <span class="br0">)</span> <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
NOTE: <code>istream</code> is the istream type <code>basic_istream<Char></code> according to the character type.
</p>
<p>
For example, the following code reads a line of text from stdin and displays it
to stdout:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw4">string</span> s<span class="sy0">;</span>
getline<span class="br0">(</span> cin<span class="sy0">,</span> s <span class="br0">)</span><span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="st0">"You entered "</span> <span class="sy0"><<</span> s <span class="sy0"><<</span> endl<span class="sy0">;</span></pre>
<p>
After getting a line of data in a string, you may find that <a href="../io/sstream/start.html" class="wikilink1" title="io:sstream:start">stringstreams</a> are
useful in extracting data from that string. For example, the following code
reads numbers from standard input, ignoring any “commented” lines that begin
with double slashes:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co1">// expects either space-delimited numbers or lines that start with</span>
<span class="co1">// two forward slashes (//)</span>
<span class="kw4">string</span> s<span class="sy0">;</span>
<span class="kw1">while</span><span class="br0">(</span> getline<span class="br0">(</span>cin<span class="sy0">,</span>s<span class="br0">)</span> <span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">if</span><span class="br0">(</span> s.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy0">>=</span> <span class="nu0">2</span> <span class="sy0">&&</span> s<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span> <span class="sy0">==</span> <span class="st0">'/'</span> <span class="sy0">&&</span> s<span class="br0">[</span><span class="nu0">1</span><span class="br0">]</span> <span class="sy0">==</span> <span class="st0">'/'</span> <span class="br0">)</span> <span class="br0">{</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="st0">" ignoring comment: "</span> <span class="sy0"><<</span> s <span class="sy0"><<</span> endl<span class="sy0">;</span>
<span class="br0">}</span> <span class="kw1">else</span> <span class="br0">{</span>
istringstream ss<span class="br0">(</span>s<span class="br0">)</span><span class="sy0">;</span>
<span class="kw4">double</span> d<span class="sy0">;</span>
<span class="kw1">while</span><span class="br0">(</span> ss <span class="sy0">>></span> d <span class="br0">)</span> <span class="br0">{</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="st0">" got a number: "</span> <span class="sy0"><<</span> d <span class="sy0"><<</span> endl<span class="sy0">;</span>
<span class="br0">}</span>
<span class="br0">}</span>
<span class="br0">}</span></pre>
<p>
When run with a user supplying input, the above code might produce this output:
</p>
<pre class="code">
// test
ignoring comment: // test
23.3 -1 3.14159
got a number: 23.3
got a number: -1
got a number: 3.14159
// next batch
ignoring comment: // next batch
1 2 3 4 5
got a number: 1
got a number: 2
got a number: 3
got a number: 4
got a number: 5
50
got a number: 50</pre>
<p>
Because the getline() function begins reading at the current file position, it can also
be used to read the remainder of a line, or any characters up to the specified delimiter.
</p>
<p>
Related Topics: <a href="../io/get.html" class="wikilink1" title="io:get">get</a>, <a href="../io/getline.html" class="wikilink1" title="io:getline">getline</a>, <a href="../io/sstream/start.html" class="wikilink1" title="io:sstream:start">stringstream</a>
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