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  94 <li class="toctree-l3 current"><a class="current reference internal" href="#">Incrementing and Decrementing Values</a></li>
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 193   <div class="section" id="incrementing-and-decrementing-values">
 194 <h1>Incrementing and Decrementing Values<a class="headerlink" href="#incrementing-and-decrementing-values" title="Permalink to this headline">¶</a></h1>
 195 <div class="section" id="synopsis">
 196 <h2>SYNOPSIS<a class="headerlink" href="#synopsis" title="Permalink to this headline">¶</a></h2>
 197 <dl class="docutils">
 198 <dt>#include &lt;libmemcached/memcached.h&gt;</dt>
 199 <dd>Compile and link with -lmemcached</dd>
 200 </dl>
 201 <dl class="function">
 202 <dt id="_CPPv419memcached_incrementP12memcached_stPKc6size_t8uint32_tP8uint64_t">
 203 <span id="_CPPv319memcached_incrementP12memcached_stPKc6size_t8uint32_tP8uint64_t"></span><span id="_CPPv219memcached_incrementP12memcached_stPKc6size_t8uint32_tP8uint64_t"></span><span id="memcached_increment__memcached_stP.cCP.s.uint32_t.uint64_tP"></span><a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t">memcached_return_t</a> <code class="descname">memcached_increment</code><span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *<em>ptr</em>, <em class="property">const</em> char *<em>key</em>, size_t <em>key_length</em>, uint32_t <em>offset</em>, uint64_t *<em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv419memcached_incrementP12memcached_stPKc6size_t8uint32_tP8uint64_t" title="Permalink to this definition">¶</a><br /></dt>
 204 <dd></dd></dl>
 205
 206 <dl class="function">
 207 <dt id="_CPPv419memcached_decrementP12memcached_stPKc6size_t8uint32_tP8uint64_t">
 208 <span id="_CPPv319memcached_decrementP12memcached_stPKc6size_t8uint32_tP8uint64_t"></span><span id="_CPPv219memcached_decrementP12memcached_stPKc6size_t8uint32_tP8uint64_t"></span><span id="memcached_decrement__memcached_stP.cCP.s.uint32_t.uint64_tP"></span><a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t">memcached_return_t</a> <code class="descname">memcached_decrement</code><span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *<em>ptr</em>, <em class="property">const</em> char *<em>key</em>, size_t <em>key_length</em>, uint32_t <em>offset</em>, uint64_t *<em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv419memcached_decrementP12memcached_stPKc6size_t8uint32_tP8uint64_t" title="Permalink to this definition">¶</a><br /></dt>
 209 <dd></dd></dl>
 210
 211 <dl class="function">
 212 <dt id="_CPPv432memcached_increment_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 213 <span id="_CPPv332memcached_increment_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t"></span><span id="_CPPv232memcached_increment_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t"></span><span id="memcached_increment_with_initial__memcached_stP.cCP.s.uint64_t.uint64_t.time_t.uint64_tP"></span><a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t">memcached_return_t</a> <code class="descname">memcached_increment_with_initial</code><span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *<em>ptr</em>, <em class="property">const</em> char *<em>key</em>, size_t <em>key_length</em>, uint64_t <em>offset</em>, uint64_t <em>initial</em>, time_t <em>expiration</em>, uint64_t *<em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv432memcached_increment_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="Permalink to this definition">¶</a><br /></dt>
 214 <dd></dd></dl>
 215
 216 <dl class="function">
 217 <dt id="_CPPv432memcached_decrement_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 218 <span id="_CPPv332memcached_decrement_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t"></span><span id="_CPPv232memcached_decrement_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t"></span><span id="memcached_decrement_with_initial__memcached_stP.cCP.s.uint64_t.uint64_t.time_t.uint64_tP"></span><a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t">memcached_return_t</a> <code class="descname">memcached_decrement_with_initial</code><span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *<em>ptr</em>, <em class="property">const</em> char *<em>key</em>, size_t <em>key_length</em>, uint64_t <em>offset</em>, uint64_t <em>initial</em>, time_t <em>expiration</em>, uint64_t *<em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv432memcached_decrement_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="Permalink to this definition">¶</a><br /></dt>
 219 <dd></dd></dl>
 220
 221 <dl class="function">
 222 <dt id="_CPPv426memcached_increment_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t">
 223 <span id="_CPPv326memcached_increment_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t"></span><span id="_CPPv226memcached_increment_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t"></span><span id="memcached_increment_by_key__memcached_stP.cCP.s.cCP.s.uint32_t.uint64_tP"></span><a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t">memcached_return_t</a> <code class="descname">memcached_increment_by_key</code><span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *<em>ptr</em>, <em class="property">const</em> char *<em>group_key</em>, size_t <em>group_key_length</em>, <em class="property">const</em> char *<em>key</em>, size_t <em>key_length</em>, uint32_t <em>offset</em>, uint64_t *<em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv426memcached_increment_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t" title="Permalink to this definition">¶</a><br /></dt>
 224 <dd></dd></dl>
 225
 226 <dl class="function">
 227 <dt id="_CPPv426memcached_decrement_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t">
 228 <span id="_CPPv326memcached_decrement_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t"></span><span id="_CPPv226memcached_decrement_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t"></span><span id="memcached_decrement_by_key__memcached_stP.cCP.s.cCP.s.uint32_t.uint64_tP"></span><a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t">memcached_return_t</a> <code class="descname">memcached_decrement_by_key</code><span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *<em>ptr</em>, <em class="property">const</em> char *<em>group_key</em>, size_t <em>group_key_length</em>, <em class="property">const</em> char *<em>key</em>, size_t <em>key_length</em>, uint32_t <em>offset</em>, uint64_t *<em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv426memcached_decrement_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t" title="Permalink to this definition">¶</a><br /></dt>
 229 <dd></dd></dl>
 230
 231 <dl class="function">
 232 <dt id="_CPPv439memcached_increment_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 233 <span id="_CPPv339memcached_increment_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t"></span><span id="_CPPv239memcached_increment_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t"></span><span id="memcached_increment_with_initial_by_key__memcached_stP.cCP.s.cCP.s.uint64_t.uint64_t.time_t.uint64_tP"></span><a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t">memcached_return_t</a> <code class="descname">memcached_increment_with_initial_by_key</code><span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *<em>ptr</em>, <em class="property">const</em> char *<em>group_key</em>, size_t <em>group_key_length</em>, <em class="property">const</em> char *<em>key</em>, size_t <em>key_length</em>, uint64_t <em>offset</em>, uint64_t <em>initial</em>, time_t <em>expiration</em>, uint64_t *<em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv439memcached_increment_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="Permalink to this definition">¶</a><br /></dt>
 234 <dd></dd></dl>
 235
 236 <dl class="function">
 237 <dt id="_CPPv439memcached_decrement_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 238 <span id="_CPPv339memcached_decrement_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t"></span><span id="_CPPv239memcached_decrement_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t"></span><span id="memcached_decrement_with_initial_by_key__memcached_stP.cCP.s.cCP.s.uint64_t.uint64_t.time_t.uint64_tP"></span><a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t">memcached_return_t</a> <code class="descname">memcached_decrement_with_initial_by_key</code><span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *<em>ptr</em>, <em class="property">const</em> char *<em>group_key</em>, size_t <em>group_key_length</em>, <em class="property">const</em> char *<em>key</em>, size_t <em>key_length</em>, uint64_t <em>offset</em>, uint64_t <em>initial</em>, time_t <em>expiration</em>, uint64_t *<em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv439memcached_decrement_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="Permalink to this definition">¶</a><br /></dt>
 239 <dd><table class="docutils field-list" frame="void" rules="none">
 240 <col class="field-name" />
 241 <col class="field-body" />
 242 <tbody valign="top">
 243 <tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
 244 <li><strong>ptr</strong> -- pointer to an initialized <a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_st</span></code></a> struct</li>
 245 <li><strong>group_key</strong> -- key namespace</li>
 246 <li><strong>group_key_length</strong> -- length of the key namespace without any terminating zero</li>
 247 <li><strong>key</strong> -- the key</li>
 248 <li><strong>key_length</strong> -- length of the key without any terminating zero</li>
 249 <li><strong>offset</strong> -- offset to increment/decrement</li>
 250 <li><strong>initial</strong> -- initial value if <a class="reference internal" href="#_CPPv439memcached_decrement_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="memcached_decrement_with_initial_by_key::key"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">key</span></code></a> does not exist and <a class="reference internal" href="#_CPPv439memcached_decrement_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="memcached_decrement_with_initial_by_key::expiration"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">expiration</span></code></a> is not <code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_EXPIRATION_NOT_ADD</span></code></li>
 251 <li><strong>expiration</strong> -- expiration as a unix timestamp or as relative expiration time in seconds</li>
 252 <li><strong>value</strong> -- the resulting value after initialization/increment/decrement</li>
 253 </ul>
 254 </td>
 255 </tr>
 256 <tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first last"><a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_return_t</span></code></a> indicating success</p>
 257 </td>
 258 </tr>
 259 </tbody>
 260 </table>
 261 </dd></dl>
 262
 263 </div>
 264 <div class="section" id="description">
 265 <h2>DESCRIPTION<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
 266 <p><em class="manpage"><a class="manpage reference external" href="https://linux.die.net/man/1/memcached">memcached(1)</a></em> servers have the ability to increment and decrement keys
 267 (overflow and underflow are not detected). This gives you the ability to use
 268 memcached to generate shared sequences of values.</p>
 269 <p><a class="reference internal" href="#_CPPv419memcached_incrementP12memcached_stPKc6size_t8uint32_tP8uint64_t" title="memcached_increment"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_increment()</span></code></a> takes a <code class="docutils literal notranslate"><span class="pre">key</span></code> and <code class="docutils literal notranslate"><span class="pre">key_length</span></code> and increments the
 270 value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. The value is then returned via the
 271 uint32_t <code class="docutils literal notranslate"><span class="pre">value</span></code> pointer you pass to it.</p>
 272 <p><a class="reference internal" href="#_CPPv419memcached_decrementP12memcached_stPKc6size_t8uint32_tP8uint64_t" title="memcached_decrement"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_decrement()</span></code></a> takes a <code class="docutils literal notranslate"><span class="pre">key</span></code> and <code class="docutils literal notranslate"><span class="pre">key_length</span></code> and decrements the
 273 value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. The value is then returned via the
 274 uint32_t <code class="docutils literal notranslate"><span class="pre">value</span></code> pointer you pass to it.</p>
 275 <p><a class="reference internal" href="#_CPPv432memcached_increment_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="memcached_increment_with_initial"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_increment_with_initial()</span></code></a> takes a <code class="docutils literal notranslate"><span class="pre">key</span></code> and <code class="docutils literal notranslate"><span class="pre">key_length</span></code> and
 276 increments the value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. If the object specified by
 277 <code class="docutils literal notranslate"><span class="pre">key</span></code> does not exist, one of two things may happen: If the <code class="docutils literal notranslate"><span class="pre">expiration</span></code>
 278 value is <a class="reference internal" href="constants.html#c.MEMCACHED_EXPIRATION_NOT_ADD" title="MEMCACHED_EXPIRATION_NOT_ADD"><code class="xref c c-macro docutils literal notranslate"><span class="pre">MEMCACHED_EXPIRATION_NOT_ADD</span></code></a>, the operation will fail. For
 279 all other <code class="docutils literal notranslate"><span class="pre">expiration</span></code> values, the operation will succeed by seeding the value
 280 for that key with a initial value to expire with the provided expiration time.
 281 The <code class="docutils literal notranslate"><span class="pre">flags</span></code> will be set to zero. The value is then returned via the uint32_t
 282 <code class="docutils literal notranslate"><span class="pre">value</span></code> pointer you pass to it. <code class="docutils literal notranslate"><span class="pre">memcached_increment_with_initial</span></code> is only
 283 available when using the binary protocol.</p>
 284 <p><a class="reference internal" href="#_CPPv432memcached_decrement_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="memcached_decrement_with_initial"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_decrement_with_initial()</span></code></a> takes a <code class="docutils literal notranslate"><span class="pre">key</span></code> and <code class="docutils literal notranslate"><span class="pre">key_length</span></code> and
 285 decrements the value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. If the object specified by
 286 <code class="docutils literal notranslate"><span class="pre">key</span></code> does not exist, one of two things may happen: If the <code class="docutils literal notranslate"><span class="pre">expiration</span></code>
 287 value is <a class="reference internal" href="constants.html#c.MEMCACHED_EXPIRATION_NOT_ADD" title="MEMCACHED_EXPIRATION_NOT_ADD"><code class="xref c c-macro docutils literal notranslate"><span class="pre">MEMCACHED_EXPIRATION_NOT_ADD</span></code></a>, the operation will fail. For
 288 all other <code class="docutils literal notranslate"><span class="pre">expiration</span></code> values, the operation will succeed by seeding the value
 289 for that key with a initial value to expire with the provided expiration time.
 290 The <code class="docutils literal notranslate"><span class="pre">flags</span></code> will be set to zero. The value is then returned via the uint32_t
 291 <code class="docutils literal notranslate"><span class="pre">value</span></code> pointer you pass to it. <a class="reference internal" href="#_CPPv432memcached_decrement_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="memcached_decrement_with_initial"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_decrement_with_initial()</span></code></a> is only
 292 available when using the binary protocol.</p>
 293 <p><a class="reference internal" href="#_CPPv426memcached_increment_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t" title="memcached_increment_by_key"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_increment_by_key()</span></code></a>, <a class="reference internal" href="#_CPPv426memcached_decrement_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t" title="memcached_decrement_by_key"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_decrement_by_key()</span></code></a>,
 294 <a class="reference internal" href="#_CPPv439memcached_increment_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="memcached_increment_with_initial_by_key"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_increment_with_initial_by_key()</span></code></a>, and
 295 <a class="reference internal" href="#_CPPv439memcached_decrement_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t" title="memcached_decrement_with_initial_by_key"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_decrement_with_initial_by_key()</span></code></a> are master key equivalents of the
 296 above.</p>
 297 </div>
 298 <div class="section" id="return-value">
 299 <h2>RETURN VALUE<a class="headerlink" href="#return-value" title="Permalink to this headline">¶</a></h2>
 300 <p>A value of type <a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_return_t</span></code></a>  is returned.
 301 On success that value will be <a class="reference internal" href="memcached_return_t.html#_CPPv4N18memcached_return_t17MEMCACHED_SUCCESSE" title="MEMCACHED_SUCCESS"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_SUCCESS</span></code></a>.
 302 Use <a class="reference internal" href="memcached_strerror.html#_CPPv418memcached_strerrorP12memcached_st18memcached_return_t" title="memcached_strerror"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_strerror()</span></code></a> to translate this value to a printable string.</p>
 303 </div>
 304 <div class="section" id="see-also">
 305 <h2>SEE ALSO<a class="headerlink" href="#see-also" title="Permalink to this headline">¶</a></h2>
 306 <ul class="simple">
 307 <li><em class="manpage"><a class="manpage reference external" href="https://linux.die.net/man/1/memcached">memcached(1)</a></em></li>
 308 <li><a class="reference internal" href="../libmemcached.html"><span class="doc">C/C++ Client Library for memcached</span></a></li>
 309 <li><a class="reference internal" href="memcached_strerror.html"><span class="doc">Converting Error Codes to Messages</span></a></li>
 310 </ul>
 311 </div>
 312 </div>
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