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  93 <li class="toctree-l3 current"><a class="current reference internal" href="#">Incrementing and Decrementing Values</a></li>
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 164       <li>Incrementing and Decrementing Values</li>
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 171               <a href="https://github.com/m6w6/libmemcached/blob/v1.x/docs/source/libmemcached/memcached_auto.rst" class="fa fa-github"> Edit on GitHub</a>
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 184
 185   <div class="section" id="incrementing-and-decrementing-values">
 186 <h1>Incrementing and Decrementing Values<a class="headerlink" href="#incrementing-and-decrementing-values" title="Permalink to this headline">¶</a></h1>
 187 <div class="section" id="synopsis">
 188 <h2>SYNOPSIS<a class="headerlink" href="#synopsis" title="Permalink to this headline">¶</a></h2>
 189 <dl class="docutils">
 190 <dt>#include &lt;libmemcached/memcached.h&gt;</dt>
 191 <dd>Compile and link with -lmemcached</dd>
 192 </dl>
 193 <dl class="function">
 194 <dt id="_CPPv419memcached_incrementP12memcached_stPKc6size_t8uint32_tP8uint64_t">
 195 <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>
 196 <dd></dd></dl>
 197
 198 <dl class="function">
 199 <dt id="_CPPv419memcached_decrementP12memcached_stPKc6size_t8uint32_tP8uint64_t">
 200 <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>
 201 <dd></dd></dl>
 202
 203 <dl class="function">
 204 <dt id="_CPPv432memcached_increment_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 205 <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>
 206 <dd></dd></dl>
 207
 208 <dl class="function">
 209 <dt id="_CPPv432memcached_decrement_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 210 <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>
 211 <dd></dd></dl>
 212
 213 <dl class="function">
 214 <dt id="_CPPv426memcached_increment_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t">
 215 <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>
 216 <dd></dd></dl>
 217
 218 <dl class="function">
 219 <dt id="_CPPv426memcached_decrement_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t">
 220 <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>
 221 <dd></dd></dl>
 222
 223 <dl class="function">
 224 <dt id="_CPPv439memcached_increment_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 225 <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>
 226 <dd></dd></dl>
 227
 228 <dl class="function">
 229 <dt id="_CPPv439memcached_decrement_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 230 <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>
 231 <dd><table class="docutils field-list" frame="void" rules="none">
 232 <col class="field-name" />
 233 <col class="field-body" />
 234 <tbody valign="top">
 235 <tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
 236 <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>
 237 <li><strong>group_key</strong> -- key namespace</li>
 238 <li><strong>group_key_length</strong> -- length of the key namespace without any terminating zero</li>
 239 <li><strong>key</strong> -- the key</li>
 240 <li><strong>key_length</strong> -- length of the key without any terminating zero</li>
 241 <li><strong>offset</strong> -- offset to increment/decrement</li>
 242 <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>
 243 <li><strong>expiration</strong> -- expiration as a unix timestamp or as relative expiration time in seconds</li>
 244 <li><strong>value</strong> -- the resulting value after initialization/increment/decrement</li>
 245 </ul>
 246 </td>
 247 </tr>
 248 <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>
 249 </td>
 250 </tr>
 251 </tbody>
 252 </table>
 253 </dd></dl>
 254
 255 </div>
 256 <div class="section" id="description">
 257 <h2>DESCRIPTION<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
 258 <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
 259 (overflow and underflow are not detected). This gives you the ability to use
 260 memcached to generate shared sequences of values.</p>
 261 <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
 262 value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. The value is then returned via the
 263 uint32_t <code class="docutils literal notranslate"><span class="pre">value</span></code> pointer you pass to it.</p>
 264 <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
 265 value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. The value is then returned via the
 266 uint32_t <code class="docutils literal notranslate"><span class="pre">value</span></code> pointer you pass to it.</p>
 267 <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
 268 increments the value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. If the object specified by
 269 <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>
 270 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
 271 all other <code class="docutils literal notranslate"><span class="pre">expiration</span></code> values, the operation will succeed by seeding the value
 272 for that key with a initial value to expire with the provided expiration time.
 273 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
 274 <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
 275 available when using the binary protocol.</p>
 276 <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
 277 decrements the value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. If the object specified by
 278 <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>
 279 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
 280 all other <code class="docutils literal notranslate"><span class="pre">expiration</span></code> values, the operation will succeed by seeding the value
 281 for that key with a initial value to expire with the provided expiration time.
 282 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
 283 <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
 284 available when using the binary protocol.</p>
 285 <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>,
 286 <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
 287 <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
 288 above.</p>
 289 </div>
 290 <div class="section" id="return-value">
 291 <h2>RETURN VALUE<a class="headerlink" href="#return-value" title="Permalink to this headline">¶</a></h2>
 292 <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.
 293 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>.
 294 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>
 295 </div>
 296 <div class="section" id="see-also">
 297 <h2>SEE ALSO<a class="headerlink" href="#see-also" title="Permalink to this headline">¶</a></h2>
 298 <ul class="simple">
 299 <li><em class="manpage"><a class="manpage reference external" href="https://linux.die.net/man/1/memcached">memcached(1)</a></em></li>
 300 <li><a class="reference internal" href="../libmemcached.html"><span class="doc">C/C++ Client Library for memcached</span></a></li>
 301 <li><a class="reference internal" href="memcached_strerror.html"><span class="doc">Converting Error Codes to Messages</span></a></li>
 302 </ul>
 303 </div>
 304 </div>
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