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  96 <li class="toctree-l3 current"><a class="current reference internal" href="#">Incrementing and Decrementing Values</a></li>
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 196   <div class="section" id="incrementing-and-decrementing-values">
 197 <h1>Incrementing and Decrementing Values<a class="headerlink" href="#incrementing-and-decrementing-values" title="Permalink to this headline">¶</a></h1>
 198 <div class="section" id="synopsis">
 199 <h2>SYNOPSIS<a class="headerlink" href="#synopsis" title="Permalink to this headline">¶</a></h2>
 200 <dl class="simple">
 201 <dt>#include &lt;libmemcached/memcached.h&gt;</dt><dd><p>Compile and link with -lmemcached</p>
 202 </dd>
 203 </dl>
 204 <dl class="cpp function">
 205 <dt id="_CPPv419memcached_incrementP12memcached_stPKc6size_t8uint32_tP8uint64_t">
 206 <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="sig-name 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>
 207 <dd></dd></dl>
 208
 209 <dl class="cpp function">
 210 <dt id="_CPPv419memcached_decrementP12memcached_stPKc6size_t8uint32_tP8uint64_t">
 211 <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="sig-name 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>
 212 <dd></dd></dl>
 213
 214 <dl class="cpp function">
 215 <dt id="_CPPv432memcached_increment_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 216 <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="sig-name 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>
 217 <dd></dd></dl>
 218
 219 <dl class="cpp function">
 220 <dt id="_CPPv432memcached_decrement_with_initialP12memcached_stPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 221 <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="sig-name 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>
 222 <dd></dd></dl>
 223
 224 <dl class="cpp function">
 225 <dt id="_CPPv426memcached_increment_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t">
 226 <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="sig-name 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>
 227 <dd></dd></dl>
 228
 229 <dl class="cpp function">
 230 <dt id="_CPPv426memcached_decrement_by_keyP12memcached_stPKc6size_tPKc6size_t8uint32_tP8uint64_t">
 231 <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="sig-name 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>
 232 <dd></dd></dl>
 233
 234 <dl class="cpp function">
 235 <dt id="_CPPv439memcached_increment_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 236 <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="sig-name 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>
 237 <dd></dd></dl>
 238
 239 <dl class="cpp function">
 240 <dt id="_CPPv439memcached_decrement_with_initial_by_keyP12memcached_stPKc6size_tPKc6size_t8uint64_t8uint64_t6time_tP8uint64_t">
 241 <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="sig-name 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>
 242 <dd><dl class="field-list simple">
 243 <dt class="field-odd">Parameters</dt>
 244 <dd class="field-odd"><ul class="simple">
 245 <li><p><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</p></li>
 246 <li><p><strong>group_key</strong> -- key namespace</p></li>
 247 <li><p><strong>group_key_length</strong> -- length of the key namespace without any terminating zero</p></li>
 248 <li><p><strong>key</strong> -- the key</p></li>
 249 <li><p><strong>key_length</strong> -- length of the key without any terminating zero</p></li>
 250 <li><p><strong>offset</strong> -- offset to increment/decrement</p></li>
 251 <li><p><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></p></li>
 252 <li><p><strong>expiration</strong> -- expiration as a unix timestamp or as relative expiration time in seconds</p></li>
 253 <li><p><strong>value</strong> -- the resulting value after initialization/increment/decrement</p></li>
 254 </ul>
 255 </dd>
 256 <dt class="field-even">Returns</dt>
 257 <dd class="field-even"><p><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>
 258 </dd>
 259 </dl>
 260 </dd></dl>
 261
 262 </div>
 263 <div class="section" id="description">
 264 <h2>DESCRIPTION<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
 265 <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
 266 (overflow and underflow are not detected). This gives you the ability to use
 267 memcached to generate shared sequences of values.</p>
 268 <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
 269 value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. The value is then returned via the
 270 uint32_t <code class="docutils literal notranslate"><span class="pre">value</span></code> pointer you pass to it.</p>
 271 <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
 272 value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. The value is then returned via the
 273 uint32_t <code class="docutils literal notranslate"><span class="pre">value</span></code> pointer you pass to it.</p>
 274 <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
 275 increments the value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. If the object specified by
 276 <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>
 277 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
 278 all other <code class="docutils literal notranslate"><span class="pre">expiration</span></code> values, the operation will succeed by seeding the value
 279 for that key with a initial value to expire with the provided expiration time.
 280 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
 281 <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
 282 available when using the binary protocol.</p>
 283 <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
 284 decrements the value by the <code class="docutils literal notranslate"><span class="pre">offset</span></code> passed to it. If the object specified by
 285 <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>
 286 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
 287 all other <code class="docutils literal notranslate"><span class="pre">expiration</span></code> values, the operation will succeed by seeding the value
 288 for that key with a initial value to expire with the provided expiration time.
 289 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
 290 <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
 291 available when using the binary protocol.</p>
 292 <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>,
 293 <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
 294 <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
 295 above.</p>
 296 </div>
 297 <div class="section" id="return-value">
 298 <h2>RETURN VALUE<a class="headerlink" href="#return-value" title="Permalink to this headline">¶</a></h2>
 299 <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.
 300 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>.
 301 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>
 302 </div>
 303 <div class="section" id="see-also">
 304 <h2>SEE ALSO<a class="headerlink" href="#see-also" title="Permalink to this headline">¶</a></h2>
 305 <ul class="simple">
 306 <li><p><em class="manpage"><a class="manpage reference external" href="https://linux.die.net/man/1/memcached">memcached(1)</a></em></p></li>
 307 <li><p><a class="reference internal" href="../libmemcached.html"><span class="doc">C/C++ Client Library for memcached</span></a></p></li>
 308 <li><p><a class="reference internal" href="memcached_strerror.html"><span class="doc">Converting Error Codes to Messages</span></a></p></li>
 309 </ul>
 310 </div>
 311 </div>
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