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POCan someone explain redis setbit command?
 

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  1. POCan someone explain redis setbit command?
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    <pre><code>&gt; setbit mykey 1 1 &gt; setbit mykey 7 1 </code></pre> <p>When I store string value 1 and 7 into "mykey", <strong>what was exactly stored in redis</strong>? And how the getbit works inside redis?</p> <p><strong>Does anyone try to loop the bit inside this value?</strong> I know bitcount will give me number 2, but I also want to get the exact string value 1 and 7 from it, is it possible?</p> <p>--</p> <p>I doing some experiment by using erlang redis client to read the output.</p> <pre><code>&gt; setbit mykey 1 1 </code></pre> <p>erlang output:</p> <pre><code>&lt;&lt;"@"&gt;&gt; </code></pre> <p>Then I delete this entry:</p> <pre><code>&gt; del mykey </code></pre> <p>I do the same thing to offset 2 4 8, here you can see the mapping:</p> <pre><code>When offset is 1, the output is &lt;&lt;"@"&gt;&gt;; When offset is 2, the output is &lt;&lt;" "&gt;&gt;; When offset is 4, the output is &lt;&lt;"\b"&gt;&gt;; When offset is 8, the output is &lt;&lt;0,128&gt;&gt;; </code></pre> <p>Honestly, I am more confused now.</p> <p>Or someone can explain this <a href="https://github.com/antirez/redis/blob/ec7f480e11e1b697c05ac40d69a6a9fca88fc439/src/bitops.c" rel="nofollow">"bitops.c"</a></p> <p>-- updates ---</p> <p>Maybe I should mention the reason why I want to do this to make the question more clear. We all know it will be cool to use bitmap to store online users. What I am trying to do is get the exactly user id who is online from what redis stored.</p> <p><strong>Just finished a <a href="https://github.com/JoshuaChi/extract-offsets-from-redis-bitmap" rel="nofollow">quick version</a> to extract offsets from redis. Please feel free to improve it.</strong></p>
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    1. COe.g. if I do "get mykey", I get "A\X80", what's this?
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