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                        Builtin Commands
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                        Special Commands
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                        Arrays
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                        Shell Metacharacters
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                        Expansions and Substitutions
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                        Brace Expansion
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                        Tilde Expansion
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                        Parameter Expansion
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                        Arithmetic Expansion
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                        Command Substitution
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                        Process Substitution
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                        Session and Process Group
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                        Process State Codes
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                        TTY
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                        Mutual Exclusion
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                        Redirections
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                        File Descriptors
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                        &lt;&lt; , &lt;&lt;&lt;
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                        Pipe
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                        Named Pipe
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                        Buffering
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                        Signals and Traps
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                            <b>11.1.</b>
                        
                        kill
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                        trap
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                        Signals Table
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                        Command Aliases
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                        Command History
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                            <b>14.</b>
                        
                        Command Completion
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                            <b>15.</b>
                        
                        Readline
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                            <b>16.</b>
                        
                        Colors and Prompt
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                            <b>17.</b>
                        
                        Locale
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                            <b>18.</b>
                        
                        sh
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                            <b>19.</b>
                        
                        Debugging
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                            <b>20.</b>
                        
                        Shell Variables
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                            <b>20.1.</b>
                        
                        Positional Parameters
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                            <b>20.2.</b>
                        
                        Special Parameters
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                            <b>21.</b>
                        
                        Shell Options
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                            <b>21.1.</b>
                        
                        Command-line options
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                            <b>22.</b>
                        
                        Tips
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                        <h2 id="arithmetic-expansion">Arithmetic Expansion</h2>
<p>Shell &#xC5D0;&#xC11C; &#xBA85;&#xB839;&#xBB38; &#xC791;&#xC131;&#xC2DC; &#xC0B0;&#xC220;&#xC5F0;&#xC0B0;&#xC774; &#xD544;&#xC694;&#xD560; &#xB54C; &#xC0AC;&#xC6A9;&#xD558;&#xB294; &#xD45C;&#xD604;&#xC2DD;&#xC785;&#xB2C8;&#xB2E4;.
&#xC0AC;&#xC6A9; &#xBC29;&#xC2DD;&#xC740; <code>(( ))</code> <a href="../special_commands.html">&#xD2B9;&#xC218;&#xBA85;&#xB839;</a> &#xACFC; &#xB3D9;&#xC77C;&#xD558;&#xC9C0;&#xB9CC;
&#xC774;&#xAC83;&#xC740; &#xAD04;&#xD638; &#xC55E;&#xC5D0; <code>$</code> &#xBB38;&#xC790;&#xAC00; &#xC788;&#xC5B4;&#xC11C; &#xBA85;&#xB839;&#xC73C;&#xB85C;&#xB294; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC5C6;&#xACE0;
<code>$( )</code> &#xBA85;&#xB839;&#xCE58;&#xD658;&#xACFC; &#xAC19;&#xC774; &#xC5F0;&#xC0B0; &#xACB0;&#xACFC;&#xB97C; &#xBCC0;&#xC218;&#xC5D0; &#xB300;&#xC785;&#xD558;&#xAC70;&#xB098; &#xBA85;&#xB839;&#xC758; &#xC778;&#xC218; &#xBD80;&#xBD84;&#xC5D0;&#xC11C; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.
&#xBA85;&#xB839;&#xCE58;&#xD658; &#xACFC;&#xB294; &#xB2EC;&#xB9AC; subshell &#xC774; &#xC544;&#xB2CC; &#xD604;&#xC7AC; shell &#xC5D0;&#xC11C; &#xC2E4;&#xD589;&#xB418;&#xBBC0;&#xB85C; &#xD604;&#xC7AC; shell &#xC758; &#xBCC0;&#xC218;&#xAC12;&#xC744;
&#xBCC0;&#xACBD;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xC2DD;&#xC744; &#xC791;&#xC131;&#xD560; &#xB54C;&#xB294; &#xB9E4;&#xAC1C;&#xBCC0;&#xC218; &#xD655;&#xC7A5;&#xACFC; &#xBA85;&#xB839; &#xCE58;&#xD658;&#xB3C4; &#xBAA8;&#xB450; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<blockquote>
<p>&#xAC19;&#xC740; &#xAE30;&#xB2A5;&#xC744; &#xD558;&#xB294; <code>$[  ]</code> &#xD45C;&#xD604;&#xC2DD;&#xC740; deprecated &#xB77C;&#xACE0; &#xD558;&#xB2C8; &#xC0AC;&#xC6A9;&#xD558;&#xC9C0; &#xB9D0;&#xC544;&#xC57C;&#xACA0;&#xC2B5;&#xB2C8;&#xB2E4;.<br>&#xC0B0;&#xC220;&#xC5F0;&#xC0B0;&#xC744; &#xD558;&#xB294; &#xC678;&#xBD80; &#xBA85;&#xB839;&#xC73C;&#xB85C;&#xB294; <code>expr</code>, <code>bc</code> &#xB4F1;&#xC774; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
</blockquote>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xC5F0;&#xC0B0; &#xACB0;&#xACFC;&#xAC12;&#xC744; &#xBCC0;&#xC218;&#xC5D0; &#xB300;&#xC785;&#xC2DC;&#xD0AC; &#xC218; &#xC788;&#xB2E4;.</span>
$ AA=$(( <span class="hljs-number">1</span> + <span class="hljs-number">2</span> )); <span class="hljs-built_in">echo</span> <span class="hljs-variable">$AA</span>
<span class="hljs-number">3</span>

$ CC=$(( BB = AA += <span class="hljs-number">2</span> ))

$ <span class="hljs-built_in">echo</span> <span class="hljs-variable">$AA</span> <span class="hljs-variable">$BB</span> <span class="hljs-variable">$CC</span>
<span class="hljs-number">5</span> <span class="hljs-number">5</span> <span class="hljs-number">5</span>

<span class="hljs-comment"># &#xBA85;&#xB839;&#xC758; &#xC778;&#xC218; &#xBD80;&#xBD84;&#xC5D0;&#xC11C; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xB2E4;.</span>
$ expr <span class="hljs-number">100</span> + $(( AA + <span class="hljs-number">2</span> ))
<span class="hljs-number">107</span>

<span class="hljs-comment"># &#xC2DD; &#xB0B4;&#xC5D0;&#xC11C;&#xB294; &#xB9E4;&#xAC1C;&#xBCC0;&#xC218; &#xD655;&#xC7A5;, &#xBA85;&#xB839; &#xCE58;&#xD658;&#xB3C4; &#xBAA8;&#xB450; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xB2E4;.</span>
$ B=<span class="hljs-number">1000</span>
$ <span class="hljs-built_in">echo</span> $(( B += `date | awk <span class="hljs-string">&apos;{print $4}&apos;</span>` ))
<span class="hljs-number">3020</span>
</code></pre>
<p>&#xD604;&#xC7AC; shell &#xC758; &#xBCC0;&#xC218;&#xAC12;&#xC744; &#xBCC0;&#xACBD;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ AA=<span class="hljs-number">100</span>

$ : $(( AA = <span class="hljs-number">200</span> ))

$ <span class="hljs-built_in">echo</span> <span class="hljs-variable">$AA</span>
<span class="hljs-number">200</span>
</code></pre>
<h4 id="&#xBA85;&#xB839;-&#xD65C;&#xC6A9;&#xD558;&#xAE30;"><code>:</code> &#xBA85;&#xB839; &#xD65C;&#xC6A9;&#xD558;&#xAE30;</h4>
<p><code>:</code> &#xBA85;&#xB839;&#xC744; &#xD65C;&#xC6A9;&#xD558;&#xBA74; <code>(( ))</code> &#xBA85;&#xB839;&#xACFC; &#xAC19;&#xC774; &#xB2E8;&#xB3C5;&#xC73C;&#xB85C; &#xC5F0;&#xC0B0;&#xC744; &#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xAE30;&#xBCF8;&#xC801;&#xC73C;&#xB85C; &#xBA85;&#xB839;&#xD589; &#xC0C1;&#xC5D0;&#xC11C; &#xB2E8;&#xB3C5;&#xC73C;&#xB85C; &#xC0AC;&#xC6A9;&#xD560; &#xC218;&#xB294; &#xC5C6;&#xB2E4;.</span>
$ $(( <span class="hljs-number">1</span> + <span class="hljs-number">2</span> ))
<span class="hljs-number">3</span>: <span class="hljs-built_in">command</span> not found

$ AA=$(( <span class="hljs-number">1</span> + <span class="hljs-number">2</span> ))

<span class="hljs-comment"># &#xD558;&#xC9C0;&#xB9CC; &apos;:&apos; &#xBA85;&#xB839;&#xC744; &#xD65C;&#xC6A9;&#xD558;&#xBA74; &#xBA85;&#xB839;&#xD589; &#xC0C1;&#xC5D0;&#xC11C; &#xB2E8;&#xB3C5;&#xC73C;&#xB85C; &#xC5F0;&#xC0B0;&#xC744; &#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</span>
$ : $(( AA += <span class="hljs-number">1</span>, BB = AA + <span class="hljs-number">1</span> ))

$ <span class="hljs-built_in">echo</span> <span class="hljs-variable">$AA</span> <span class="hljs-variable">$BB</span>
<span class="hljs-number">4</span> <span class="hljs-number">5</span>
</code></pre>
<h3 id="8-&#xC9C4;&#xC218;-16-&#xC9C4;&#xC218;-&#xC5F0;&#xC0B0;">8 &#xC9C4;&#xC218;, 16 &#xC9C4;&#xC218; &#xC5F0;&#xC0B0;</h3>
<p>&#xC22B;&#xC790;&#xAC00; <code>0</code> &#xC73C;&#xB85C; &#xC2DC;&#xC791;&#xD558;&#xBA74; 8 &#xC9C4;&#xC218;&#xB85C;, <code>0x</code> &#xB85C; &#xC2DC;&#xC791;&#xD558;&#xBA74; 16 &#xC9C4;&#xC218;&#xB85C; &#xC778;&#xC2DD;&#xD569;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ <span class="hljs-built_in">echo</span> $(( <span class="hljs-number">010</span> )) $(( <span class="hljs-number">8</span><span class="hljs-comment">#10 ))          # 8 &#xC9C4;&#xC218;</span>
<span class="hljs-number">8</span> <span class="hljs-number">8</span>

$ <span class="hljs-built_in">echo</span> $(( <span class="hljs-number">0</span>x10 )) $(( <span class="hljs-number">16</span><span class="hljs-comment">#10 ))        # 16 &#xC9C4;&#xC218;</span>
<span class="hljs-number">16</span> <span class="hljs-number">16</span>

$ <span class="hljs-built_in">echo</span> $(( <span class="hljs-number">2</span><span class="hljs-comment">#1010 ))                   # 2 &#xC9C4;&#xC218;</span>
<span class="hljs-number">10</span>

$ AA=<span class="hljs-number">032</span>; <span class="hljs-built_in">echo</span> $(( <span class="hljs-number">10</span><span class="hljs-comment">#$AA ))           # 10 &#xC9C4;&#xC218; ( 0 &#xC774; &#xC81C;&#xAC70;&#xB41C;&#xB2E4; )</span>
<span class="hljs-number">32</span>

$ <span class="hljs-built_in">echo</span> $(( <span class="hljs-number">010</span> + <span class="hljs-number">0</span>x10 + <span class="hljs-number">10</span> + <span class="hljs-number">2</span><span class="hljs-comment">#10 ))   # 8 &#xC9C4;&#xC218; + 16 &#xC9C4;&#xC218; + 10 &#xC9C4;&#xC218; + 2 &#xC9C4;&#xC218;</span>
<span class="hljs-number">36</span>
</code></pre>
<p>8 &#xC9C4;&#xC218;&#xB098; 16 &#xC9C4;&#xC218;&#xB85C; &#xBCC0;&#xACBD;&#xD558;&#xB824;&#xBA74; printf &#xBA85;&#xB839;&#xC744; &#xC0AC;&#xC6A9;&#xD558;&#xBA74; &#xB429;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ <span class="hljs-built_in">printf</span> %x $(( <span class="hljs-number">0135</span> ))           <span class="hljs-comment"># 8 &#xC9C4;&#xC218;&#xB97C; 16 &#xC9C4;&#xC218;&#xB85C; &#xBCC0;&#xACBD;</span>
<span class="hljs-number">5</span>d

$ <span class="hljs-built_in">printf</span> %o $(( <span class="hljs-number">0</span>x5d ))           <span class="hljs-comment"># 16 &#xC9C4;&#xC218;&#xB97C; 8 &#xC9C4;&#xC218;&#xB85C; &#xBCC0;&#xACBD;</span>
<span class="hljs-number">135</span>

$ <span class="hljs-built_in">printf</span> %x $(( <span class="hljs-number">2</span><span class="hljs-comment">#11010101 ))     # 2 &#xC9C4;&#xC218;&#xB97C; 16 &#xC9C4;&#xC218;&#xB85C; &#xBCC0;&#xACBD;</span>
d5
</code></pre>
<h3 id="bitwise-&#xC5F0;&#xC0B0;">Bitwise &#xC5F0;&#xC0B0;</h3>
<ul>
<li><strong>&gt;&gt;</strong>&#xA0;&#xA0;&#xA0;(Right Shift) - Shift bits to right and adds &apos;0&apos;s on left (Divide by 2 operation)</li>
<li><strong>&lt;&lt;</strong>&#xA0;&#xA0;&#xA0;(Left Shift) - Shifts bits to left and add &apos;0&apos; on right (Multiply by 2 operation)</li>
<li><strong>&amp;</strong>&#xA0;&#xA0;&#xA0;&#xA0;(Bitwise AND) - Performs AND operation on every bit and produces result</li>
<li><strong>|</strong>&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;(Bitwise OR) - Performs OR operation on every bit and produces result</li>
<li><strong>^</strong>&#xA0;&#xA0;&#xA0;&#xA0;(Bitwise XOR) - Performs XOR operation on every bit and produces result</li>
<li><strong>~</strong>&#xA0;&#xA0;&#xA0;&#xA0;(Bitwise NOT) - Inverts all the bits</li>
</ul>
<pre><code class="lang-bash"><span class="hljs-comment"># Right Shift</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> &gt;&gt; <span class="hljs-number">1</span> ))         <span class="hljs-comment"># &apos;1111&apos; &gt;&gt; 1 = &apos;0111&apos;  ( Ans : 7 )</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> &gt;&gt; <span class="hljs-number">3</span> ))         <span class="hljs-comment"># &apos;1111&apos; &gt;&gt; 3 = &apos;0001&apos;  ( Ans : 1 )</span>

<span class="hljs-comment"># Left Shift</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> &lt;&lt; <span class="hljs-number">1</span> ))         <span class="hljs-comment"># &apos;1111&apos; &lt;&lt; 1 = &apos;11110&apos;  ( Ans : 30 )</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> &lt;&lt; <span class="hljs-number">3</span> ))         <span class="hljs-comment"># &apos;1111&apos; &lt;&lt; 3 = &apos;1111000&apos;  ( Ans : 120 )</span>

<span class="hljs-comment"># Bitwise AND</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> &amp; <span class="hljs-number">1</span> ))          <span class="hljs-comment"># &apos;1111&apos; &amp; &apos;0001&apos; = &apos;0001&apos;  ( Ans : 1 )</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> &amp; <span class="hljs-number">3</span> ))          <span class="hljs-comment"># &apos;1111&apos; &amp; &apos;0011&apos; = &apos;0011&apos;  ( Ans : 3 )</span>

<span class="hljs-comment"># Bitwise OR</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> | <span class="hljs-number">1</span> ))          <span class="hljs-comment"># &apos;1111&apos; | &apos;0001&apos; = &apos;1111&apos;  ( Ans : 15 )</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> | <span class="hljs-number">3</span> ))          <span class="hljs-comment"># &apos;1111&apos; | &apos;0011&apos; = &apos;1111&apos;  ( Ans : 15 )</span>

<span class="hljs-comment"># Bitwise XOR</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> ^ <span class="hljs-number">1</span> ))          <span class="hljs-comment"># &apos;1111&apos; ^ &apos;0001&apos; = &apos;1110&apos;  ( Ans : 14 )</span>
<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">15</span> ^ <span class="hljs-number">3</span> ))          <span class="hljs-comment"># &apos;1111&apos; ^ &apos;0011&apos; = &apos;1100&apos;  ( Ans : 12 )</span>

<span class="hljs-comment"># Bitwise NOT</span>
<span class="hljs-built_in">echo</span> $(( ~<span class="hljs-number">1</span> ))              <span class="hljs-comment"># ~ &apos;0000 0001&apos; = &apos;1111 1110&apos;  ( Ans : -2 )</span>
<span class="hljs-built_in">echo</span> $(( ~<span class="hljs-number">3</span> ))              <span class="hljs-comment"># ~ &apos;0000 0011&apos; = &apos;1111 1100&apos;  ( Ans : -4 )</span>
<span class="hljs-built_in">echo</span> $(( ~<span class="hljs-number">15</span> ))             <span class="hljs-comment"># ~ &apos;0000 1111&apos; = &apos;1111 0000&apos;  ( Ans : -16 )</span>
</code></pre>
<p>&#xC5F0;&#xC0B0;&#xC790; &#xC6B0;&#xC120;&#xC21C;&#xC704;&#xB294; C &#xC5B8;&#xC5B4;&#xC640; &#xAC19;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<h5 id="-shift-&#xC5F0;&#xC0B0;------------------"><code>~</code> &gt; <code>shift &#xC5F0;&#xC0B0;</code> &gt; <code>&lt;, &lt;=, &gt;, &gt;=</code> &gt; <code>==, !=</code> &gt; <code>&amp;</code> &gt; <code>^</code> &gt; <code>|</code> &gt; <code>&amp;&amp;</code> &gt; <code>||</code></h5>
<pre><code class="lang-bash"><span class="hljs-comment"># shift &#xC5F0;&#xC0B0;&#xC774; &#xC6B0;&#xC120;&#xC21C;&#xC704;&#xAC00; &#xB192;&#xAE30; &#xB54C;&#xBB38;&#xC5D0; &#xC774;&#xAC83;&#xC740; 2 | ( 4 &gt;&gt; 1 ) &#xC640; &#xAC19;&#xB2E4;.</span>
$ <span class="hljs-built_in">echo</span> $(( <span class="hljs-number">2</span> | <span class="hljs-number">4</span> &gt;&gt; <span class="hljs-number">1</span> ))
<span class="hljs-number">2</span>

$ <span class="hljs-built_in">echo</span> $(( ( <span class="hljs-number">2</span> | <span class="hljs-number">4</span> ) &gt;&gt; <span class="hljs-number">1</span> ))
<span class="hljs-number">3</span>

<span class="hljs-comment"># &amp;, ^, | &#xC5F0;&#xC0B0;&#xC740; ==, != &#xB4F1;&#xD638; &#xBCF4;&#xB2E4;&#xB3C4; &#xC6B0;&#xC120;&#xC21C;&#xC704;&#xAC00; &#xB0AE;&#xB2E4;.</span>
<span class="hljs-comment"># &#xB530;&#xB77C;&#xC11C; &#xB2E4;&#xC74C; &#xC2DD;&#xC740; 2 | ( 4 == 3 ) &#xC640; &#xAC19;&#xB2E4;.</span>
$ <span class="hljs-built_in">echo</span> $(( <span class="hljs-number">2</span> | <span class="hljs-number">4</span> == <span class="hljs-number">3</span> ))
<span class="hljs-number">2</span>

$ <span class="hljs-built_in">echo</span> $(( ( <span class="hljs-number">2</span> | <span class="hljs-number">4</span> ) == <span class="hljs-number">3</span> ))
<span class="hljs-number">0</span>
</code></pre>
<blockquote>
<p><code>^</code> &#xB294; XOR &#xC5F0;&#xC0B0;&#xC790;&#xB85C; &#xC0AC;&#xC6A9;&#xB418;&#xBBC0;&#xB85C; &#xAC70;&#xB4ED;&#xC81C;&#xACF1; &#xC5F0;&#xC0B0;&#xC790;&#xB294; <code>**</code> &#xB97C; &#xC0AC;&#xC6A9;&#xD569;&#xB2C8;&#xB2E4;.</p>
</blockquote>

                    
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