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                        Interactive vs Non-Interactive Shell
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                        etc
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                            <b>3.</b>
                        
                        Test
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                            <b>3.1.</b>
                        
                        Operators
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                            <b>4.</b>
                        
                        Subshells
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                        Process Creation
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                            <b>5.</b>
                        
                        Commands
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                            <b>5.1.</b>
                        
                        Builtin Commands
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                            <b>5.1.1.</b>
                        
                        read
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                            <b>5.1.2.</b>
                        
                        printf
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                            <b>5.1.3.</b>
                        
                        eval
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                            <b>5.1.4.</b>
                        
                        getopts
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                            <b>5.2.</b>
                        
                        Keyword Commands
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                        Compound Commands
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                        Special Commands
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                        expr
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                        grep
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                        find
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                        xargs
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                            <b>6.</b>
                        
                        Arrays
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                            <b>7.</b>
                        
                        Shell Metacharacters
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                            <b>7.1.</b>
                        
                        Precedence
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                            <b>8.</b>
                        
                        Expansions and Substitutions
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                            <b>8.1.</b>
                        
                        Brace Expansion
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                            <b>8.2.</b>
                        
                        Tilde Expansion
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                            <b>8.3.</b>
                        
                        Parameter Expansion
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                            <b>8.4.</b>
                        
                        Arithmetic Expansion
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                            <b>8.5.</b>
                        
                        Command Substitution
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                            <b>8.6.</b>
                        
                        Process Substitution
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                            <b>8.7.</b>
                        
                        Word Splitting
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                            <b>8.8.</b>
                        
                        Filename Expansion
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                            <b>9.</b>
                        
                        Job Control
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                            <b>9.1.</b>
                        
                        Session and Process Group
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                            <b>9.2.</b>
                        
                        Process State Codes
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                            <b>9.3.</b>
                        
                        TTY
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                            <b>9.4.</b>
                        
                        Mutual Exclusion
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                            <b>10.</b>
                        
                        Redirections
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                            <b>10.1.</b>
                        
                        File Descriptors
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                            <b>10.2.</b>
                        
                        &lt;&lt; , &lt;&lt;&lt;
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                            <b>10.3.</b>
                        
                        Pipe
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                            <b>10.4.</b>
                        
                        Named Pipe
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                            <b>10.5.</b>
                        
                        Buffering
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                            <b>11.</b>
                        
                        Signals and Traps
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                            <b>11.1.</b>
                        
                        kill
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                            <b>11.2.</b>
                        
                        trap
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                            <b>11.3.</b>
                        
                        Signals Table
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                            <b>12.</b>
                        
                        Command Aliases
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                            <b>13.</b>
                        
                        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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        <li class="chapter " data-level="17" data-path="shell_variables.html">
            
                
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                            <b>17.</b>
                        
                        Shell Variables
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                            <b>17.1.</b>
                        
                        Positional Parameters
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                            <b>17.2.</b>
                        
                        Special Parameters
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        <li class="chapter " data-level="18" data-path="shell_options.html">
            
                
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                            <b>18.</b>
                        
                        Shell Options
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                            <b>18.1.</b>
                        
                        Command-line options
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                            <b>19.</b>
                        
                        Debugging
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                            <b>20.</b>
                        
                        Locale
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                            <b>21.</b>
                        
                        sh
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                            <b>22.</b>
                        
                        Tips
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                            <b>23.</b>
                        
                        맺음말
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                            <b>24.</b>
                        
                        별책부록
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                    <section class="normal" id="section-">
                    
                        <h2 id="keyword-commands">Keyword Commands</h2>
<p>&#xB2E4;&#xC74C;&#xC740; shell &#xC5D0;&#xC11C; &#xC81C;&#xACF5;&#xD558;&#xB294; &#xD0A4;&#xC6CC;&#xB4DC;&#xB4E4; &#xC785;&#xB2C8;&#xB2E4;.
&#xB300;&#xBD80;&#xBD84; <a href="compound_commands.html">compound commands</a> &#xB97C; &#xC791;&#xC131;&#xD558;&#xB294;&#xB370; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ compgen -k | column

<span class="hljs-keyword">if</span>        <span class="hljs-keyword">then</span>      <span class="hljs-keyword">else</span>      <span class="hljs-keyword">elif</span>      <span class="hljs-keyword">fi</span>        <span class="hljs-keyword">case</span>      
<span class="hljs-keyword">esac</span>      <span class="hljs-keyword">for</span>       select    <span class="hljs-keyword">while</span>     until     <span class="hljs-keyword">do</span>        
<span class="hljs-keyword">done</span>      <span class="hljs-keyword">in</span>        <span class="hljs-keyword">function</span>  time      {         }         
!         [[        ]]        coproc
</code></pre>
<p>&#xAE30;&#xBCF8;&#xC801;&#xC73C;&#xB85C; &#xBA85;&#xB839; &#xC774;&#xB984;&#xC774; &#xC704;&#xCE58;&#xD558;&#xB294; &#xACF3;&#xC5D0;&#xC11C; &#xC0AC;&#xC6A9;&#xB418;&#xACE0; &#xBA85;&#xB839;&#xC758; &#xC778;&#xC218; &#xBD80;&#xBD84;&#xC5D0;&#xC11C;&#xB294; 
&#xC0AC;&#xC6A9;&#xB420; &#xC218; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xAE30;&#xBCF8;&#xC801;&#xC73C;&#xB85C; &#xBA85;&#xB839; &#xC774;&#xB984;&#xC774; &#xC704;&#xCE58;&#xD558;&#xB294; &#xACF3;&#xC5D0;&#xC11C; &#xC0AC;&#xC6A9;&#xB41C;&#xB2E4;.</span>
$ <span class="hljs-keyword">if</span> [ <span class="hljs-number">1</span> = <span class="hljs-number">1</span> ]; <span class="hljs-keyword">then</span> <span class="hljs-built_in">echo</span> yes; <span class="hljs-keyword">fi</span>
yes

<span class="hljs-comment"># &#xBA85;&#xB839;&#xC758; &#xC778;&#xC218; &#xBD80;&#xBD84;&#xC5D0;&#xC11C;&#xB294; &#xC0AC;&#xC6A9;&#xB420; &#xC218; &#xC5C6;&#xB2E4;.</span>
<span class="hljs-comment"># &#xB2E4;&#xC74C;&#xC740; if &#xBB38;&#xC774; shell &#xC5D0;&#xC758;&#xD574; &#xCC98;&#xB9AC;&#xB418;&#xB294; &#xAC83;&#xC774; &#xC544;&#xB2C8;&#xACE0; sudo &#xBA85;&#xB839;&#xC758; &#xC778;&#xC218;&#xB85C; &#xC804;&#xB2EC;&#xB418;&#xC5B4; &#xCC98;&#xB9AC;&#xB418;&#xBBC0;&#xB85C; &#xC624;&#xB958;.</span>
<span class="hljs-comment"># ( sudo &#xBA85;&#xB839;&#xC774; &#xC2E4;&#xD589;&#xD560; if &#xB77C;&#xB294; &#xC678;&#xBD80; &#xBA85;&#xB839;&#xC740; &#xC874;&#xC7AC;&#xD558;&#xC9C0; &#xC54A;&#xB294;&#xB2E4;. )</span>
$ sudo <span class="hljs-keyword">if</span> [ <span class="hljs-number">1</span> = <span class="hljs-number">1</span> ]; <span class="hljs-keyword">then</span> <span class="hljs-built_in">echo</span> yes; <span class="hljs-keyword">fi</span>
bash: syntax error near unexpected token <span class="hljs-string">&apos;then&apos;</span>

<span class="hljs-comment"># &#xB2E4;&#xC74C;&#xC740; &apos;sh -c ...&apos; &#xBA85;&#xB839;&#xBB38;&#xC774; sudo &#xC5D0; &#xC804;&#xB2EC;&#xB418;&#xC5B4; &#xC2E4;&#xD589;&#xB418;&#xACE0; if &#xBB38;&#xC740; &apos;sh -c&apos; &#xC5D0;&#xC758;&#xD574; &#xC2E4;&#xD589;&#xB41C;&#xB2E4;.</span>
$ sudo sh -c <span class="hljs-string">&apos;if [ 1 = 1 ]; then echo yes; fi&apos;</span>
yes

$ { <span class="hljs-built_in">echo</span> hello; <span class="hljs-built_in">echo</span> world ;} &gt; file 
$ OK

<span class="hljs-comment"># &#xB9C8;&#xCC2C;&#xAC00;&#xC9C0;&#xB85C; sudo &#xBA85;&#xB839;&#xC774; &#xC2E4;&#xD589;&#xD560; &apos;{&apos; &#xB77C;&#xB294; &#xC678;&#xBD80; &#xBA85;&#xB839;&#xC740; &#xC874;&#xC7AC;&#xD558;&#xC9C0; &#xC54A;&#xB294;&#xB2E4;.</span>
$ sudo { <span class="hljs-built_in">echo</span> hello; <span class="hljs-built_in">echo</span> world ;} &gt; file 
bash: syntax error near unexpected token <span class="hljs-string">&apos;}&apos;</span>

$ sudo sh -c <span class="hljs-string">&apos;{ echo hello; echo world ;} &gt; file&apos;</span>
$ OK
</code></pre>
<p><code>!</code> &#xD0A4;&#xC6CC;&#xB4DC;&#xB294; &#xBA85;&#xB839; &#xC55E;&#xC5D0; &#xB450;&#xC5B4; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xBC18;&#xC804; &#xC2DC;&#xD0AC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ [ <span class="hljs-number">1</span> = <span class="hljs-number">2</span> ] &amp;&amp; <span class="hljs-built_in">echo</span> yes

$ ! [ <span class="hljs-number">1</span> = <span class="hljs-number">2</span> ] &amp;&amp; <span class="hljs-built_in">echo</span> yes
yes

$ date -@ &amp;&amp; <span class="hljs-built_in">echo</span> yes....
date: invalid option -- <span class="hljs-string">&apos;@&apos;</span>
Try <span class="hljs-string">&apos;date --help&apos;</span> <span class="hljs-keyword">for</span> more information.

$ ! date -@ &amp;&amp; <span class="hljs-built_in">echo</span> yes....
date: invalid option -- <span class="hljs-string">&apos;@&apos;</span>
Try <span class="hljs-string">&apos;date --help&apos;</span> <span class="hljs-keyword">for</span> more information.
yes....   <span class="hljs-comment"># &lt;----- yes</span>
</code></pre>
<p>&#xC5EC;&#xAE30;&#xC5D0;&#xC11C;&#xB294; <code>time</code>, <code>coproc</code> &#xD0A4;&#xC6CC;&#xB4DC;&#xC5D0; &#xB300;&#xD574;&#xC11C;&#xB9CC; &#xC54C;&#xC544;&#xBCF4;&#xACE0; &#xB098;&#xBA38;&#xC9C0;&#xB294; compound commands &#xBA54;&#xB274;&#xC5D0;&#xC11C;
&#xB2E4;&#xB8E8;&#xACA0;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<h3 id="time">time</h3>
<blockquote>
<p>time [-p] pipeline</p>
</blockquote>
<p>&#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD558;&#xB294;&#xB370; &#xAC78;&#xB9B0; &#xC2DC;&#xAC04;&#xC744; &#xD45C;&#xC2DC;&#xD574;&#xC90D;&#xB2C8;&#xB2E4;. &#xBA85;&#xB839;&#xB4E4;&#xC774; &#xD30C;&#xC774;&#xD504;&#xB85C; &#xC5F0;&#xACB0;&#xB418;&#xAC70;&#xB098; <code>{ }</code>, <code>( )</code> &#xB85C; group &#xB418;&#xC5B4;&#xC788;&#xC744; &#xACBD;&#xC6B0; &#xBAA8;&#xB4E0; &#xBA85;&#xB839;&#xB4E4;&#xC744; &#xD3EC;&#xD568;&#xD569;&#xB2C8;&#xB2E4;. TIMEFORMAT &#xD658;&#xACBD;&#xBCC0;&#xC218;&#xB97C; &#xC774;&#xC6A9;&#xD574; &#xCD9C;&#xB825; &#xD3EC;&#xBA67;&#xC744; &#xBCC0;&#xACBD;&#xD560;&#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;. </p>
<ul>
<li>real</li>
</ul>
<p>wall clock &#xC2DC;&#xAC04;&#xC774;&#xB77C;&#xACE0; &#xD558;&#xBA70; &#xD504;&#xB85C;&#xADF8;&#xB7A8;&#xC774; &#xC2DC;&#xC791;&#xB41C; &#xD6C4;&#xBD80;&#xD130; &#xC885;&#xB8CC;&#xB420; &#xB54C;&#xAE4C;&#xC9C0;&#xB97C; &#xC2DC;&#xACC4;&#xB85C; &#xC7B0;&#xAC83;&#xACFC; &#xAC19;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xADF8;&#xB7EC;&#xBBC0;&#xB85C; &#xD504;&#xB85C;&#xADF8;&#xB7A8; &#xC2E4;&#xD589;&#xC2DC; &#xB2E8;&#xC21C;&#xD788; I/O &#xB97C; &#xC704;&#xD574; wait &#xD55C; &#xC2DC;&#xAC04;&#xC774;&#xB098; sleep &#xD55C; &#xC2DC;&#xAC04;&#xB3C4; &#xBAA8;&#xB450; &#xD3EC;&#xD568;&#xB429;&#xB2C8;&#xB2E4;. </p>
<pre><code class="lang-bash">$ time { sleep <span class="hljs-number">1</span>; sleep <span class="hljs-number">2</span> ;}

real    <span class="hljs-number">0</span>m3.<span class="hljs-number">002</span>s
user    <span class="hljs-number">0</span>m0.<span class="hljs-number">000</span>s
sys     <span class="hljs-number">0</span>m0.<span class="hljs-number">000</span>s
</code></pre>
<ul>
<li>user</li>
</ul>
<p>user &#xBAA8;&#xB4DC;&#xC5D0;&#xC11C; &#xC0AC;&#xC6A9;&#xD55C; cpu &#xC2DC;&#xAC04;&#xC785;&#xB2C8;&#xB2E4;. wait &#xD55C; &#xC2DC;&#xAC04;&#xC740; &#xD3EC;&#xD568;&#xB418;&#xC9C0; &#xC54A;&#xC2B5;&#xB2C8;&#xB2E4;.
<code>user + sys</code> &#xC2DC;&#xAC04;&#xC774; &#xC2E4;&#xC9C8;&#xC801;&#xC73C;&#xB85C; &#xD504;&#xB85C;&#xADF8;&#xB7A8;&#xC774; &#xC0AC;&#xC6A9;&#xD55C; cpu &#xC2DC;&#xAC04;&#xC774;&#xB77C;&#xACE0; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<ul>
<li>sys</li>
</ul>
<p>kernel &#xBAA8;&#xB4DC;&#xC5D0;&#xC11C; &#xC0AC;&#xC6A9;&#xD55C; cpu &#xC2DC;&#xAC04;&#xC785;&#xB2C8;&#xB2E4;. &#xBA54;&#xBAA8;&#xB9AC;&#xB97C; &#xD560;&#xB2F9;&#xD558;&#xAC70;&#xB098;, &#xB514;&#xC2A4;&#xD06C; &#xAC19;&#xC740; &#xC7A5;&#xCE58;&#xC5D0; &#xC811;&#xADFC;&#xD558;&#xB294; &#xAC83;&#xC740; system call &#xC744; &#xD1B5;&#xD574;&#xC11C; kernel &#xBAA8;&#xB4DC;&#xC5D0;&#xC11C; &#xC2E4;&#xD589;&#xB429;&#xB2C8;&#xB2E4;. </p>
<h5 id="real-&#x2260;-user--sys">real &#x2260; user + sys</h5>
<p>&#xC694;&#xC998;&#xC740; &#xB300;&#xBD80;&#xBD84; multi-core cpu &#xB97C; &#xC0AC;&#xC6A9;&#xD569;&#xB2C8;&#xB2E4;. 
&#xADF8;&#xB798;&#xC11C; &#xAC00;&#xB839; 2 core cpu &#xB97C; &#xC0AC;&#xC6A9; &#xC911;&#xC774;&#xB77C;&#xACE0; &#xAC00;&#xC815;&#xD588;&#xC744;&#xB54C;,  &#xD504;&#xB85C;&#xADF8;&#xB7A8;&#xC774; &#xC2E4;&#xD589;&#xD6C4; &#xC885;&#xB8CC;&#xB420;&#xB54C;&#xAE4C;&#xC9C0; 1&#xBD84;&#xC774; &#xAC78;&#xB838;&#xACE0;, &#xAC01; core &#xC5D0;&#xC11C; 1&#xBD84;&#xC758; cpu &#xC2DC;&#xAC04;&#xC744; &#xC0AC;&#xC6A9;&#xD588;&#xB2E4;&#xBA74;  <code>real</code> &#xC740; 1&#xBD84;&#xC774;&#xC9C0;&#xB9CC; <code>user + sys</code> &#xB294; 2 &#xBD84;&#xC774; &#xB420;&#xC218;&#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.   </p>
<pre><code class="lang-bash">real    <span class="hljs-number">1</span>m47.<span class="hljs-number">363</span>s
user    <span class="hljs-number">2</span>m41.<span class="hljs-number">318</span>s
sys     <span class="hljs-number">0</span>m4.<span class="hljs-number">013</span>s
</code></pre>
<h5 id="exit-status">Exit Status:</h5>
<p>&#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC740; pipeline &#xC758; &#xB9AC;&#xD134;&#xAC12;&#xC774; &#xB429;&#xB2C8;&#xB2E4;.</p>
<p><a name="coproc"></a></p>
<h3 id="coproc">coproc</h3>
<blockquote>
<p>coproc [NAME] command [redirections]</p>
</blockquote>
<p>coproc (coprocess) &#xB294; &#xB450; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xAC04;&#xC5D0; &#xC591;&#xBC29;&#xD5A5; &#xD1B5;&#xC2E0;&#xC744; &#xAC00;&#xB2A5;&#xD558;&#xAC8C; &#xD569;&#xB2C8;&#xB2E4;.
coproc &#xB294; <em>command</em> &#xB97C; background &#xB85C; &#xC2E4;&#xD589;&#xC2DC;&#xD0A4;&#xB294;&#xB370; &#xC774;&#xB54C; <em>command</em> &#xC758; stdin, stdout &#xC774;
&#xD30C;&#xC774;&#xD504;&#xB97C; &#xD1B5;&#xD574; &#xD604;&#xC7AC; shell &#xC758; FD &#xC640; &#xC5F0;&#xACB0;&#xC774; &#xB429;&#xB2C8;&#xB2E4;.
&#xB530;&#xB77C;&#xC11C; &#xD604;&#xC7AC; shell &#xC5D0;&#xC11C; <em>command</em> &#xC5D0; &#xB370;&#xC774;&#xD130;&#xB97C; &#xBCF4;&#xB0B4;&#xACE0; &#xACB0;&#xACFC;&#xB97C; &#xBC1B;&#xC744; &#xC218; &#xC788;&#xAC8C; &#xB429;&#xB2C8;&#xB2E4;.
&#xD604;&#xC7AC; shell &#xC5D0; &#xC124;&#xC815;&#xB418;&#xB294; FD &#xB294; <code>$COPROC</code>  array &#xBCC0;&#xC218;&#xC5D0; &#xC800;&#xC7A5;&#xB418;&#xB294;&#xB370; <em>command</em> &#xB85C; &#xB370;&#xC774;&#xD130;&#xB97C;
&#xBCF4;&#xB0BC; &#xB54C;&#xB294; <code>&gt;&amp; ${COPROC[1]}</code> , &#xBC1B;&#xC744; &#xB54C;&#xB294; <code>&lt;&amp; ${COPROC[0]}</code> &#xC774; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.
background PID &#xB294; <code>$COPROC_PID</code> &#xBCC0;&#xC218;&#xC5D0; &#xC800;&#xC7A5;&#xB429;&#xB2C8;&#xB2E4;.</p>
<blockquote>
<p>coproc &#xBA85;&#xB839;&#xC5D0; <code>NAME</code> &#xC778;&#xC218;&#xAC00; &#xC0AC;&#xC6A9;&#xB418;&#xBA74; <code>$COPROC</code> &#xBCC0;&#xC218; &#xB300;&#xC2E0;&#xC5D0; <code>$NAME</code> &#xBCC0;&#xC218;&#xAC00; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.</p>
</blockquote>
<pre><code class="lang-bash"><span class="hljs-comment"># background &#xB85C; &#xC2E4;&#xD589;&#xB428;</span>
$ coproc  <span class="hljs-keyword">while</span> <span class="hljs-built_in">read</span> -r line; <span class="hljs-keyword">do</span> <span class="hljs-built_in">eval</span> expr <span class="hljs-string">&quot;<span class="hljs-variable">$line</span>&quot;</span>; <span class="hljs-keyword">done</span>
[<span class="hljs-number">1</span>] <span class="hljs-number">18008</span>

$ <span class="hljs-built_in">echo</span> <span class="hljs-string">&quot;1 + 2&quot;</span> &gt;&amp; <span class="hljs-variable">${COPROC[1]}</span>

$ <span class="hljs-built_in">read</span> -r &lt;&amp; <span class="hljs-variable">${COPROC[0]}</span>          <span class="hljs-comment"># &#xB610;&#xB294; read -r -u ${COPROC[0]}</span>

$ <span class="hljs-built_in">echo</span> <span class="hljs-variable">$REPLY</span>
<span class="hljs-number">3</span>

$ <span class="hljs-built_in">kill</span> <span class="hljs-variable">$COPROC_PID</span>
</code></pre>
<p>&#xC704;&#xC758; &#xBA85;&#xB839;&#xC740; &#xB2E4;&#xC74C;&#xACFC; &#xB3D9;&#xC77C;&#xD558;&#xB2E4;&#xACE0; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;. &#xADF8;&#xB7EC;&#xB2C8;&#xAE4C; coproc &#xB294; &#xD30C;&#xC774;&#xD504;&#xB97C; &#xC0DD;&#xC131;&#xD574;&#xC11C; FD &#xB97C; &#xC5F0;&#xACB0;&#xD558;&#xACE0; &#xC0AD;&#xC81C;&#xD558;&#xB294; &#xC791;&#xC5C5;&#xC744; &#xC790;&#xB3D9;&#xC73C;&#xB85C; &#xD574;&#xC900;&#xB2E4;&#xACE0; &#xBCF4;&#xBA74; &#xB418;&#xACA0;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ mkfifo inpipe outpipe &amp;&amp; <span class="hljs-built_in">exec</span> <span class="hljs-number">3</span>&lt;&gt;inpipe <span class="hljs-number">4</span>&lt;&gt;outpipe &amp;&amp; rm <span class="hljs-operator">-f</span> inpipe outpipe

$ <span class="hljs-keyword">while</span> <span class="hljs-built_in">read</span> -r line; <span class="hljs-keyword">do</span> <span class="hljs-built_in">eval</span> expr <span class="hljs-string">&quot;<span class="hljs-variable">$line</span>&quot;</span> &gt;&amp;<span class="hljs-number">3</span> ; <span class="hljs-keyword">done</span> &lt;&amp;<span class="hljs-number">4</span>  &amp;
[<span class="hljs-number">1</span>] <span class="hljs-number">17647</span>

$ <span class="hljs-built_in">echo</span> <span class="hljs-string">&quot;1 + 2&quot;</span> &gt;&amp;<span class="hljs-number">4</span>

$ <span class="hljs-built_in">read</span> -r &lt;&amp;<span class="hljs-number">3</span>

$ <span class="hljs-built_in">echo</span> <span class="hljs-variable">$REPLY</span>
<span class="hljs-number">3</span>

$ <span class="hljs-built_in">exec</span> <span class="hljs-number">3</span>&gt;&amp;- <span class="hljs-number">4</span>&gt;&amp;-

$ <span class="hljs-built_in">kill</span> <span class="hljs-number">17647</span>
</code></pre>
<p>&#xB2E4;&#xC74C;&#xC740; coproc &#xB97C; &#xC2E4;&#xD589;&#xD588;&#xC744; &#xB54C;&#xC758; FD &#xC0C1;&#xD0DC;&#xC778;&#xB370;&#xC694;.
while &#xBB38;&#xC744; &#xC2E4;&#xD589;&#xD558;&#xB294; background &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; stdin, stdout &#xC774;
pipe &#xB97C; &#xD1B5;&#xD574; &#xD604;&#xC7AC; shell &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; <code>${COPROC[0]}</code>, <code>${COPROC[1]}</code>
FD &#xC640; &#xC5F0;&#xACB0;&#xB418;&#xB294; &#xAC83;&#xC744; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<p><img src="images/coproc.png" alt="coproc"></p>
<blockquote>
<p>coproc &#xC5D0; &#xC758;&#xD574; &#xC0DD;&#xC131;&#xB418;&#xB294; FD &#xB294; &#xBA85;&#xB839; &#xCE58;&#xD658;, &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xCE58;&#xD658;&#xC5D0;&#xC11C;&#xB294; &#xC0AC;&#xC6A9;&#xC774; &#xAC00;&#xB2A5;&#xD558;&#xC9C0;&#xB9CC;
subshell &#xC774;&#xB098; background &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC5D0;&#xC11C;&#xB294; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;. deadlock &#xC744; &#xBC29;&#xC9C0;&#xD558;&#xAE30; 
&#xC704;&#xD574; coproc &#xC758; FD &#xB97C; close &#xD55C;&#xB2E4;&#xACE0; &#xD569;&#xB2C8;&#xB2E4;.</p>
</blockquote>
<h3 id="coproc-&#xB97C;-&#xC774;&#xC6A9;&#xD55C;-server-&#xC640;-client">coproc &#xB97C; &#xC774;&#xC6A9;&#xD55C; server &#xC640; client</h3>
<p>&#xB2E4;&#xC74C;&#xC740; unix domain socket &#xC744; &#xC774;&#xC6A9;&#xD558;&#xB294; server &#xC640; client &#xB97C; &#xB9CC;&#xB4DC;&#xB294; &#xC608;&#xC785;&#xB2C8;&#xB2E4;.
client &#xAC00; &#xC804;&#xB2EC;&#xD55C; &#xBA54;&#xC2DC;&#xC9C0;&#xC5D0; pong &#xC744; &#xCD94;&#xAC00;&#xD558;&#xC5EC; server &#xAC00; &#xC751;&#xB2F5;&#xD569;&#xB2C8;&#xB2E4;.
( internet domain socket &#xC73C;&#xB85C;&#xB3C4; &#xBCC0;&#xACBD;&#xD574; &#xBCF4;&#xC138;&#xC694; )</p>
<pre><code class="lang-bash">$ cat server.sh 
<span class="hljs-comment">#!/bin/bash -e</span>

SOCKET=server.sock
PIDFILE=server.pid

(
    <span class="hljs-built_in">exec</span> &lt; /dev/null                     <span class="hljs-comment"># &#xC11C;&#xBC84;&#xB97C; &#xB370;&#xBAAC;&#xC73C;&#xB85C; &#xC2E4;&#xD589;&#xD558;&#xAE30; &#xC704;&#xD574;</span>
    <span class="hljs-built_in">exec</span> &gt; /dev/null                     <span class="hljs-comment"># &#xD130;&#xBBF8;&#xB110;&#xB85C; &#xC5F0;&#xACB0;&#xB41C; standard streams &#xC744;</span>
    <span class="hljs-built_in">exec</span> <span class="hljs-number">2</span>&gt; /dev/null                    <span class="hljs-comment"># &#xBAA8;&#xB450; /dev/null &#xB85C; redirect &#xD569;&#xB2C8;&#xB2E4;.</span>

    coproc SERVER {                      <span class="hljs-comment"># coproc &#xAC00; &#xC2E4;&#xD589;&#xB418;&#xBA74; &#xBA3C;&#xC800; subshell &#xC774; &#xC0DD;&#xC131;&#xB418;&#xACE0;</span>
        <span class="hljs-built_in">exec</span> nc <span class="hljs-operator">-l</span> -k -U <span class="hljs-variable">$SOCKET</span>         <span class="hljs-comment"># &#xADF8; &#xC544;&#xB798; nc &#xBA85;&#xB839;&#xC774; &#xC2E4;&#xD589;&#xB418;&#xB294;&#xB370; &#xC774;&#xB54C; $SERVER_PID &#xAC12;&#xC774;</span>
    }                                    <span class="hljs-comment"># subshell &#xC758; PID &#xAC00; &#xB429;&#xB2C8;&#xB2E4;. &#xB530;&#xB77C;&#xC11C; $SERVER_PID</span>
                                         <span class="hljs-comment"># &#xAC12;&#xC774; nc &#xBA85;&#xB839;&#xC774; &#xB418;&#xAC8C;&#xD558;&#xAE30; &#xC704;&#xD574; exec &#xC73C;&#xB85C; &#xC2E4;&#xD589;&#xD569;&#xB2C8;&#xB2E4;.</span>
    <span class="hljs-built_in">echo</span> <span class="hljs-variable">$SERVER_PID</span> &gt; <span class="hljs-variable">$PIDFILE</span>

    {
        <span class="hljs-keyword">while</span> <span class="hljs-built_in">read</span> -r; <span class="hljs-keyword">do</span>                <span class="hljs-comment"># nc -l &#xBA85;&#xB839;&#xC73C;&#xB85C;&#xBD80;&#xD130; &#xBA54;&#xC2DC;&#xC9C0;&#xAC00; read &#xAC00; &#xB418;&#xACE0;</span>
            <span class="hljs-built_in">echo</span> <span class="hljs-string">&quot;pong <span class="hljs-variable">$REPLY</span>&quot;</span>           <span class="hljs-comment"># pong &#xC744; &#xCD94;&#xAC00;&#xD55C; &#xD6C4;&#xC5D0; &#xB2E4;&#xC2DC; nc &#xBA85;&#xB839;&#xC73C;&#xB85C; &#xC804;&#xB2EC;&#xB429;&#xB2C8;&#xB2E4;. </span>
        <span class="hljs-keyword">done</span>
    } &lt;&amp; <span class="hljs-variable">${SERVER[0]}</span> &gt;&amp; <span class="hljs-variable">${SERVER[1]}</span>

    rm <span class="hljs-operator">-f</span> <span class="hljs-variable">$PIDFILE</span>                       <span class="hljs-comment"># kill &#xBA85;&#xB839;&#xC5D0; &#xC758;&#xD574; nc -l &#xBA85;&#xB839;&#xC774; &#xC885;&#xB8CC;&#xD558;&#xBA74; </span>
    rm <span class="hljs-operator">-f</span> <span class="hljs-variable">$SOCKET</span>                        <span class="hljs-comment"># pipe &#xB85C; &#xC11C;&#xB85C; &#xC5F0;&#xACB0;&#xB418;&#xC5B4; &#xC788;&#xB358; while &#xBB38;&#xB3C4; &#xC885;&#xB8CC;&#xAC00;&#xB418;&#xACE0;</span>
) &amp;                                      <span class="hljs-comment"># &#xC774;&#xC5B4;&#xC11C; rm -f &#xBA85;&#xB839;&#xC774; &#xC2E4;&#xD589;&#xB418;&#xC5B4; &#xD30C;&#xC77C;&#xC774; &#xC0AD;&#xC81C;&#xB429;&#xB2C8;&#xB2E4;.</span>

-------------------------------------

$ cat client.sh 
<span class="hljs-comment">#!/bin/bash -e</span>

SOCKET=server.sock

coproc CLIENT {
    <span class="hljs-built_in">exec</span> nc -U <span class="hljs-variable">$SOCKET</span>
}

{
    <span class="hljs-built_in">echo</span> <span class="hljs-string">&quot;<span class="hljs-variable">$@</span>&quot;</span>                       <span class="hljs-comment"># &#xC778;&#xC218;&#xB85C; &#xC804;&#xB2EC;&#xD55C; &#xBA54;&#xC2DC;&#xC9C0;&#xB294; nc &#xBA85;&#xB839;&#xC744; &#xD1B5;&#xD574;</span>
    <span class="hljs-built_in">read</span> -r                         <span class="hljs-comment"># &#xC11C;&#xBC84;&#xC5D0; &#xC804;&#xB2EC;&#xB418;&#xACE0; &#xC11C;&#xBC84;&#xB85C;&#xBD80;&#xD130; &#xC751;&#xB2F5;&#xC744; read &#xD558;&#xC5EC;</span>
} &lt;&amp; <span class="hljs-variable">${CLIENT[0]}</span> &gt;&amp; <span class="hljs-variable">${CLIENT[1]}</span>

<span class="hljs-built_in">echo</span> <span class="hljs-variable">$REPLY</span>                         <span class="hljs-comment"># &#xACB0;&#xACFC;&#xB97C; &#xCD9C;&#xB825;&#xD569;&#xB2C8;&#xB2E4;.</span>

<span class="hljs-comment">#######################  &#xC2E4;&#xD589; &#xACB0;&#xACFC;  ########################</span>

$ ./server.sh           <span class="hljs-comment"># &#xBA3C;&#xC800; server.sh &#xC744; &#xC2E4;&#xD589;</span>

$ ls                    <span class="hljs-comment"># server.sock, server.pid &#xD30C;&#xC77C;&#xC774; &#xC0DD;&#xC131;&#xB428;</span>
client.sh*  server.pid  server.sh*  server.sock=

$ ./client.sh hello     <span class="hljs-comment"># client &#xAC00; &#xBA54;&#xC2DC;&#xC9C0;&#xB97C; &#xC804;&#xB2EC;&#xD558;&#xBA74; server &#xAC00; pong &#xC744; &#xCD94;&#xAC00;&#xD558;&#xC5EC; &#xC751;&#xB2F5;&#xD569;&#xB2C8;&#xB2E4;.</span>
pong hello

$ ./client.sh coproc
pong coproc

$ <span class="hljs-built_in">kill</span> $(&lt; server.pid)  <span class="hljs-comment"># kill &#xBA85;&#xB839;&#xC5D0; &#xC758;&#xD574; coproc &#xB85C; &#xC2E4;&#xD589;&#xB41C; nc &#xBA85;&#xB839;&#xC774; &#xC885;&#xB8CC;&#xB418;&#xBA74; &#xC774;&#xC5B4;&#xC11C;</span>
                        <span class="hljs-comment"># while &#xBB38;&#xC774; &#xC885;&#xB8CC;&#xB418;&#xACE0; rm -f &#xBA85;&#xB839;&#xC5D0; &#xC758;&#xD574; &#xD30C;&#xC77C;&#xC774; &#xC0AD;&#xC81C;&#xB429;&#xB2C8;&#xB2E4;.</span>
$ ls
client.sh*  server.sh*
</code></pre>
<h3 id="coproc-&#xB97C;-&#xC774;&#xC6A9;&#xD55C;-websocket-server">coproc &#xB97C; &#xC774;&#xC6A9;&#xD55C; websocket server</h3>
<p>&#xC0AC;&#xC6A9;&#xBC29;&#xBC95;&#xC740; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xB97C; &#xC2E4;&#xD589;&#xD55C; &#xD6C4;&#xC5D0; &#xBE0C;&#xB77C;&#xC6B0;&#xC800;&#xB97C; &#xC774;&#xC6A9;&#xD574; <code>http://&lt;Host&gt;:6655/</code> &#xC5D0; &#xC811;&#xC18D;&#xD55C; &#xD6C4;
shell &#xBA85;&#xB839;&#xC744; &#xC785;&#xB825;&#xD558;&#xBA74; &#xB429;&#xB2C8;&#xB2E4;.
&#xC0AC;&#xC6A9; &#xD3EC;&#xD2B8;&#xB294; &#xBE0C;&#xB77C;&#xC6B0;&#xC800; &#xC811;&#xC18D;&#xC6A9;&#xC73C;&#xB85C; 6655 &#xBC88;&#xC744;, websocket &#xC6A9;&#xC73C;&#xB85C; 6656 &#xBC88;&#xC744; &#xC0AC;&#xC6A9;&#xD569;&#xB2C8;&#xB2E4;.
&#xC885;&#xB8CC;&#xB294; &#xB3D9;&#xC77C;&#xD558;&#xAC8C; exit &#xC73C;&#xB85C; &#xD569;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment">#!/bin/bash -e</span>
<span class="hljs-comment">#####################################</span>
<span class="hljs-comment">#                                   #</span>
<span class="hljs-comment">#          WebSocket shell          #</span>
<span class="hljs-comment">#                                   #</span>
<span class="hljs-comment">#####################################</span>
<span class="hljs-comment"># Requires bash 4.x, openssl.</span>
<span class="hljs-comment"># Author: rootshell@corelogics.de</span>

<span class="hljs-comment"># &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xC640; &#xAC19;&#xC740; process group &#xC5D0; &#xC18D;&#xD558;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC5D0;&#xAC8C; TERM &#xC2E0;&#xD638;&#xB97C; &#xBCF4;&#xB0C5;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-built_in">trap</span> <span class="hljs-string">&apos;kill 0&apos;</span> EXIT

<span class="hljs-comment"># &#xC2E4;&#xC81C; websocket &#xC774; &#xC5F0;&#xACB0;&#xB418;&#xC5B4; &#xC785;,&#xCD9C;&#xB825;&#xC774; &#xC77C;&#xC5B4;&#xB098;&#xB294; &#xBD80;&#xBD84;&#xC785;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-comment"># ${d[0]} &#xAC00; nc &#xBA85;&#xB839;&#xC758; stdin &#xC5D0; &#xC5F0;&#xACB0;&#xB418;&#xACE0; ${d[1]} &#xAC00; stdout &#xC5D0; &#xC5F0;&#xACB0;&#xB429;&#xB2C8;&#xB2E4;.</span>
coproc d { <span class="hljs-built_in">exec</span> nc <span class="hljs-operator">-l</span> <span class="hljs-number">6656</span> ;}

<span class="hljs-comment"># 6655 &#xD3EC;&#xD2B8;&#xB97C; &#xB9AC;&#xC2A4;&#xB2DD;&#xC744; &#xD558;&#xACE0; &#xC788;&#xB2E4;&#xAC00; &#xBE0C;&#xB77C;&#xC6B0;&#xC800;&#xAC00; &#xC811;&#xC18D;&#xD558;&#xBA74; &#xD398;&#xC774;&#xC9C0;&#xB97C; &#xC804;&#xC1A1;&#xD569;&#xB2C8;&#xB2E4;.</span>
nc -N <span class="hljs-operator">-l</span> <span class="hljs-number">6655</span> &gt; /dev/null &lt;&lt;\ENDOFPAGE
HTTP/<span class="hljs-number">1.1</span> <span class="hljs-number">200</span> OK

&lt;html&gt;
&lt;head&gt;
    &lt;script language=<span class="hljs-string">&quot;javascript&quot;</span>&gt;
        var url = location.hostname + <span class="hljs-string">&apos;:&apos;</span> + (parseInt(location.port) + <span class="hljs-number">1</span>);
        var ws = new WebSocket(<span class="hljs-string">&apos;ws://&apos;</span> + url + <span class="hljs-string">&apos;/test&apos;</span>);
        ws.onmessage = <span class="hljs-keyword">function</span> (msg) {
            document.f.out.value += msg.data + <span class="hljs-string">&apos;\n&apos;</span>;
            document.f.out.scrollTop = document.f.out.scrollHeight;
        }
        ws.onclose = <span class="hljs-function"><span class="hljs-title">function</span></span> () { alert(<span class="hljs-string">&apos;Connection closed.&apos;</span>); }
        <span class="hljs-keyword">function</span> <span class="hljs-function"><span class="hljs-title">send</span></span>() {
            ws.send(<span class="hljs-string">&apos;&apos;</span> + document.f.in.value);
            document.f.in.value = <span class="hljs-string">&apos;&apos;</span>;
        }
    &lt;/script&gt;
&lt;/head&gt;

&lt;body&gt;
    &lt;form name=<span class="hljs-string">&quot;f&quot;</span>&gt;
        &lt;textarea name=<span class="hljs-string">&quot;out&quot;</span> cols=<span class="hljs-string">&quot;75&quot;</span> rows=<span class="hljs-string">&quot;20&quot;</span> wrap=<span class="hljs-string">&quot;off&quot;</span>&gt;&lt;/textarea&gt;
        &lt;br&gt;
        Command: &lt;input value=<span class="hljs-string">&quot;&quot;</span> <span class="hljs-built_in">type</span>=<span class="hljs-string">&quot;text&quot;</span> size=<span class="hljs-string">&quot;55&quot;</span> id=<span class="hljs-string">&quot;in&quot;</span>
            onkeypress=<span class="hljs-string">&quot;if ( event.keyCode == 13 ) { send(); return false; }&quot;</span> /&gt;
    &lt;/form&gt;
&lt;/body&gt;
&lt;/html&gt;
ENDOFPAGE

<span class="hljs-comment"># &#xC804;&#xC1A1;&#xB41C; &#xD398;&#xC774;&#xC9C0;&#xC758; javascript &#xC774; &#xC2E4;&#xD589;&#xB418;&#xC5B4; websocket &#xC774; &#xC5F0;&#xACB0;&#xB418;&#xB294; &#xBD80;&#xBD84;&#xC785;&#xB2C8;&#xB2E4;.</span>

until <span class="hljs-built_in">read</span> -r line
    line=$(<span class="hljs-built_in">echo</span> <span class="hljs-string">&quot;<span class="hljs-variable">$line</span>&quot;</span> | tr <span class="hljs-operator">-d</span> <span class="hljs-string">&apos;\r\n&apos;</span>)
    <span class="hljs-built_in">test</span> -z <span class="hljs-string">&quot;<span class="hljs-variable">$line</span>&quot;</span>
<span class="hljs-keyword">do</span>
    [ <span class="hljs-string">&quot;<span class="hljs-variable">${line:0:18}</span>&quot;</span> = <span class="hljs-string">&quot;Sec-WebSocket-Key:&quot;</span>     ] &amp;&amp; key=<span class="hljs-variable">${line:19}</span>
    [ <span class="hljs-string">&quot;<span class="hljs-variable">${line:0:22}</span>&quot;</span> = <span class="hljs-string">&quot;Sec-WebSocket-Version:&quot;</span> ] &amp;&amp; ver=<span class="hljs-variable">$line</span>
<span class="hljs-keyword">done</span> &lt;&amp; <span class="hljs-string">&quot;<span class="hljs-variable">${d[0]}</span>&quot;</span>

rkey=$( <span class="hljs-built_in">echo</span> -n <span class="hljs-variable">${key}</span><span class="hljs-number">258</span>EAFA5-E914-<span class="hljs-number">47</span>DA-<span class="hljs-number">95</span>CA-C5AB0DC85B11 |
    openssl dgst -sha1 -binary |
    base64 )

{
    <span class="hljs-built_in">echo</span> <span class="hljs-operator">-ne</span> <span class="hljs-string">&quot;HTTP/1.1 101 Switching Protocols\r\n&quot;</span>
    <span class="hljs-built_in">echo</span> <span class="hljs-operator">-ne</span> <span class="hljs-string">&quot;Upgrade: websocket\r\n&quot;</span>
    <span class="hljs-built_in">echo</span> <span class="hljs-operator">-ne</span> <span class="hljs-string">&quot;Connection: Upgrade\r\n&quot;</span>
    <span class="hljs-built_in">echo</span> <span class="hljs-operator">-ne</span> <span class="hljs-string">&quot;Sec-WebSocket-Accept: <span class="hljs-variable">${rkey}</span>\r\n&quot;</span>
    <span class="hljs-built_in">echo</span> <span class="hljs-operator">-ne</span> <span class="hljs-string">&quot;<span class="hljs-variable">${ver}</span>\r\n\r\n&quot;</span>
} &gt;&amp; <span class="hljs-string">&quot;<span class="hljs-variable">${d[1]}</span>&quot;</span>

<span class="hljs-comment"># &#xC0AC;&#xC6A9;&#xC790;&#xAC00; &#xC785;&#xB825;&#xD55C; &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD558;&#xC5EC; &#xACB0;&#xACFC;&#xB97C; ${d[1]} &#xB85C; &#xCD9C;&#xB825;&#xD558;&#xB294; &#xD568;&#xC218;&#xC785;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-function"><span class="hljs-title">do_cmd</span></span>() {
    { <span class="hljs-built_in">echo</span> <span class="hljs-operator">-e</span> <span class="hljs-string">&quot;&gt;&gt;&gt; <span class="hljs-variable">$1</span>&quot;</span>; <span class="hljs-built_in">eval</span> <span class="hljs-string">&quot;<span class="hljs-variable">$( echo -e &quot;$1&quot;)</span>&quot;</span> || <span class="hljs-literal">true</span> ;} &amp;&gt; &gt;(
    <span class="hljs-keyword">while</span> <span class="hljs-built_in">read</span> -r line; <span class="hljs-keyword">do</span>
        len=$( <span class="hljs-built_in">echo</span> -n <span class="hljs-string">&quot;<span class="hljs-variable">$line</span>&quot;</span> | wc -c )
        <span class="hljs-keyword">if</span> [ <span class="hljs-variable">$len</span> -le <span class="hljs-number">125</span> ]; <span class="hljs-keyword">then</span> 
            <span class="hljs-built_in">echo</span> <span class="hljs-operator">-ne</span> <span class="hljs-string">&quot;\x81\x<span class="hljs-variable">$( printf &apos;%02x&apos; $len )</span>&quot;</span>
        <span class="hljs-keyword">elif</span> [ <span class="hljs-variable">$len</span> -le <span class="hljs-number">65535</span> ]; <span class="hljs-keyword">then</span>
            <span class="hljs-built_in">echo</span> <span class="hljs-operator">-ne</span> <span class="hljs-string">&quot;\x81\x7e\x<span class="hljs-variable">$( printf &apos;%04x&apos; $len | 
            sed -E &apos;s#([[:xdigit:]]{2})</span>([[:xdigit:]]{2})#\1\\x\2#&apos; )&quot;</span>
        <span class="hljs-keyword">else</span>
            <span class="hljs-built_in">echo</span> <span class="hljs-operator">-ne</span> <span class="hljs-string">&quot;\x81\x7f\x<span class="hljs-variable">$( printf &apos;%016x&apos; $len | 
            sed -E &apos;:X s#([[:xdigit:]]{2})</span>([[:xdigit:]]{2})#\1\\x\2; tX#&apos; )&quot;</span>
        <span class="hljs-keyword">fi</span>
        <span class="hljs-built_in">echo</span> -n <span class="hljs-string">&quot;<span class="hljs-variable">$line</span>&quot;</span>
    <span class="hljs-keyword">done</span> )
} &gt;&amp; <span class="hljs-string">&quot;<span class="hljs-variable">${d[1]}</span>&quot;</span>

<span class="hljs-comment"># &#xC774;&#xC81C;&#xBD80;&#xD130; stdin &#xC785;&#xB825;&#xC740; ${d[0]} &#xB85C; &#xBD80;&#xD130; &#xBC1B;&#xC2B5;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-built_in">exec</span> &lt;&amp; <span class="hljs-string">&quot;<span class="hljs-variable">${d[0]}</span>&quot;</span>

<span class="hljs-comment"># while loop &#xB97C; &#xC774;&#xC6A9;&#xD574; ${d[0]} &#xB85C; &#xBD80;&#xD130; &#xC0AC;&#xC6A9;&#xC790; &#xC785;&#xB825;&#xC744; &#xBC1B;&#xC544; do_cmd() &#xD568;&#xC218;&#xB97C; &#xD638;&#xCD9C;&#xD569;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-keyword">while</span> <span class="hljs-literal">true</span>; <span class="hljs-keyword">do</span>
    reclen=$(( `od -An -j1 -N1 -tdI` - <span class="hljs-number">128</span> ))
    <span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> `seq <span class="hljs-number">0</span> <span class="hljs-number">3</span>`; <span class="hljs-keyword">do</span> 
        mk[i]=$( od -An -N1 -tdI )
    <span class="hljs-keyword">done</span>

    cmd=<span class="hljs-string">&quot;&quot;</span>
    <span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> `seq <span class="hljs-number">0</span> $((reclen - <span class="hljs-number">1</span>))`; <span class="hljs-keyword">do</span>
        bt=$( od -An -N1 -tdI )
        bt=$(( bt ^ <span class="hljs-variable">${mk[ $((i % 4)) ]}</span> ))
        cmd+=<span class="hljs-string">&apos;\x&apos;</span>$(<span class="hljs-built_in">printf</span> <span class="hljs-string">&apos;%02x&apos;</span> <span class="hljs-variable">$bt</span>)
    <span class="hljs-keyword">done</span>

    [ <span class="hljs-built_in">exit</span> = <span class="hljs-string">&quot;<span class="hljs-variable">$( echo -e &quot;$cmd&quot; )</span>&quot;</span> ] &amp;&amp; <span class="hljs-built_in">exit</span>

    <span class="hljs-keyword">do</span>_cmd <span class="hljs-string">&quot;<span class="hljs-variable">$cmd</span>&quot;</span>
<span class="hljs-keyword">done</span>
</code></pre>
<h4 id="ttyd-&#xBA85;&#xB839;">ttyd &#xBA85;&#xB839;</h4>
<p>ttyd &#xBA85;&#xB839;&#xC744; &#xC774;&#xC6A9;&#xD558;&#xBA74; &#xC190;&#xC27D;&#xAC8C; &#xC6F9;&#xC5D0;&#xC11C; &#xD130;&#xBBF8;&#xB110;&#xC744; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<p><a href="https://github.com/tsl0922/ttyd" target="_blank">https://github.com/tsl0922/ttyd</a></p>

                    
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