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                            <b>2.4.</b>
                        
                        Exit Status
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                        Pattern Matching
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                        Interactive vs Non-Interactive Shell
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                        Login vs Non-Login Shell
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                        etc
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                        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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                        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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                        getopts
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                        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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                            <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-">
                    
                        <h1 id="exit-status">Exit Status</h1>
<p>&#xD130;&#xBBF8;&#xB110;&#xC5D0;&#xC11C; &#xBA85;&#xB839;&#xC744; &#xB2E8;&#xACC4;&#xC801;&#xC73C;&#xB85C; &#xC2E4;&#xD589;&#xD574;&#xC11C; &#xC791;&#xC5C5;&#xC744; &#xC644;&#xC131;&#xD560; &#xB54C;&#xB294;
&#xC5EC;&#xD0DC;&#xAE4C;&#xC9C0; &#xC2E4;&#xD589;&#xD55C; &#xBA85;&#xB839;&#xB4E4;&#xC774; &#xBAA8;&#xB450; &#xC815;&#xC0C1;&#xC801;&#xC73C;&#xB85C; &#xC644;&#xB8CC;&#xB418;&#xC5C8;&#xAE30; &#xB54C;&#xBB38;&#xC5D0; &#xAC00;&#xB2A5;&#xD55C; &#xAC83;&#xC778;&#xB370;&#xC694;.
&#xAC00;&#xB839; cd &#xB97C; &#xD558;&#xACE0;, &#xC778;&#xD130;&#xB137;&#xC5D0;&#xC11C; &#xD30C;&#xC77C;&#xC744; &#xB2E4;&#xC6B4;&#xBC1B;&#xACE0;, &#xC555;&#xCD95;&#xC744; &#xD480;&#xACE0; ... &#xD558;&#xB294; &#xACFC;&#xC815;&#xC5D0;&#xC11C;
&#xD558;&#xB098;&#xB77C;&#xB3C4; &#xC624;&#xB958;&#xAC00; &#xBC1C;&#xC0DD;&#xD55C;&#xB2E4;&#xBA74; &#xC804;&#xCCB4; &#xC791;&#xC5C5;&#xC774; &#xC644;&#xC131;&#xB420; &#xC218; &#xC5C6;&#xACA0;&#xC8E0;.
&#xB530;&#xB77C;&#xC11C; &#xC55E;&#xC120; &#xBA85;&#xB839;&#xC774; &#xC815;&#xC0C1;&#xC801;&#xC73C;&#xB85C; &#xC2E4;&#xD589;&#xC744; &#xC644;&#xB8CC;&#xD588;&#xB294;&#xC9C0;, &#xC544;&#xB2C8;&#xBA74; &#xC624;&#xB958;&#xAC00; &#xBC1C;&#xC0DD;&#xD588;&#xB294;&#xC9C0;&#xB97C;
&#xD310;&#xB2E8;&#xD560; &#xC218; &#xC788;&#xB294; &#xBC29;&#xBC95;&#xC774; &#xD544;&#xC694;&#xD55C;&#xB370; &#xC774;&#xAC83;&#xC774; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xD558;&#xB294; &#xC5ED;&#xD560;&#xC785;&#xB2C8;&#xB2E4;.
&#xC2E4;&#xC81C; shell &#xC5D0;&#xC11C; &#xC81C;&#xC77C; &#xC911;&#xC694;&#xD55C; &#xAC1C;&#xB150;&#xC911; &#xD558;&#xB098;&#xAC00; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12; &#xC785;&#xB2C8;&#xB2E4;.</p>
<p>shell &#xC5D0;&#xC11C; &#xC2E4;&#xD589;&#xB418;&#xB294; &#xBAA8;&#xB4E0; &#xBA85;&#xB839;&#xC740; &#xBE60;&#xC9D0;&#xC5C6;&#xC774; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xBC18;&#xD658;&#xD569;&#xB2C8;&#xB2E4;.
<code>if</code>, <code>while</code>, <code>until</code>, <code>&amp;&amp;</code>, <code>||</code>  &#xBAA8;&#xB450; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xC0AC;&#xC6A9;&#xD574;&#xC11C; &#xCC38;, &#xAC70;&#xC9D3;&#xC744; &#xD310;&#xB2E8;&#xD569;&#xB2C8;&#xB2E4;.
&#xAE30;&#xBCF8;&#xC801;&#xC73C;&#xB85C; &#xBA85;&#xB839;&#xC774; &#xC815;&#xC0C1; &#xC885;&#xB8CC;&#xD558;&#xC600;&#xC744; &#xACBD;&#xC6B0;&#xB294; <code>0</code> &#xC744; &#xBC18;&#xD658;&#xD558;&#xACE0; 
&#xADF8; &#xC774;&#xC678;&#xC758; &#xAC12;&#xB4E4;&#xC740; &#xC624;&#xB958;&#xB97C; &#xBD84;&#xB958;&#xD558;&#xB294; &#xC6A9;&#xB3C4;&#xB85C; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.
&#xD504;&#xB85C;&#xADF8;&#xB798;&#xBC0D; &#xC5B8;&#xC5B4;&#xC5D0;&#xC11C;&#xCC98;&#xB7FC; &#xD2B9;&#xC815;&#xAC12; ( &#xC2A4;&#xD2B8;&#xB9C1; &#xB610;&#xB294; &#xC608;&#xC57D;&#xC5B4; ) &#xB97C; &#xC0AC;&#xC6A9;&#xD558;&#xC9C0; &#xC54A;&#xC2B5;&#xB2C8;&#xB2E4;. </p>
<p>&#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC740; <code>$?</code> &#xBCC0;&#xC218;&#xB97C; &#xD1B5;&#xD574; &#xC54C;&#xC544;&#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ date
Wed Feb <span class="hljs-number">20</span> <span class="hljs-number">10</span>:<span class="hljs-number">54</span>:<span class="hljs-number">04</span> KST <span class="hljs-number">2019</span>

$ <span class="hljs-built_in">echo</span> $?                      <span class="hljs-comment"># &#xC815;&#xC0C1; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC740; &apos;0&apos;</span>
<span class="hljs-number">0</span>

$ date -@
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.

$ <span class="hljs-built_in">echo</span> $?                      <span class="hljs-comment"># &apos;0&apos; &#xC774;&#xC678;&#xC758; &#xAC12;&#xC740; &#xC624;&#xB958;&#xB97C; &#xB098;&#xD0C0;&#xB0C4;</span>
<span class="hljs-number">1</span>
..........................................................

curl -O ftp.kaist.ac.kr/ubuntu-cd/bionic/ubuntu-desktop-amd64.iso

<span class="hljs-keyword">if</span> <span class="hljs-built_in">test</span> $? = <span class="hljs-number">0</span>; <span class="hljs-keyword">then</span> 
    <span class="hljs-built_in">echo</span> <span class="hljs-string">&quot;download succeeded&quot;</span>
<span class="hljs-keyword">else</span> 
    <span class="hljs-built_in">echo</span> <span class="hljs-string">&quot;download failed&quot;</span>
<span class="hljs-keyword">fi</span>
</code></pre>
<p>&#xC885;&#xB8CC;&#xCF54;&#xB4DC; <code>0</code> &#xC774; &#xCC38;&#xC774;&#xB77C;&#xACE0; &#xD574;&#xC11C; &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ <span class="hljs-keyword">if</span> <span class="hljs-number">0</span>; <span class="hljs-keyword">then</span> <span class="hljs-built_in">echo</span> <span class="hljs-number">111</span>; <span class="hljs-keyword">else</span> <span class="hljs-built_in">echo</span> <span class="hljs-number">222</span>; <span class="hljs-keyword">fi</span>
<span class="hljs-number">0</span>: <span class="hljs-built_in">command</span> not found

$ <span class="hljs-number">0</span> &amp;&amp; <span class="hljs-built_in">echo</span> <span class="hljs-number">111</span>
<span class="hljs-number">0</span>: <span class="hljs-built_in">command</span> not found
</code></pre>
<h3 id="&#xC55E;&#xC120;-&#xBA85;&#xB839;&#xC774;-&#xC815;&#xC0C1;-&#xC885;&#xB8CC;&#xB418;&#xC5B4;&#xC57C;-&#xD560;-&#xACBD;&#xC6B0;">&#xC55E;&#xC120; &#xBA85;&#xB839;&#xC774; &#xC815;&#xC0C1; &#xC885;&#xB8CC;&#xB418;&#xC5B4;&#xC57C; &#xD560; &#xACBD;&#xC6B0;</h3>
<p>&#xC55E;&#xC11C; &#xC2E4;&#xD589;&#xB41C; &#xBA85;&#xB839;&#xC774; &#xC624;&#xB958;&#xB85C; &#xC885;&#xB8CC;&#xD558;&#xC600;&#xC744; &#xACBD;&#xC6B0;
&#xB4A4;&#xC5D0; &#xC774;&#xC5B4;&#xC9C0;&#xB294; &#xBA85;&#xB839;&#xC774; &#xC2E4;&#xD589;&#xB418;&#xBA74; &#xC548;&#xB420; &#xACBD;&#xC6B0;&#xAC00; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xC774;&#xB7F4; &#xB54C;&#xB294; &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774; <code>&amp;&amp;</code> &#xC5F0;&#xC0B0;&#xC790;&#xB97C; &#xC774;&#xC6A9;&#xD574; &#xBA85;&#xB839;&#xC744; &#xC5F0;&#xACB0;&#xD558;&#xAC70;&#xB098;
test &#xBA85;&#xB839;&#xC744; &#xC774;&#xC6A9;&#xD574; &#xC9C1;&#xC811; <code>$?</code> &#xAC12;&#xC744; &#xCCB4;&#xD06C;&#xD569;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ <span class="hljs-built_in">command</span>1 ... &amp;&amp; <span class="hljs-built_in">command</span>2 ... &amp;&amp; <span class="hljs-built_in">command</span>3 ...

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

<span class="hljs-built_in">command</span>1 ....

<span class="hljs-keyword">if</span> <span class="hljs-built_in">test</span> $? != <span class="hljs-number">0</span>; <span class="hljs-keyword">then</span>
    <span class="hljs-built_in">echo</span> <span class="hljs-built_in">command</span> failed
    <span class="hljs-built_in">exit</span> <span class="hljs-number">1</span>
<span class="hljs-keyword">fi</span>
</code></pre>
<p>&#xC55E;&#xC120; &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xACFC; &#xC0C1;&#xAD00;&#xC5C6;&#xC774; &#xC774;&#xD6C4; &#xBA85;&#xB839;&#xC774; &#xC2E4;&#xD589;&#xB418;&#xB824;&#xBA74;</p>
<pre><code class="lang-bash">$ <span class="hljs-built_in">command</span>1 ...; <span class="hljs-built_in">command</span>2 ...; <span class="hljs-built_in">command</span>3 ...
</code></pre>
<h3 id="&#xC885;&#xB8CC;-&#xC0C1;&#xD0DC;-&#xAC12;-&#xC9C0;&#xC815;">&#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12; &#xC9C0;&#xC815;</h3>
<p>&#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; &#xD30C;&#xC77C;&#xC774;&#xB098; subshell &#xC740; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xC0C8;&#xB85C; &#xC0DD;&#xC131;&#xB418;&#xB294; &#xAC83;&#xC774;&#xBBC0;&#xB85C; 
&#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xC9C0;&#xC815;&#xD560;&#xB54C; <code>exit</code> &#xBA85;&#xB839;&#xC73C;&#xB85C; &#xD569;&#xB2C8;&#xB2E4;.
function &#xC774;&#xB098; source &#xBA85;&#xB839;&#xC73C;&#xB85C; &#xC77D;&#xC5B4;&#xB4E4;&#xC774;&#xB294; &#xACBD;&#xC6B0;&#xC5D0;&#xB294; <code>return</code> &#xBA85;&#xB839;&#xC73C;&#xB85C; &#xD569;&#xB2C8;&#xB2E4;.
&#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xC9C0;&#xC815;&#xD558;&#xC9C0; &#xC54A;&#xC73C;&#xBA74; &#xB9C8;&#xC9C0;&#xB9C9;&#xC73C;&#xB85C; &#xC2E4;&#xD589;&#xB41C; &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.
&#xB530;&#xB77C;&#xC11C; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; &#xC791;&#xC131;&#xC2DC; &#xC9C1;&#xC811; <code>$?</code> &#xBCC0;&#xC218;&#xB97C; &#xC0AC;&#xC6A9;&#xD574;&#xC57C; &#xB418;&#xB294; &#xACBD;&#xC6B0;&#xB294; &#xB9CE;&#xC9C0; &#xC54A;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xB9C8;&#xC9C0;&#xB9C9; &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xC0AC;&#xC6A9;&#xB418;&#xBBC0;&#xB85C; &#xB530;&#xB85C; return &#xBA85;&#xB839;&#xC744; &#xC0AC;&#xC6A9;&#xD560; &#xD544;&#xC694;&#xAC00; &#xC5C6;&#xB2E4;.</span>
<span class="hljs-function"><span class="hljs-title">command_exist</span></span> () {
    <span class="hljs-built_in">which</span> <span class="hljs-string">&quot;<span class="hljs-variable">$1</span>&quot;</span> &gt; /dev/null;
    <span class="hljs-comment"># return $?</span>
}

<span class="hljs-keyword">if</span> <span class="hljs-built_in">command</span>_exist vim; <span class="hljs-keyword">then</span>
    ...
<span class="hljs-keyword">fi</span>
--------------------------------------------------------------------------------

<span class="hljs-comment"># &#xB2E4;&#xC74C;&#xC758; &#xACBD;&#xC6B0;&#xB294; &#xD568;&#xC218; &#xC911;&#xAC04;&#xC5D0;&#xC11C; return &#xBA85;&#xB839;&#xC744; &#xC0AC;&#xC6A9;&#xD558;&#xC600;&#xC9C0;&#xB9CC; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xC9C0;&#xC815;&#xD558;&#xC9C0; &#xC54A;&#xC558;&#xB294;&#xB370;&#xC694;.</span>
<span class="hljs-comment"># &#xC774;&#xB54C;&#xB3C4; &#xC790;&#xB3D9;&#xC73C;&#xB85C; &#xB9C8;&#xC9C0;&#xB9C9; &#xBA85;&#xB839; builtin cd &quot;$@&quot; &#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;. </span>
<span class="hljs-keyword">function</span> <span class="hljs-function"><span class="hljs-title">cd</span></span>() {
    ...
    <span class="hljs-built_in">builtin</span> <span class="hljs-built_in">cd</span> <span class="hljs-string">&quot;<span class="hljs-variable">$@</span>&quot;</span>
    <span class="hljs-built_in">return</span>
    ...
    ...
}
---------------------------------------

$ <span class="hljs-function"><span class="hljs-title">func1</span></span>() { <span class="hljs-literal">true</span> &amp;&amp; <span class="hljs-built_in">return</span>; <span class="hljs-built_in">echo</span> end... ;}   
$ func1
$ <span class="hljs-built_in">echo</span> $?     <span class="hljs-comment"># &#xB9C8;&#xC9C0;&#xB9C9;&#xC5D0; &#xC2E4;&#xD589;&#xB41C; true &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xB41C;&#xB2E4;.</span>
<span class="hljs-number">0</span>

$ <span class="hljs-function"><span class="hljs-title">func1</span></span>() { <span class="hljs-literal">false</span> || <span class="hljs-built_in">return</span>; <span class="hljs-built_in">echo</span> end... ;}  
$ func1
$ <span class="hljs-built_in">echo</span> $?     <span class="hljs-comment"># &#xB9C8;&#xC9C0;&#xB9C9;&#xC5D0; &#xC2E4;&#xD589;&#xB41C; false &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xB41C;&#xB2E4;.</span>
<span class="hljs-number">1</span>

$ ( <span class="hljs-literal">true</span> &amp;&amp; <span class="hljs-built_in">exit</span>; <span class="hljs-built_in">echo</span> end... ); <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">0</span>

$ ( <span class="hljs-literal">false</span> || <span class="hljs-built_in">exit</span>; <span class="hljs-built_in">echo</span> end... ); <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">1</span>
</code></pre>
<p>&#xB9CC;&#xC57D;&#xC5D0; &#xBA85;&#xB839;&#xC774; &#xC624;&#xB958;&#xB85C; &#xC885;&#xB8CC;&#xD558;&#xC600;&#xB294;&#xB370; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC73C;&#xB85C;&#xB294; <code>0</code> &#xC744; &#xBC18;&#xD658;&#xD558;&#xB824;&#xBA74; &#xC774;&#xB54C;&#xB294; &#xC9C1;&#xC811; &#xC9C0;&#xC815;&#xC744; &#xD574;&#xC57C;&#xACA0;&#xC8E0;</p>
<pre><code class="lang-bash">error_<span class="hljs-built_in">command</span> ... || <span class="hljs-built_in">return</span> <span class="hljs-number">0</span>

error_<span class="hljs-built_in">command</span> ... || <span class="hljs-built_in">exit</span> <span class="hljs-number">0</span>
</code></pre>
<hr>
<p>&#xC885;&#xB8CC;&#xCF54;&#xB4DC;&#xC5D0;&#xB294; 1 byte &#xAC00; &#xC0AC;&#xC6A9;&#xB418;&#xBBC0;&#xB85C;  0 ~ 255 &#xBC88;&#xC744; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xADF8;&#xC911;&#xC5D0; <code>0</code> &#xB9CC; &#xC815;&#xC0C1; &#xC885;&#xB8CC;&#xB97C; &#xB098;&#xD0C0;&#xB0B4;&#xACE0; &#xB098;&#xBA38;&#xC9C0;&#xB294; &#xC624;&#xB958;&#xB97C; &#xBD84;&#xB958;&#xD574; &#xB098;&#xD0C0;&#xB0B4;&#xB294;&#xB370; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.
shell &#xC5D0;&#xC11C;&#xB294; &#xC77C;&#xBC18;&#xC801;&#xC73C;&#xB85C; &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC740; &#xBC29;&#xC2DD;&#xC73C;&#xB85C; &#xC624;&#xB958;&#xB97C; &#xBD84;&#xB958;&#xD558;&#xACE0; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<h3 id="0">0</h3>
<p>&#xC815;&#xC0C1;&#xC885;&#xB8CC; ( Success )  </p>
<h3 id="1">1</h3>
<p>&#xC77C;&#xBC18;&#xC801;&#xC778; &#xC5D0;&#xB7EC;</p>
<blockquote>
<p>let &quot;var = 1 / 0&quot; : division by 0</p>
</blockquote>
<h3 id="2">2</h3>
<p>Syntax error, &#xC798;&#xBABB; &#xC0AC;&#xC6A9;&#xB41C; builtin &#xBA85;&#xB839; </p>
<blockquote>
<p>test.sh: line 6: syntax error near unexpected token &apos;fi&apos;<br>exit: 3.14: numeric argument required  </p>
</blockquote>
<h3 id="126">126</h3>
<p>&#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD560; &#xC218; &#xC5C6;&#xC74C;</p>
<blockquote>
<p>&#xBA85;&#xB839;&#xC740; &#xC874;&#xC7AC;&#xD558;&#xC9C0;&#xB9CC; excutable &#xC774; &#xC544;&#xB2C8;&#xAC70;&#xB098; &#xD37C;&#xBBF8;&#xC158; &#xBB38;&#xC81C;<br>bash: ./mylogfile.txt: Permission denied</p>
</blockquote>
<h3 id="127">127</h3>
<p>&#xBA85;&#xB839; (&#xD30C;&#xC77C;) &#xC774; &#xC874;&#xC7AC;&#xD558;&#xC9C0; &#xC54A;&#xC74C;</p>
<blockquote>
<p>typo &#xB610;&#xB294; <code>$PATH</code> &#xBB38;&#xC81C;<br>asdfg: command not found</p>
</blockquote>
<h3 id="128--n">128 + N</h3>
<p>Signal N &#xC5D0;&#xC758;&#xD55C; &#xC885;&#xB8CC;.</p>
<blockquote>
<p>&#xAC00;&#xB839; kill -9 PID &#xB85C; &#xC885;&#xB8CC; &#xB410;&#xB2E4;&#xBA74; <code>$?</code> &#xAC12;&#xC740; 128 + 9 = 137</p>
</blockquote>
<h3 id="&#xCC38;-&#xAC70;&#xC9D3;-&#xD310;&#xB2E8;&#xC5D0;-&#xBCF5;&#xC218;&#xAC1C;&#xC758;-&#xBA85;&#xB839;&#xC774;-&#xC0AC;&#xC6A9;&#xB420;-&#xACBD;&#xC6B0;">&#xCC38;, &#xAC70;&#xC9D3; &#xD310;&#xB2E8;&#xC5D0; &#xBCF5;&#xC218;&#xAC1C;&#xC758; &#xBA85;&#xB839;&#xC774; &#xC0AC;&#xC6A9;&#xB420; &#xACBD;&#xC6B0;</h3>
<p>&#xCC38;, &#xAC70;&#xC9D3;&#xC758; &#xD310;&#xB2E8;&#xC5D0; &#xC0AC;&#xC6A9;&#xB418;&#xB294; &#xBA85;&#xB839;&#xC774; &#xC704;&#xCE58;&#xD558;&#xB294; &#xC790;&#xB9AC;&#xC5D0;&#xB294; &#xAF2D; &#xD558;&#xB098;&#xC758; &#xBA85;&#xB839;&#xB9CC; &#xC62C;&#xC218; &#xC788;&#xB294; &#xAC83;&#xC740; &#xC544;&#xB2D9;&#xB2C8;&#xB2E4;.
<code>&amp;&amp;</code>, <code>||</code> &#xB610;&#xB294; <code>{ ;}</code>, <code>( )</code> &#xB97C; &#xC774;&#xC6A9;&#xD55C; &#xBA85;&#xB839; &#xADF8;&#xB8F9;&#xC774; &#xC62C; &#xC218;&#xB3C4; &#xC788;&#xACE0; <code>;</code> &#xB97C; &#xC774;&#xC6A9;&#xD574;&#xC11C; &#xC5EC;&#xB7EC;&#xAC1C;&#xC758; &#xBA85;&#xB839;&#xC744; &#xC0AC;&#xC6A9;&#xD560; &#xC218;&#xB3C4; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xB610;&#xD55C; <code>|</code> &#xD30C;&#xC774;&#xD504;&#xB97C; &#xC774;&#xC6A9;&#xD574;&#xC11C; &#xC5EC;&#xB7EC; &#xBA85;&#xB839;&#xC774; &#xC5F0;&#xACB0;&#xB420; &#xC218;&#xB3C4; &#xC788;&#xB294;&#xB370; &#xC5B4;&#xB5A4; &#xACBD;&#xC6B0;&#xC774;&#xAC74; &#xBAA8;&#xB450; &#xB9C8;&#xC9C0;&#xB9C9;&#xC73C;&#xB85C; &#xC2E4;&#xD589;&#xB418;&#xB294; &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xCC38;, &#xAC70;&#xC9D3;&#xC758; &#xD310;&#xB2E8;&#xC5D0; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xB9C8;&#xC9C0;&#xB9C9; &#xBA85;&#xB839;&#xC778; test -z &#xC758; &#xC885;&#xB8CC;&#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xCC38;, &#xAC70;&#xC9D3; &#xD310;&#xB2E8;&#xC5D0; &#xC0AC;&#xC6A9;&#xB41C;&#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">$line</span>&quot;</span>
<span class="hljs-keyword">do</span>
    ...
<span class="hljs-keyword">done</span>
</code></pre>
<p><a name="pipe"></a></p>
<h3 id="pipe-&#xB85C;-&#xC5F0;&#xACB0;&#xB41C;-&#xBA85;&#xB839;&#xC758;-&#xC885;&#xB8CC;-&#xC0C1;&#xD0DC;-&#xAC12;">pipe &#xB85C; &#xC5F0;&#xACB0;&#xB41C; &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;</h3>
<p>pipe &#xB85C; &#xC5EC;&#xB7EC; &#xBA85;&#xB839;&#xC774; &#xC5F0;&#xACB0;&#xB418;&#xC5B4; &#xC2E4;&#xD589;&#xB420; &#xB54C;&#xB294; &#xB9C8;&#xC9C0;&#xB9C9; &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.
&#xB530;&#xB77C;&#xC11C; &#xB2E4;&#xC74C; &#xCCAB;&#xBC88;&#xC9F8; &#xBA85;&#xB839;&#xBB38;&#xC740; &#xD56D;&#xC0C1; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC73C;&#xB85C; <code>0</code> &#xC744; &#xBC18;&#xD658;&#xD569;&#xB2C8;&#xB2E4;.
&#xC65C;&#xB0D0;&#xD558;&#xBA74; command1 &#xC758; &#xC2E4;&#xD328;&#xC5D0; &#xC0C1;&#xAD00;&#xC5C6;&#xC774; sed &#xBA85;&#xB839;&#xC740; &#xD56D;&#xC0C1; &#xCC38;&#xC744; &#xBC18;&#xD658;&#xD558;&#xAE30; &#xB54C;&#xBB38;&#xC785;&#xB2C8;&#xB2E4;.
command1 &#xBA85;&#xB839;&#xC774; &#xC2E4;&#xD328;&#xD558;&#xC600;&#xC744; &#xB54C; &#xBE44;&#xC815;&#xC0C1; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xBC18;&#xD658;&#xB418;&#xB824;&#xBA74;
&#xB450; &#xBC88;&#xC9F8;&#xC640; &#xAC19;&#xC774; pipefail &#xC635;&#xC158;&#xC744; &#xC0AC;&#xC6A9;&#xD574;&#xC57C; &#xD569;&#xB2C8;&#xB2E4;.
pipefail &#xC635;&#xC158;&#xC740; &#xD30C;&#xC774;&#xD504;&#xC5D0; &#xC5F0;&#xACB0;&#xB41C; &#xBA85;&#xB839;&#xB4E4; &#xC911;&#xC5D0; &#xD558;&#xB098;&#xB77C;&#xB3C4; &#xC624;&#xB958;&#xAC00; &#xC0DD;&#xAE38; &#xACBD;&#xC6B0;
&#xBE44;&#xC815;&#xC0C1; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xBC18;&#xD658;&#xD569;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">
    <span class="hljs-built_in">command</span>1 arg1 arg2 | sed -n <span class="hljs-string">&apos;/&lt;main&gt;:/,/^$/p&apos;</span>

..................................................

<span class="hljs-comment"># &#xC635;&#xC158; &#xC124;&#xC815;&#xC774; &#xD604;&#xC7AC; shell &#xC5D0; &#xC801;&#xC6A9;&#xB418;&#xC9C0; &#xC54A;&#xB3C4;&#xB85D; subshell &#xC744; &#xC0AC;&#xC6A9;.</span>
(
    <span class="hljs-built_in">set</span> -o pipefail
    <span class="hljs-built_in">command</span>1 arg1 arg2 | sed -n <span class="hljs-string">&apos;/&lt;main&gt;:/,/^$/p&apos;</span>
)
</code></pre>
<p><code>sh</code> &#xC758; &#xACBD;&#xC6B0;&#xB294; pipefail &#xC635;&#xC158;&#xC744; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC5C6;&#xC73C;&#xBBC0;&#xB85C; &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774; &#xBA85;&#xB839;&#xC744; &#xBD84;&#xB9AC;&#xD574; &#xC791;&#xC131;&#xD558;&#xAC70;&#xB098;
<a href="redirections.html#quiz-pipefail">redirections &#xC608;&#xC81C;</a> &#xC640; &#xAC19;&#xC740; &#xBC29;&#xBC95;&#xC744; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xBA85;&#xB839;&#xC744; &#xB450;&#xAC1C;&#xB85C; &#xBD84;&#xB9AC;&#xD574;&#xC11C; &#xC791;&#xC131;</span>
<span class="hljs-built_in">command</span>1 arg1 arg2 &gt; tmpfile

status=$?

sed -n <span class="hljs-string">&apos;/&lt;main&gt;:/,/^$/p&apos;</span> tmpfile

<span class="hljs-built_in">echo</span> <span class="hljs-variable">$status</span>
</code></pre>
<h3 id="null-&#xAC12;&#xC778;-&#xBCC0;&#xC218;&#xB294;-&#xCC38;&#xC77C;&#xAE4C;-&#xAC70;&#xC9D3;&#xC77C;&#xAE4C;">null &#xAC12;&#xC778; &#xBCC0;&#xC218;&#xB294; &#xCC38;&#xC77C;&#xAE4C; &#xAC70;&#xC9D3;&#xC77C;&#xAE4C;?</h3>
<p>&#xC874;&#xC7AC;&#xD558;&#xC9C0; &#xC54A;&#xB294; &#xBCC0;&#xC218;&#xB098; null &#xAC12;&#xC778; &#xBCC0;&#xC218;&#xB294; quote &#xD558;&#xC9C0; &#xC54A;&#xC744;&#xACBD;&#xC6B0; &#xCC38;&#xC774; &#xB418;&#xBBC0;&#xB85C; &#xC8FC;&#xC758;&#xD574;&#xC57C; &#xD569;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># $asdfgh &#xB294; &#xC874;&#xC7AC;&#xD558;&#xC9C0; &#xC54A;&#xB294; &#xBCC0;&#xC218;</span>
$ <span class="hljs-keyword">if</span> <span class="hljs-variable">$asdfgh</span>; <span class="hljs-keyword">then</span> <span class="hljs-built_in">echo</span> <span class="hljs-literal">true</span>; <span class="hljs-keyword">else</span> <span class="hljs-built_in">echo</span> <span class="hljs-literal">false</span>; <span class="hljs-keyword">fi</span>
<span class="hljs-literal">true</span>

$ asdfgh=<span class="hljs-string">&quot;&quot;</span>
$ <span class="hljs-variable">$asdfgh</span> &amp;&amp; <span class="hljs-built_in">echo</span> <span class="hljs-literal">true</span>     <span class="hljs-comment"># null &#xAC12;&#xC778; &#xBCC0;&#xC218;&#xB3C4; &#xCC38;&#xC774;&#xB41C;&#xB2E4;.</span>
<span class="hljs-literal">true</span>

$ <span class="hljs-built_in">unset</span> -v asdfgh
$ <span class="hljs-variable">$asdfgh</span> &amp;&amp; <span class="hljs-built_in">echo</span> <span class="hljs-literal">true</span>     <span class="hljs-comment"># unset &#xD588;&#xC744; &#xACBD;&#xC6B0;&#xB3C4; &#xCC38;&#xC774;&#xB41C;&#xB2E4;.</span>
<span class="hljs-literal">true</span>
</code></pre>
<h3 id="&#xB300;&#xC785;-&#xC5F0;&#xC0B0;&#xC758;-&#xC885;&#xB8CC;-&#xC0C1;&#xD0DC;-&#xAC12;&#xC740;">&#xB300;&#xC785; &#xC5F0;&#xC0B0;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC740;?</h3>
<p><code>=</code> , <code>+=</code> &#xBA54;&#xD0C0;&#xBB38;&#xC790;&#xB97C; &#xC774;&#xC6A9;&#xD55C; &#xC2DD;&#xC740; &#xBA85;&#xB839;&#xBB38;&#xC774; &#xC544;&#xB2D9;&#xB2C8;&#xB2E4;.
&#xADF8;&#xB798;&#xC11C; <code>;</code> &#xB85C; &#xAD6C;&#xBD84;&#xC5C6;&#xC774; &#xD55C;&#xC904;&#xC5D0; &#xC5EC;&#xB7EC;&#xAC1C;&#xB97C; &#xC4F8; &#xC218;&#xB3C4; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC740; &#xAE30;&#xBCF8;&#xC801;&#xC73C;&#xB85C; &#xD56D;&#xC0C1; <code>0</code> &#xC774;&#xC9C0;&#xB9CC; &#xBA85;&#xB839;&#xCE58;&#xD658;&#xACFC; &#xD568;&#xAED8; &#xC0AC;&#xC6A9;&#xB418;&#xBA74; &#xBA85;&#xB839;&#xCE58;&#xD658; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774;
&#xC801;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xB300;&#xC785;&#xC5F0;&#xC0B0;&#xC740; &#xBA85;&#xB839;&#xBB38;&#xC774; &#xC544;&#xB2C8;&#xBBC0;&#xB85C; &#xD55C;&#xC904;&#xC5D0; &#xC5EC;&#xB7EC;&#xAC1C;&#xB97C; &#xC4F8;&#xC218; &#xC788;&#xB2E4;.</span>
$ AA=<span class="hljs-number">11</span> BB=<span class="hljs-number">22</span> CC=<span class="hljs-number">33</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">11</span> <span class="hljs-number">22</span> <span class="hljs-number">33</span>

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

$ <span class="hljs-built_in">test</span> <span class="hljs-number">1</span> = <span class="hljs-number">2</span>
$ <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">1</span>

$ <span class="hljs-built_in">test</span> <span class="hljs-number">1</span> = <span class="hljs-number">2</span>
$ AA=<span class="hljs-number">100</span>
$ <span class="hljs-built_in">echo</span> $?        <span class="hljs-comment"># &#xB300;&#xC785;&#xC5F0;&#xC0B0;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC740; &#xAE30;&#xBCF8;&#xC801;&#xC73C;&#xB85C; 0 &#xC774;&#xB2E4;</span>
<span class="hljs-number">0</span>

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

<span class="hljs-comment"># &#xBA85;&#xB839;&#xCE58;&#xD658;&#xACFC; &#xC0AC;&#xC6A9;&#xB420; &#xACBD;&#xC6B0; &#xBA85;&#xB839;&#xCE58;&#xD658; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xB530;&#xB978;&#xB2E4;.</span>
$ readlink <span class="hljs-operator">-e</span> asdfg; <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">1</span>
$ AA=$( readlink <span class="hljs-operator">-e</span> asdfg ); <span class="hljs-built_in">echo</span> $?    
<span class="hljs-number">1</span>

$ readlink <span class="hljs-operator">-e</span> test.sh; <span class="hljs-built_in">echo</span> $?
/home/mug896/tmp/test.sh
<span class="hljs-number">0</span>
$ AA=$(readlink <span class="hljs-operator">-e</span> test.sh); <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">0</span>
$ <span class="hljs-built_in">echo</span> <span class="hljs-variable">$AA</span>
/home/mug896/tmp/test.sh

<span class="hljs-comment"># &#xADF8;&#xB7EC;&#xBBC0;&#xB85C; if &#xBB38;&#xC5D0;&#xC11C; &#xC0AC;&#xC6A9;&#xD560; &#xC218;&#xB3C4; &#xC788;&#xB2E4;.</span>
<span class="hljs-keyword">if</span> AA=$( readlink <span class="hljs-operator">-e</span> test.sh ); <span class="hljs-keyword">then</span> ...

<span class="hljs-keyword">if</span> ! options=$(getopt -o a:f:c -- <span class="hljs-string">&quot;<span class="hljs-variable">$@</span>&quot;</span>); <span class="hljs-keyword">then</span>
    usage
    <span class="hljs-built_in">exit</span> <span class="hljs-number">1</span>
<span class="hljs-keyword">fi</span>

<span class="hljs-comment"># &#xB2E8; local, declare &#xC640; &#xD568;&#xAED8; &#xC0AC;&#xC6A9;&#xB420; &#xACBD;&#xC6B0;&#xB294; &#xC801;&#xC6A9;&#xB418;&#xC9C0; &#xC54A;&#xC2B5;&#xB2C8;&#xB2E4;.</span>
$ AA=$( readlink <span class="hljs-operator">-e</span> asdfg ); <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">1</span>
$ <span class="hljs-built_in">declare</span> AA=$( readlink <span class="hljs-operator">-e</span> asdfg ); <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">0</span>

<span class="hljs-comment"># &#xC774;&#xB54C;&#xB294; &#xBA3C;&#xC800; local, declare &#xB85C; &#xBCC0;&#xC218;&#xB97C; &#xC120;&#xC5B8;&#xD558;&#xBA74; &#xB429;&#xB2C8;&#xB2E4;.</span>
$ <span class="hljs-built_in">declare</span> AA
$ AA=$( readlink <span class="hljs-operator">-e</span> asdfg ); <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">1</span>
</code></pre>
<h1 id="quiz">Quiz</h1>
<p>ftp &#xBA85;&#xB839;&#xC744; &#xC0AC;&#xC6A9;&#xD574; &#xBCF4;&#xBA74; &#xC791;&#xC5C5; &#xC131;&#xACF5;&#xC5D0; &#xC0C1;&#xAD00;&#xC5C6;&#xC774; &#xD56D;&#xC0C1; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC73C;&#xB85C; <code>0</code> &#xC744; &#xBC18;&#xD658;&#xD558;&#xB294; &#xAC83;&#xC744; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xC774;&#xAC83;&#xC740; ftp &#xC791;&#xC5C5; &#xC2E4;&#xD328;&#xC2DC; &#xB2E4;&#xC74C; &#xC2E4;&#xD589;&#xD560; &#xBA85;&#xB839;&#xC744; &#xCEE8;&#xD2B8;&#xB864;&#xD558;&#xB294;&#xB370; &#xBB38;&#xC81C;&#xAC00; &#xB418;&#xB294;&#xB370;&#xC694;.
&#xC5B4;&#xB5BB;&#xAC8C; &#xD558;&#xBA74; &#xC791;&#xC5C5; &#xC2E4;&#xD328;&#xB97C; &#xAD6C;&#xBD84;&#xD560; &#xC218; &#xC788;&#xC744;&#xAE4C;&#xC694;?</p>
<pre><code class="lang-bash">$ ftp -in ftp.kaist.ac.kr &lt;&lt;\END 
user anonymous <span class="hljs-number">1234</span>
<span class="hljs-built_in">cd</span> /ubuntu-cd/bionic
get MD5SUMS_XXX          <span class="hljs-comment"># MD5SUMS_XXX &#xC740; &#xC874;&#xC7AC;&#xD558;&#xC9C0; &#xC54A;&#xB294; &#xD30C;&#xC77C;</span>
<span class="hljs-built_in">bye</span>
END

Failed to open file.

$ <span class="hljs-built_in">echo</span> $?                <span class="hljs-comment"># &#xC791;&#xC5C5;&#xC5D0; &#xC2E4;&#xD328;&#xD558;&#xC600;&#xC9C0;&#xB9CC;  &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC73C;&#xB85C; &apos;0&apos; &#xC774; &#xBC18;&#xD658;&#xB41C;&#xB2E4;.</span>
<span class="hljs-number">0</span>
</code></pre>
<p>ftp &#xBA85;&#xB839;&#xC758; <code>-v</code> (verbose) &#xC635;&#xC158;&#xC744; &#xC0AC;&#xC6A9;&#xD558;&#xBA74; ftp &#xC11C;&#xBC84;&#xC5D0; &#xC811;&#xC18D;&#xD574;&#xC11C; &#xC2E4;&#xD589;&#xD558;&#xB294; &#xAC01;&#xAC01;&#xC758; 
&#xBA85;&#xB839;&#xC5D0; &#xB300;&#xD574;&#xC11C; &#xC11C;&#xBC84; &#xC751;&#xB2F5;&#xC744; &#xBC1B;&#xC744; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xC774; &#xC751;&#xB2F5; &#xBA54;&#xC2DC;&#xC9C0;&#xB97C; grep &#xBA85;&#xB839;&#xC744; &#xC774;&#xC6A9;&#xD574; &#xC791;&#xC5C5; &#xC131;&#xACF5; &#xC5EC;&#xBD80;&#xB97C; &#xD310;&#xB2E8;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># login &#xC5D0; &#xC131;&#xACF5;&#xD588;&#xC744; &#xB54C; </span>
<span class="hljs-number">230</span> Login successful.

<span class="hljs-comment"># cd &#xC5D0; &#xC131;&#xACF5;&#xD588;&#xC744; &#xB54C;</span>
<span class="hljs-number">250</span> Directory successfully changed.

<span class="hljs-comment"># get file &#xC5D0; &#xC131;&#xACF5;&#xD588;&#xC744; &#xB54C;</span>
<span class="hljs-number">226</span> Transfer complete.
-----------------------------------

<span class="hljs-comment"># grep &#xBA85;&#xB839;&#xC744; &#xC774;&#xC6A9;&#xD574; &#xD30C;&#xC77C;&#xC804;&#xC1A1; &#xC131;&#xACF5; &#xC5EC;&#xBD80;&#xB97C; &#xCCB4;&#xD06C;</span>
<span class="hljs-comment"># &apos;|&apos; &#xD30C;&#xC774;&#xD504;&#xB85C; &#xBA85;&#xB839;&#xC774; &#xC5F0;&#xACB0;&#xB420; &#xACBD;&#xC6B0; &#xB9C8;&#xC9C0;&#xB9C9; &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC774; &#xC0AC;&#xC6A9;&#xB41C;&#xB2E4;.</span>
$ ftp -v -in &lt;&lt;\END | grep -q <span class="hljs-string">&apos;226 Transfer complete&apos;</span>
open ftp.kaist.ac.kr
user anonymous <span class="hljs-number">1234</span>
<span class="hljs-built_in">cd</span> /ubuntu-cd/bionic
get MD5SUMS_XXX  
<span class="hljs-built_in">bye</span>
END

$ <span class="hljs-built_in">echo</span> $?    <span class="hljs-comment"># &#xC2E4;&#xD328;</span>
<span class="hljs-number">1</span>
.....................................................

$ ftp -v -in &lt;&lt;\END | grep -q <span class="hljs-string">&apos;226 Transfer complete&apos;</span>
open ftp.kaist.ac.kr
user anonymous <span class="hljs-number">1234</span>
<span class="hljs-built_in">cd</span> /ubuntu-cd/bionic
get MD5SUMS
<span class="hljs-built_in">bye</span>
END

$ <span class="hljs-built_in">echo</span> $?    <span class="hljs-comment"># &#xC131;&#xACF5;</span>
<span class="hljs-number">0</span>
</code></pre>
<h1 id="2-">2 .</h1>
<p>&#xB300;&#xC785; &#xC5F0;&#xC0B0;&#xC2DC; <code>;</code> &#xB97C; &#xC0AC;&#xC6A9;&#xD558;&#xC9C0; &#xC54A;&#xC73C;&#xBA74; &#xC774;&#xC804; &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xC124;&#xC815;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ <span class="hljs-built_in">test</span> <span class="hljs-number">1</span> = <span class="hljs-number">2</span>
$ <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">1</span>

$ <span class="hljs-built_in">test</span> <span class="hljs-number">1</span> = <span class="hljs-number">2</span>
$ AA=<span class="hljs-number">100</span>; <span class="hljs-built_in">exit</span>=$?
$ <span class="hljs-built_in">echo</span> <span class="hljs-variable">$exit</span>          <span class="hljs-comment"># &#xC774;&#xC804; &#xBA85;&#xB839;&#xC758; &#xC885;&#xB8CC; &#xC0C1;&#xD0DC; &#xAC12;&#xC744; &#xC124;&#xC815;&#xD560; &#xC218; &#xC5C6;&#xB2E4;.</span>
<span class="hljs-number">0</span>

$ <span class="hljs-built_in">test</span> <span class="hljs-number">1</span> = <span class="hljs-number">2</span>
$ AA=<span class="hljs-number">100</span> <span class="hljs-built_in">exit</span>=$?      <span class="hljs-comment"># &apos;;&apos; &#xB97C; &#xC0AC;&#xC6A9;&#xD558;&#xC9C0; &#xC54A;&#xC73C;&#xBA74; &#xB41C;&#xB2E4;.</span>
$ <span class="hljs-built_in">echo</span> <span class="hljs-variable">$exit</span>
<span class="hljs-number">1</span>
</code></pre>

                    
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