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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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                        Operators
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                        Subshells
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                        Process Creation
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                        Commands
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                        Builtin Commands
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                        read
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                        printf
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                        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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                        Arrays
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                            <b>7.</b>
                        
                        Shell Metacharacters
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                        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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                            <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>24.</b>
                        
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                        <h2 id="session-&#xACFC;-process-group">Session &#xACFC; Process group</h2>
<p>&#xC258; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; &#xD30C;&#xC77C;&#xC744; &#xC2E4;&#xD589;&#xD558;&#xBA74; &#xB0B4;&#xBD80;&#xC801;&#xC73C;&#xB85C; &#xC5EC;&#xB7EC; &#xBA85;&#xB839;&#xB4E4;&#xC744; pipe &#xB85C; &#xC5F0;&#xACB0;&#xD574; &#xC2E4;&#xD589;&#xD560;&#xC218;&#xB3C4; &#xC788;&#xACE0;
<code>&amp;</code> &#xBB38;&#xC790;&#xB97C; &#xC774;&#xC6A9;&#xD574; background &#xB85C; &#xBA85;&#xB839;&#xB4E4;&#xC744; &#xB3D9;&#xC2DC;&#xC5D0; &#xC2E4;&#xD589;&#xD560; &#xC218;&#xB3C4; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xAC01;&#xAC01;&#xC758; &#xBA85;&#xB839;&#xB4E4;&#xC740; &#xACE0;&#xC720;&#xC758; PID &#xB97C; &#xAC16;&#xACE0; &#xC2E4;&#xD589;&#xC774; &#xB418;&#xB294;&#xB370;&#xC694;.
&#xC774;&#xB54C; &#xC2E4;&#xD589;&#xC911;&#xC778; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; &#xD30C;&#xC77C;&#xC744; &#xC885;&#xB8CC;&#xD558;&#xB824;&#xBA74; &#xC2E4;&#xD589;&#xC911;&#xC778; &#xBAA8;&#xB4E0; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC5D0; &#xC885;&#xB8CC; &#xC2E0;&#xD638;&#xB97C;
&#xBCF4;&#xB0B4;&#xC57C; &#xB429;&#xB2C8;&#xB2E4;.
&#xB530;&#xB77C;&#xC11C; &#xAD00;&#xB828;&#xB41C; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC744; &#xC880; &#xB354; &#xC27D;&#xAC8C; &#xC81C;&#xC5B4;&#xD558;&#xAE30; &#xC704;&#xD574; process group &#xC744; &#xB9CC;&#xB4E4;&#xC5B4; &#xC0AC;&#xC6A9;&#xD569;&#xB2C8;&#xB2E4;.
process group &#xC5D0; &#xC2E0;&#xD638;&#xB97C; &#xBCF4;&#xB0B4;&#xBA74; &#xAC19;&#xC740; &#xADF8;&#xB8F9;&#xC5D0; &#xC18D;&#xD55C; &#xBAA8;&#xB4E0; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC5D0; &#xC2E0;&#xD638;&#xAC00; &#xC804;&#xB2EC;&#xB429;&#xB2C8;&#xB2E4;.</p>
<p>session &#xC740; process group &#xC744; &#xD3EC;&#xD568;&#xD558;&#xB294; &#xAC1C;&#xB150;&#xC73C;&#xB85C; &#xD558;&#xB098;&#xC758; session &#xC5D0;&#xB294; &#xC5EC;&#xB7EC;&#xAC1C;&#xC758; process group
&#xC774; &#xC788;&#xC744;&#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xBCF4;&#xD1B5; session &#xC740; &#xD558;&#xB098;&#xC758; controlling terminal &#xACFC; &#xC5F0;&#xACB0;&#xB418;&#xB294;&#xB370; &#xC5EC;&#xB7EC; process group &#xB4E4;&#xC911;&#xC5D0; 
&#xD558;&#xB098;&#xB9CC; foreground process group &#xC774; &#xB418;&#xAC8C; &#xC81C;&#xC5B4;&#xD558;&#xACE0;, &#xC0AC;&#xC6A9;&#xC790;&#xB85C; &#xBD80;&#xD130; &#xC785;&#xB825;&#xC744; &#xBC1B;&#xACE0;, 
&#xBA54;&#xC2DC;&#xC9C0;&#xB97C; &#xCD9C;&#xB825;&#xD558;&#xACE0;, &#xC2E0;&#xD638;&#xB97C; &#xC804;&#xB2EC;&#xD558;&#xB294; &#xC5ED;&#xD560;&#xC744; &#xD569;&#xB2C8;&#xB2E4;.
( &#xC0AC;&#xC6A9;&#xC790;&#xAC00; Ctrl-c &#xB97C; &#xB204;&#xB974;&#xBA74; foreground process group &#xC5D0; INT &#xC2E0;&#xD638;&#xAC00; &#xC804;&#xB2EC;&#xB418;&#xACE0;,
  &#xD130;&#xBBF8;&#xB110;&#xC744; &#xC885;&#xB8CC;&#xD558;&#xC5EC; session &#xC774; &#xC885;&#xB8CC;&#xB420;&#xB54C;&#xB294; &#xBAA8;&#xB4E0; process group &#xC5D0; &#xC885;&#xB8CC; &#xC2E0;&#xD638;&#xAC00; &#xC804;&#xB2EC;&#xB429;&#xB2C8;&#xB2E4;.)</p>
<p>&#xC608;&#xB97C;&#xB4E4;&#xC5B4; &#xD130;&#xBBF8;&#xB110;&#xC744; &#xC5F4;&#xBA74; shell &#xC774; &#xC2E4;&#xD589;&#xB418;&#xB294; &#xC774;&#xB54C; shell PID &#xAC00; Session ID (SID) &#xAC00; &#xB418;&#xBA70;  session leader ( PID == SID ) &#xAC00; &#xB429;&#xB2C8;&#xB2E4;.
&#xC774;&#xD6C4; &#xD504;&#xB86C;&#xD504;&#xD2B8;&#xB97C; &#xD1B5;&#xD574; &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xC2DC;&#xCF1C; &#xC0DD;&#xC131;&#xB418;&#xB294; &#xC790;&#xC190; process &#xB4E4;&#xC740; &#xBAA8;&#xB450; &#xAC19;&#xC740; SID &#xB97C; &#xAC16;&#xAC8C;&#xB429;&#xB2C8;&#xB2E4;. </p>
<p>&#xD504;&#xB86C;&#xD504;&#xD2B8; &#xC5D0;&#xC11C; &#xC258; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xAC00; &#xC2E4;&#xD589;&#xB418;&#xBA74; process group &#xC774; &#xB9CC;&#xB4E4;&#xC5B4; &#xC9C0;&#xB294;&#xB370; &#xC774;&#xB54C; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; PID &#xAC00;
Process Group ID (PGID) &#xAC00; &#xB418;&#xBA70; process group leader ( PID == PGID ) &#xAC00; &#xB429;&#xB2C8;&#xB2E4;. 
&#xC0C8;&#xB85C; &#xC0DD;&#xC131;&#xB418;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB294; &#xBD80;&#xBAA8; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; PGID &#xB97C; &#xC0C1;&#xC18D;&#xD558;&#xBBC0;&#xB85C; &#xC774;&#xD6C4; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; &#xB0B4;&#xC5D0;&#xC11C;
&#xC2E4;&#xD589;&#xB418;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xB4E4;&#xC740; &#xBAA8;&#xB450; &#xAC19;&#xC740; PGID &#xB97C; &#xAC16;&#xAC8C;&#xB429;&#xB2C8;&#xB2E4;. </p>
<p>&#xB2E4;&#xC74C;&#xC740; &#xD504;&#xB86C;&#xD504;&#xD2B8; &#xC0C1;&#xC5D0;&#xC11C; AA.sh &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xB97C; &#xC2E4;&#xD589;&#xD55C; &#xC608;&#xC785;&#xB2C8;&#xB2E4;. 
&#xBAA8;&#xB450; bash shell PID &#xB97C; SID &#xB85C; &#xAC00;&#xC9C0;&#xACE0; &#xC788;&#xACE0; AA.sh PID &#xAC00; PGID &#xB85C; &#xC0AC;&#xC6A9;&#xB41C; &#xAC83;&#xC744; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<p><img src="images/sid_pgid_1.png" alt=""></p>
<p>&#xD30C;&#xC774;&#xD504;&#xB97C; &#xD1B5;&#xD574; &#xC5EC;&#xB7EC; &#xBA85;&#xB839;&#xC744; &#xB3D9;&#xC2DC;&#xC5D0; &#xC2E4;&#xD589;&#xC2DC;&#xD0AC; &#xB54C;&#xB3C4; process group &#xC774; &#xB9CC;&#xB4E4;&#xC5B4;&#xC9C0;&#xB294;&#xB370; &#xC774;&#xB54C;&#xB294; &#xD30C;&#xC774;&#xD504;&#xB85C; &#xC5F0;&#xACB0;&#xB41C; &#xBA85;&#xB839;&#xB4E4;&#xC911;&#xC5D0; &#xCCAB;&#xBC88;&#xC9F8; &#xBA85;&#xB839;&#xC774; PGID &#xC640; process group leader &#xAC00; &#xB429;&#xB2C8;&#xB2E4;. ( &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; &#xB0B4;&#xC5D0;&#xC11C; &#xC2E4;&#xD589;&#xB420; &#xACBD;&#xC6B0;&#xB294; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; PGID &#xB97C; &#xB530;&#xB985;&#xB2C8;&#xB2E4;.) &#xB2E4;&#xC74C;&#xC740; &#xD504;&#xB86C;&#xD504;&#xD2B8; &#xC0C1;&#xC5D0;&#xC11C; <code>cat | grep hello | wc -l</code> &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD55C; &#xC608;&#xC785;&#xB2C8;&#xB2E4;. &#xBAA8;&#xB450; bash shell PID &#xB97C; SID &#xB85C; &#xAC00;&#xC9C0;&#xACE0; &#xC788;&#xACE0; &#xD30C;&#xC774;&#xD504;&#xB85C; &#xC5F0;&#xACB0;&#xB41C; &#xBA85;&#xB839; &#xC911;&#xC5D0; &#xCCAB;&#xBC88;&#xC9F8; &#xBA85;&#xB839;&#xC758; PID &#xAC00; PGID &#xB85C; &#xC0AC;&#xC6A9;&#xB41C; &#xAC83;&#xC744; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<p><img src="images/sid_pgid_2.png" alt=""></p>
<p>&#xC774;&#xC640; &#xAC19;&#xC774; process group &#xC740; job control &#xC744;&#xD560;&#xB54C; &#xAE30;&#xBCF8;&#xB2E8;&#xC704; ( job ) &#xAC00; &#xB429;&#xB2C8;&#xB2E4;.
&#xD558;&#xB098;&#xC758; session &#xC5D0;&#xC11C;&#xB294; &#xD558;&#xB098;&#xC758; process group &#xB9CC; foreground &#xAC00; &#xB420;&#xC218;&#xC788;&#xACE0; &#xB098;&#xBA38;&#xC9C0;&#xB294; background &#xAC00; &#xB429;&#xB2C8;&#xB2E4;.</p>
<blockquote>
<p>&#xC2E4;&#xD589;&#xB418;&#xB294; &#xBAA8;&#xB4E0; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xADF8;&#xB8F9;&#xC5D0; &#xC18D;&#xD558;&#xAC8C; &#xB418;&#xACE0;, &#xB610;&#xD55C; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xADF8;&#xB8F9;&#xC740; &#xC138;&#xC158;&#xC5D0; &#xC18D;&#xD558;&#xAC8C; &#xB429;&#xB2C8;&#xB2E4;.</p>
</blockquote>
<h3 id="&#xC870;&#xD68C;&#xD558;&#xACE0;-&#xC2E0;&#xD638;&#xBCF4;&#xB0B4;&#xAE30;">&#xC870;&#xD68C;&#xD558;&#xACE0; &#xC2E0;&#xD638;&#xBCF4;&#xB0B4;&#xAE30;</h3>
<p>&#xD604;&#xC7AC; &#xC2E4;&#xD589;&#xB418;&#xACE0; &#xC788;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xB4E4;&#xC758; PPID, PID, PGID, SID &#xAD00;&#xACC4;&#xB294; &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774;  ps &#xBA85;&#xB839;&#xC744; &#xD1B5;&#xD574;
&#xC54C;&#xC544;&#xBCFC; &#xC218; &#xC788;&#xACE0; <code>pgrep</code> , <code>pkill</code> &#xBA85;&#xB839;&#xC744; &#xC0AC;&#xC6A9;&#xD558;&#xBA74;  process group &#xC774;&#xB098; session &#xBCC4;&#xB85C;
&#xC870;&#xD68C;&#xD558;&#xAC70;&#xB098; &#xC2DC;&#xADF8;&#xB110;&#xC744; &#xBCF4;&#xB0BC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;. </p>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xB2E4;&#xC74C; &#xBA85;&#xB839;&#xC744; &#xC774;&#xC6A9;&#xD558;&#xBA74; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; group id &#xC640; session id &#xC815;&#xBCF4;&#xB97C; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</span>
$ ps jf
$ ps fo user,ppid,pid,pgid,sid,<span class="hljs-built_in">stat</span>,comm

<span class="hljs-comment"># &#xD2B9;&#xC815; &#xBA85;&#xB839;&#xC758; &#xC774;&#xB984;&#xC744; &#xAC00;&#xC9C0;&#xACE0; PID &#xB97C; &#xAD6C;&#xD558;&#xB294; &#xBC29;&#xBC95;</span>
$ ps -C test.sh -o pid=
$ pgrep -x test.sh

<span class="hljs-comment"># &#xD2B9;&#xC815; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; PGID (Process Group ID) &#xC640; SID (Session ID) &#xB97C; &#xAD6C;&#xD558;&#xB294; &#xBC29;&#xBC95;</span>
$ ps -o pgid= <span class="hljs-number">1234</span>          <span class="hljs-comment"># PID &#xAC00; 1234 &#xC778; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; PGID &#xB97C; &#xCD9C;&#xB825;</span>
$ ps -o sid= <span class="hljs-number">1234</span>           <span class="hljs-comment"># PID &#xAC00; 1234 &#xC778; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; SID &#xB97C; &#xCD9C;&#xB825;</span>
$ ps -o pgid= -C test.sh    <span class="hljs-comment"># &#xBA85;&#xB839; &#xC774;&#xB984;&#xC774; test.sh &#xC778; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; PGID &#xB97C; &#xCD9C;&#xB825;</span>
$ ps -o sid= -C test.sh     <span class="hljs-comment"># &#xBA85;&#xB839; &#xC774;&#xB984;&#xC774; test.sh &#xC778; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; SID &#xB97C; &#xCD9C;&#xB825;</span>

<span class="hljs-comment"># &#xB2E4;&#xC74C;&#xC740; test.sh &#xBA85;&#xB839;&#xACFC; &#xAC19;&#xC740; PGID &#xB97C; &#xAC16;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC744; &#xBAA8;&#xB450; &#xCD9C;&#xB825;&#xD569;&#xB2C8;&#xB2E4;.</span>
$ ps -o pid= $(ps -o pgid= -C test.sh | sed <span class="hljs-string">&apos;s/^/-/&apos;</span>)
$ pgrep -g $(ps -o pgid= -C test.sh | paste -sd,)

<span class="hljs-comment"># &#xB2E4;&#xC74C;&#xC740; test.sh &#xBA85;&#xB839;&#xACFC; &#xAC19;&#xC740; SID &#xB97C; &#xAC16;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC744; &#xBAA8;&#xB450; &#xCD9C;&#xB825;&#xD569;&#xB2C8;&#xB2E4;.</span>
$ ps -o pid= $(ps -o sid= -C test.sh | sed <span class="hljs-string">&apos;s/^/+/&apos;</span>)
$ pgrep <span class="hljs-operator">-s</span> $(ps -o sid= -C test.sh | paste -sd,)
</code></pre>
<blockquote>
<p><code>ps</code> &#xBA85;&#xB839;&#xC5D0;&#xC11C;&#xB294; &#xC22B;&#xC790; &#xC55E;&#xC5D0; <code>-</code> &#xAC00; &#xBD99;&#xC73C;&#xBA74; PGID &#xAC00; &#xB418;&#xACE0; <code>+</code> &#xAC00; &#xBD99;&#xC73C;&#xBA74; SID &#xAC00; &#xB429;&#xB2C8;&#xB2E4;.</p>
</blockquote>
<h3 id="&#xC2E4;&#xD589;&#xC911;&#xC778;-&#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xB97C;-&#xC885;&#xB8CC;&#xD558;&#xB294;-&#xBC29;&#xBC95;">&#xC2E4;&#xD589;&#xC911;&#xC778; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xB97C; &#xC885;&#xB8CC;&#xD558;&#xB294; &#xBC29;&#xBC95;</h3>
<p>&#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xB97C; &#xC885;&#xB8CC;&#xD560; &#xB54C;&#xB294; jobspec &#xC744; &#xC774;&#xC6A9;&#xD558;&#xAC70;&#xB098; PGID &#xB97C; &#xC774;&#xC6A9;&#xD574; process group &#xC5D0; &#xC2E0;&#xD638;&#xB97C; &#xBCF4;&#xB0B4;&#xC57C; &#xD569;&#xB2C8;&#xB2E4;.
&#xB610;&#xB294; Ctrl-c &#xD0A4;&#xB97C; &#xB204;&#xB974;&#xB294; &#xAC83;&#xB3C4; process group &#xC5D0; &#xC2E0;&#xD638;&#xB97C; &#xBCF4;&#xB0B4;&#xB294; &#xBC29;&#xBC95; &#xC911;&#xC5D0; &#xD558;&#xB098;&#xC785;&#xB2C8;&#xB2E4;.
&#xADF8;&#xB807;&#xC9C0; &#xC54A;&#xACE0; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; PID &#xC5D0;&#xB9CC; &#xC2E0;&#xD638;&#xB97C; &#xBCF4;&#xB0B4;&#xAC8C; &#xB418;&#xBA74; child process &#xB294; &#xC885;&#xB8CC;&#xB418;&#xC9C0; &#xC54A;&#xACE0; &#xB0A8;&#xC544; &#xC788;&#xAC8C; &#xB429;&#xB2C8;&#xB2E4;.
&#xB2E4;&#xC74C;&#xC740; ping &#xC678;&#xBD80; &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD558;&#xACE0; &#xC788;&#xB294; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xC5D0; PID &#xB97C; &#xC774;&#xC6A9;&#xD574; &#xC885;&#xB8CC; &#xC2E0;&#xD638;&#xB97C; &#xBCF4;&#xB0B8; &#xACBD;&#xC6B0;&#xC778;&#xB370;
child process &#xC778; ping &#xBA85;&#xB839;&#xC740; &#xC885;&#xB8CC;&#xB418;&#xC9C0; &#xC54A;&#xC740; &#xCCB4; &#xB0A8;&#xC544; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">-------- test.sh --------
<span class="hljs-shebang">#!/bin/bash</span>
<span class="hljs-built_in">echo</span> test.sh ... start

ping <span class="hljs-number">0.0</span>.<span class="hljs-number">0.1</span>

<span class="hljs-built_in">echo</span> test.sh ... end
-------------------------

$ ./test.sh &amp;

<span class="hljs-comment"># test.sh &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; &#xC2E4;&#xD589;&#xD6C4; &#xAC19;&#xC740; PGID &#xB97C; &#xAC16;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xC870;&#xD68C;</span>
$ ps jf $(pgrep -g $(ps -o pgid= -C test.sh | head -n1))
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
 <span class="hljs-number">4655</span> <span class="hljs-number">18946</span> <span class="hljs-number">18946</span>  <span class="hljs-number">4655</span> pts/<span class="hljs-number">14</span>   <span class="hljs-number">19642</span> S     <span class="hljs-number">1000</span>   <span class="hljs-number">0</span>:<span class="hljs-number">00</span> /bin/bash ./test.sh
<span class="hljs-number">18946</span> <span class="hljs-number">18949</span> <span class="hljs-number">18946</span>  <span class="hljs-number">4655</span> pts/<span class="hljs-number">14</span>   <span class="hljs-number">19642</span> S     <span class="hljs-number">1000</span>   <span class="hljs-number">0</span>:<span class="hljs-number">00</span>  \_ ping <span class="hljs-number">0.0</span>.<span class="hljs-number">0.1</span>

<span class="hljs-comment"># test.sh &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; PID &#xB97C; &#xC774;&#xC6A9;&#xD574; &#xC885;&#xB8CC;</span>
$ <span class="hljs-built_in">kill</span> <span class="hljs-number">18946</span>

<span class="hljs-comment"># child process &#xC778; ping &#xBA85;&#xB839;&#xC740; &#xC885;&#xB8CC;&#xB418;&#xC9C0; &#xC54A;&#xACE0; PPID &#xAC00; init &#xC73C;&#xB85C; &#xBC14;&#xB00C;&#xC5B4; &#xB0A8;&#xC544;&#xC788;&#xB2E4;.</span>
$ ps j -C ping
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
    <span class="hljs-number">1</span> <span class="hljs-number">18949</span> <span class="hljs-number">18946</span>  <span class="hljs-number">4655</span> pts/<span class="hljs-number">14</span>   <span class="hljs-number">19688</span> S     <span class="hljs-number">1000</span>   <span class="hljs-number">0</span>:<span class="hljs-number">00</span> ping <span class="hljs-number">0.0</span>.<span class="hljs-number">0.1</span>
</code></pre>
<p>&#xB530;&#xB77C;&#xC11C; &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774; PGID &#xB97C; &#xC774;&#xC6A9;&#xD574; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xB97C; &#xC885;&#xB8CC;&#xD574;&#xC57C; &#xD569;&#xB2C8;&#xB2E4;.</p>
<ul>
<li>kill -- -1234 ( PGID &#xC55E;&#xC5D0; <code>-</code> &#xBB38;&#xC790;&#xB97C; &#xBD99;&#xC778;&#xB2E4;. )</li>
<li>pkill -g 1234</li>
</ul>
<pre><code class="lang-bash">$ test.sh &amp;

$ ps j -C test.sh
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
<span class="hljs-number">23973</span> <span class="hljs-number">25517</span> <span class="hljs-number">25517</span> <span class="hljs-number">23973</span> pts/<span class="hljs-number">16</span>   <span class="hljs-number">25517</span> S+    <span class="hljs-number">1000</span>   <span class="hljs-number">0</span>:<span class="hljs-number">00</span> /bin/bash ./test.sh

<span class="hljs-comment"># test.sh &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8; PGID &#xB97C; &#xC774;&#xC6A9;&#xD574; &#xC885;&#xB8CC;</span>
$ <span class="hljs-built_in">kill</span> -- -<span class="hljs-number">25517</span>

<span class="hljs-comment"># &#xAC19;&#xC740; PGID &#xB97C; &#xAC16;&#xB294; ping &#xBA85;&#xB839;&#xB3C4; &#xD568;&#xAED8; &#xC885;&#xB8CC;&#xB418;&#xC5C8;&#xB2E4;.</span>
$ ps j -C ping
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
</code></pre>
<h4 id="session-&#xC774;-&#xC885;&#xB8CC;&#xB420;&#xB54C;-&#xAC19;&#xC740;-session-id-&#xB97C;-&#xAC16;&#xB294;&#xB2E4;&#xACE0;-&#xBAA8;&#xB450;-&#xC885;&#xB8CC;&#xB418;&#xB294;&#xAC83;&#xC740;-&#xC544;&#xB2C8;&#xB2E4;">Session &#xC774; &#xC885;&#xB8CC;&#xB420;&#xB54C; &#xAC19;&#xC740; Session ID &#xB97C; &#xAC16;&#xB294;&#xB2E4;&#xACE0; &#xBAA8;&#xB450; &#xC885;&#xB8CC;&#xB418;&#xB294;&#xAC83;&#xC740; &#xC544;&#xB2C8;&#xB2E4;.</h4>
<p>&#xAC00;&#xB839; fork() &#xC5D0;&#xC758;&#xD574; &#xBD80;&#xBAA8; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xBA3C;&#xC800; &#xC885;&#xB8CC;&#xD558;&#xC5EC; child process &#xC758;
&#xBD80;&#xBAA8;&#xAC00; init &#xC774;&#xB098; systemd &#xB85C; reparent &#xB420;&#xACBD;&#xC6B0; &#xAC19;&#xC740; session id &#xB97C; &#xAC16;&#xACE0; &#xC788;&#xC5B4;&#xB3C4;
child process &#xB294; &#xC885;&#xB8CC;&#xB418;&#xC9C0; &#xC54A;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<p><a name="setsid"></a></p>
<h3 id="&#xC0C8;&#xB85C;&#xC6B4;-session-id-&#xB85C;-&#xC2E4;&#xD589;&#xD558;&#xAE30;">&#xC0C8;&#xB85C;&#xC6B4; session id &#xB85C; &#xC2E4;&#xD589;&#xD558;&#xAE30;</h3>
<p>&#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xB97C; background &#xB85C; &#xC2E4;&#xD589;&#xC2DC;&#xD0AC;&#xB54C; <code>setsid</code> &#xBA85;&#xB839;&#xC744; &#xC774;&#xC6A9;&#xD558;&#xBA74; &#xC0C8;&#xB85C;&#xC6B4; SID, PGID &#xAC00; &#xD560;&#xB2F9;&#xB418;&#xACE0; PPID &#xB3C4; init &#xC73C;&#xB85C; &#xBC14;&#xB00C;&#xC5B4; &#xC2E4;&#xD589;&#xB429;&#xB2C8;&#xB2E4;. 
SID &#xAC00; &#xBC14;&#xB00C;&#xBBC0;&#xB85C; &#xAE30;&#xC874;&#xC758; controlling terminal &#xC5D0;&#xC11C; &#xB5A8;&#xC5B4;&#xC838; &#xB098;&#xAC00; HUP, INT &#xAC19;&#xC740; &#xC2E0;&#xD638;&#xB3C4; &#xC804;&#xB2EC;&#xB418;&#xC9C0; &#xC54A;&#xAC8C; &#xB429;&#xB2C8;&#xB2E4;.
&#xADF8;&#xB9AC;&#xACE0; controlling terminal &#xC5D0; &#xD574;&#xB2F9;&#xD558;&#xB294; /dev/tty &#xB3C4; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;.
parent &#xB3C4; init &#xC774; &#xB418;&#xBBC0;&#xB85C; &#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xB97C; daemon &#xC73C;&#xB85C; &#xC2E4;&#xD589;&#xC2DC;&#xD0A4;&#xB294; &#xD6A8;&#xACFC;&#xB97C; &#xAC16;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ cat test.sh 
<span class="hljs-shebang">#!/bin/bash
</span>
<span class="hljs-built_in">echo</span> start .....
ls <span class="hljs-operator">-l</span> /dev/fd/ &gt; /dev/tty    <span class="hljs-comment"># controlling terminal &#xB85C; &#xCD9C;&#xB825;</span>
<span class="hljs-built_in">echo</span> end .....

$ ./test.sh          
start .....
total <span class="hljs-number">0</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> Mar <span class="hljs-number">13</span> <span class="hljs-number">23</span>:<span class="hljs-number">54</span> <span class="hljs-number">0</span> -&gt; /dev/pts/<span class="hljs-number">15</span>
l-wx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> Mar <span class="hljs-number">13</span> <span class="hljs-number">23</span>:<span class="hljs-number">54</span> <span class="hljs-number">1</span> -&gt; /dev/tty
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> Mar <span class="hljs-number">13</span> <span class="hljs-number">23</span>:<span class="hljs-number">54</span> <span class="hljs-number">2</span> -&gt; /dev/pts/<span class="hljs-number">15</span>
lr-x------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> Mar <span class="hljs-number">13</span> <span class="hljs-number">23</span>:<span class="hljs-number">54</span> <span class="hljs-number">3</span> -&gt; /proc/<span class="hljs-number">15343</span>/fd
end .....

<span class="hljs-comment"># controlling terminal &#xC744; &#xAC16;&#xC9C0; &#xC54A;&#xAC8C;&#xB418;&#xC5B4; /dev/tty &#xB97C; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC5C6;&#xB2E4;.</span>
$ setsid ./test.sh 
start .....
./test.sh: line <span class="hljs-number">5</span>: /dev/tty: No such device or address
end .....
</code></pre>
<p><strong> daemon &#xB9CC;&#xB4DC;&#xB294; &#xBC29;&#xBC95; </strong></p>
<pre><code class="lang-bash">$ setsid daemon.sh &gt; /dev/null <span class="hljs-number">2</span>&gt;&amp;<span class="hljs-number">1</span> &lt; /dev/null
</code></pre>
<h3 id="pgid-&#xB97C;-&#xBCC0;&#xACBD;&#xD558;&#xC5EC;-child-process-&#xC2E4;&#xD589;">PGID &#xB97C; &#xBCC0;&#xACBD;&#xD558;&#xC5EC; child process &#xC2E4;&#xD589;</h3>
<p>&#xC2A4;&#xD06C;&#xB9BD;&#xD2B8;&#xB97C; a.sh -&gt; b.sh -&gt; c.sh -&gt; d.sh  &#xC21C;&#xC11C;&#xB85C; &#xC2E4;&#xD589;&#xD558;&#xC5EC; &#xD604;&#xC7AC; sleep &#xC0C1;&#xD0DC;&#xC5D0; &#xC788;&#xB2E4;&#xBA74;
Ctrl-c &#xB97C; &#xB204;&#xB97C;&#xACBD;&#xC6B0; <a href="tty.html#tty_driver">tty driver</a> &#xC5D0; &#xC758;&#xD574; 
INT &#xC2E0;&#xD638;&#xAC00; foreground process group &#xC5D0; &#xC804;&#xB2EC;&#xB418;&#xC5B4;  4&#xAC1C;&#xC758; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB294; &#xBAA8;&#xB450; &#xC885;&#xB8CC;&#xD558;&#xAC8C; &#xB429;&#xB2C8;&#xB2E4;.
&#xC774;&#xB54C; &#xB9CC;&#xC57D;&#xC5D0; c.sh &#xC5D0;&#xC11C; d.sh &#xC744; &#xC2E4;&#xD589;&#xD560;&#xB54C; PGID &#xB97C; &#xBCC0;&#xACBD;&#xD560;&#xC218; &#xC788;&#xB2E4;&#xBA74; 
c.sh &#xACFC; d.sh &#xAE4C;&#xC9C0;&#xB9CC; &#xC885;&#xB8CC;&#xD558;&#xACE0; a.sh, b.sh &#xC740; &#xB098;&#xBA38;&#xC9C0; &#xBA85;&#xB839;&#xC774; &#xC2E4;&#xD589;&#xB418;&#xAC8C; &#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<p>shell &#xC5D0;&#xC11C;&#xB294; setsid &#xC678;&#xBD80; &#xBA85;&#xB839;&#xC744; &#xC0AC;&#xC6A9;&#xD558;&#xC5EC; SID, PGID &#xB97C; &#xBCC0;&#xACBD;&#xD574; &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD560;&#xC218; &#xC788;&#xC9C0;&#xB9CC;
setpgid &#xAC19;&#xC740; &#xBA85;&#xB839;&#xC740; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xD558;&#xC9C0;&#xB9CC; &#xAC04;&#xC811;&#xC801;&#xC73C;&#xB85C; <code>set -o monitor</code> &#xC635;&#xC158; &#xC124;&#xC815;&#xC744; &#xD1B5;&#xD574;&#xC11C; &#xC774;&#xD6C4;&#xC5D0; &#xC2E4;&#xD589;&#xB418;&#xB294; &#xBA85;&#xB839;&#xC774;
&#xB2E4;&#xB978; PGID &#xB97C; &#xAC16;&#xAC8C; &#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ cat a.sh           $ cat b.sh           $ cat c.sh           $ cat d.sh
<span class="hljs-shebang">#!/bin/bash          #!/bin/bash          #!/bin/bash          #!/bin/bash
</span>
<span class="hljs-built_in">echo</span> start a.sh      <span class="hljs-built_in">echo</span> start b.sh      <span class="hljs-built_in">echo</span> start c.sh      <span class="hljs-built_in">echo</span> start d.sh

./b.sh               ./c.sh               ./d.sh               cat

<span class="hljs-built_in">echo</span> end a.sh        <span class="hljs-built_in">echo</span> end b.sh        <span class="hljs-built_in">echo</span> end c.sh        <span class="hljs-built_in">echo</span> end d.sh


<span class="hljs-comment"># d.sh &#xC5D0;&#xC11C; cat &#xBA85;&#xB839;&#xC5D0; &#xC758;&#xD574; &#xBE14;&#xB85D;&#xB410;&#xC744;&#xB54C; ctrl-c &#xB97C; &#xC785;&#xB825;&#xD558;&#xBA74; </span>
<span class="hljs-comment"># &#xAC19;&#xC740; PGID &#xB97C; &#xAC16;&#xB294; a.sh b.sh c.sh d.sh &#xC774; &#xBAA8;&#xB450; &#xC885;&#xB8CC;&#xB41C;&#xB2E4;.</span>
$ ./a.sh 
start a.sh
start b.sh
start c.sh
start d.sh
^C              <span class="hljs-comment"># &#xBAA8;&#xB450; &#xC885;&#xB8CC;&#xB41C;&#xB2E4;.</span>
</code></pre>
<p>&#xC774;&#xBC88;&#xC5D0;&#xB294; <code>c.sh</code> &#xC5D0; <code>set -o monitor</code> &#xC635;&#xC158;&#xC744; &#xCD94;&#xAC00;</p>
<pre><code class="lang-bash">$ cat c.sh                    $ ./a.sh 
<span class="hljs-shebang">#!/bin/bash                   start a.sh</span>
                              start b.sh
<span class="hljs-built_in">echo</span> start c.sh               start c.sh
                              start d.sh
<span class="hljs-built_in">set</span> -o monitor                ^Cend b.sh     <span class="hljs-comment"># ctrl-c &#xB97C; &#xC785;&#xB825;&#xD558;&#xBA74; c.sh d.sh &#xB9CC; &#xC885;&#xB8CC;&#xAC00; &#xB418;&#xACE0;</span>
./d.sh                        end a.sh       <span class="hljs-comment"># b.sh a.sh &#xC740; &#xB098;&#xBA38;&#xC9C0; &#xBA85;&#xB839;&#xB4E4;&#xC774; &#xC2E4;&#xD589;&#xB41C;&#xB2E4;.</span>

<span class="hljs-built_in">echo</span> end c.sh
</code></pre>
<p><img src="images/change_pgid.png" alt=""></p>
<h1 id="quiz">Quiz</h1>
<p><code>ps axj</code> &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD574; &#xBCF4;&#xBA74; &#xB9E8; &#xC704;&#xC5D0;&#xC11C; &#xB2E4;&#xC74C; &#xB450; &#xD56D;&#xBAA9;&#xC744; &#xCC3E;&#xC744; &#xC218; &#xC788;&#xB294;&#xB370;&#xC694;.
&#xD558;&#xB098;&#xB294; &#xC2DC;&#xC2A4;&#xD15C;&#xC758; &#xC2DC;&#xC791;&#xACFC; &#xC885;&#xB8CC;, &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xC0DD;&#xC131;, &#xBAA8;&#xB2C8;&#xD130;&#xB9C1;&#xC5D0; &#xAD00;&#xACC4;&#xB41C; init &#xC774;&#xACE0;
&#xB2E4;&#xB978; &#xD558;&#xB098;&#xB294; kernel thread &#xB97C; &#xC0DD;&#xC131;&#xD558;&#xB294; kthreadd &#xC785;&#xB2C8;&#xB2E4;.
&#xADF8;&#xB7F0;&#xB370; &#xBAA8;&#xB450; PPID &#xAC00; 0 &#xBC88;&#xC778; &#xAC83;&#xC744; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
PID 0 &#xC740; &#xC5B4;&#xB5A4; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC77C;&#xAE4C;&#xC694;?</p>
<p><img src="images/pid_0.png" alt=""></p>
<p>kernel &#xCD08;&#xAE30;&#xD654; &#xB2E8;&#xACC4;&#xC5D0;&#xC11C; &#xC2E4;&#xD589;&#xB418;&#xB294; startup function &#xC744; swapper &#xB610;&#xB294; process 0 &#xC73C;&#xB85C; &#xBD80;&#xB985;&#xB2C8;&#xB2E4;.
&#xC5EC;&#xAE30;&#xC11C;&#xB294; paging &#xAD00;&#xB828; &#xBA54;&#xBAA8;&#xB9AC; &#xC124;&#xC815;, interrupt handling &#xC124;&#xC815;, &#xCEE4;&#xB110;&#xC5D0;&#xC11C; &#xC0AC;&#xC6A9;&#xD558;&#xB294;
&#xAD6C;&#xC870;&#xCCB4; &#xC124;&#xC815; &#xB4F1; &#xC5EC;&#xB7EC; &#xAC00;&#xC9C0; &#xCD08;&#xAE30;&#xD654; &#xC791;&#xC5C5;&#xC744; &#xD558;&#xACE0; &#xCCAB; &#xBC88;&#xC9F8; user space &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC778; PID 1 &#xBC88; init &#xACFC;
kernel space &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC778; PID 2 &#xBC88; kthreadd &#xC744; &#xC0DD;&#xC131;&#xD569;&#xB2C8;&#xB2E4;.
&#xC774;&#xD6C4;&#xC5D0;&#xB294; idle &#xC0C1;&#xD0DC;&#xAC00; &#xB418;&#xC5B4;&#xC11C; &#xC2DC;&#xC2A4;&#xD15C; &#xB0B4;&#xC5D0; running &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xC5C6;&#xC744; &#xACBD;&#xC6B0; &#xBC18;&#xBCF5;&#xC801;&#xC73C;&#xB85C; hlt &#xC5B4;&#xC148;&#xBE14;&#xB9AC; &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD569;&#xB2C8;&#xB2E4;.
init &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB294; &#xC6D0;&#xB798; &#xCEE4;&#xB110; &#xC2A4;&#xB808;&#xB4DC;&#xC600;&#xB294;&#xB370; &#xC774;&#xD6C4;&#xC5D0; exec() &#xC2DC;&#xC2A4;&#xD15C;&#xCF5C;&#xC744; &#xC2E4;&#xD589;&#xD558;&#xC5EC;
user space &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xB418;&#xC5B4; &#xC774;&#xB984;&#xC5D0; <code>[ ]</code> &#xAC00; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<p>&#xB530;&#xB77C;&#xC11C; &#xBAA8;&#xB4E0; user space &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB294; init &#xC758; &#xC790;&#xC190; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xB418;&#xACE0;,
&#xBAA8;&#xB4E0; kernel space &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB294; kthreadd &#xC758; &#xC790;&#xC190; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xB429;&#xB2C8;&#xB2E4;.</p>
<blockquote>
<p>idle &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB3C4; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC774;&#xBBC0;&#xB85C; &#xC2DC;&#xC2A4;&#xD15C;&#xC5D0;&#xB294; &#xD56D;&#xC0C1; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xC874;&#xC7AC;&#xD558;&#xB294; &#xAC83;&#xACFC; &#xAC19;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
</blockquote>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xC2DC;&#xC2A4;&#xD15C; &#xB0B4;&#xC758; &#xBAA8;&#xB4E0; kernel space &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB97C; &#xCD9C;&#xB825;&#xD558;&#xB824;&#xBA74; PPID &#xAC00; 2 &#xBC88;&#xC778; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB97C; &#xCD9C;&#xB825;&#xD558;&#xBA74; &#xB41C;&#xB2E4;.</span>
$ ps f --ppid <span class="hljs-number">2</span> <span class="hljs-number">2</span> 
  PID TTY      STAT   TIME COMMAND
    <span class="hljs-number">2</span> ?        S      <span class="hljs-number">0</span>:<span class="hljs-number">00</span> [kthreadd]
    <span class="hljs-number">3</span> ?        I&lt;     <span class="hljs-number">0</span>:<span class="hljs-number">00</span>  \_ [rcu_gp]
    <span class="hljs-number">4</span> ?        I&lt;     <span class="hljs-number">0</span>:<span class="hljs-number">00</span>  \_ [rcu_par_gp]
    <span class="hljs-number">8</span> ?        I&lt;     <span class="hljs-number">0</span>:<span class="hljs-number">00</span>  \_ [mm_percpu_wq]
    <span class="hljs-number">9</span> ?        S      <span class="hljs-number">0</span>:<span class="hljs-number">48</span>  \_ [ksoftirqd/<span class="hljs-number">0</span>]
   <span class="hljs-number">10</span> ?        I     <span class="hljs-number">20</span>:<span class="hljs-number">53</span>  \_ [rcu_<span class="hljs-built_in">sched</span>]
   <span class="hljs-number">11</span> ?        S      <span class="hljs-number">0</span>:<span class="hljs-number">06</span>  \_ [migration/<span class="hljs-number">0</span>]
   <span class="hljs-number">12</span> ?        S      <span class="hljs-number">0</span>:<span class="hljs-number">00</span>  \_ [idle_inject/<span class="hljs-number">0</span>]
   <span class="hljs-number">14</span> ?        S      <span class="hljs-number">0</span>:<span class="hljs-number">00</span>  \_ [cpuhp/<span class="hljs-number">0</span>]
   <span class="hljs-number">15</span> ?        S      <span class="hljs-number">0</span>:<span class="hljs-number">00</span>  \_ [cpuhp/<span class="hljs-number">1</span>]
   . . . .
   . . . .
<span class="hljs-comment"># kernel space &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB97C; &#xC81C;&#xC678;&#xD558;&#xACE0; ( --deselect ) &#xCD9C;&#xB825;&#xD558;&#xBA74; &#xBAA8;&#xB4E0; user space &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xB41C;&#xB2E4;.   </span>
$ ps f --deselect --ppid <span class="hljs-number">2</span> <span class="hljs-number">2</span>
</code></pre>
<hr>
<p>&#xCEE4;&#xB110;&#xC758; &#xACBD;&#xC6B0; &#xD558;&#xB4DC;&#xC6E8;&#xC5B4; &#xC778;&#xD130;&#xB7FD;&#xD2B8;&#xAC00; &#xBC1C;&#xC0DD;&#xD558;&#xAC70;&#xB098;, system call, exception &#xC774; &#xBC1C;&#xC0DD;&#xD588;&#xC744;&#xB54C;
&#xD604;&#xC7AC; &#xC2E4;&#xD589; &#xC911;&#xC778; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xC911;&#xB2E8;&#xB41C; &#xC0C1;&#xD0DC;&#xC5D0;&#xC11C; kernel mode &#xB85C; &#xC9C4;&#xC785;&#xD558;&#xC5EC; &#xC2E4;&#xD589;&#xB418;&#xB294; &#xD615;&#xD0DC;&#xC774;&#xBBC0;&#xB85C;
&#xB530;&#xB85C; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB77C;&#xB294; &#xAC1C;&#xB150;&#xC774; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;( &#xCEE4;&#xB110; &#xC2A4;&#xB808;&#xB4DC;&#xB294; &#xC81C;&#xC678; ).
&#xC544;&#xB798; &#xADF8;&#xB9BC;&#xC740; &#xC2E4;&#xC81C; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xC8FC;&#xC18C;&#xACF5;&#xAC04;&#xC744; (virtual address space) &#xB098;&#xD0C0;&#xB0B4;&#xB294;&#xB370;&#xC694;.
&#xCEE4;&#xB110; &#xCF54;&#xB4DC;&#xC640; &#xB370;&#xC774;&#xD130;&#xAC00; &#xC704;&#xCE58;&#xD55C; &#xCEE4;&#xB110; &#xCABD; &#xC8FC;&#xC18C;&#xB294; shared library &#xCC98;&#xB7FC; &#xBAA8;&#xB4E0; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC5D0;&#xC11C; &#xACF5;&#xC720;&#xB418;&#xBBC0;&#xB85C;
&#xC2A4;&#xCF00;&#xC904;&#xB7EC;&#xC5D0; &#xC758;&#xD574; &#xB2E4;&#xB978; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB85C; &#xC2A4;&#xC704;&#xCE6D;&#xC774; &#xB418;&#xC5B4;&#xB3C4; &#xD56D;&#xC0C1; &#xC2E4;&#xD589;&#xB420; &#xC218;&#xAC00; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xB610;&#xD55C; user mode &#xC5D0;&#xC11C; &#xC811;&#xADFC;&#xD560; &#xACBD;&#xC6B0; page fault &#xAC00; &#xBC1C;&#xC0DD;&#xD558;&#xBBC0;&#xB85C; &#xC811;&#xADFC;&#xD560; &#xC218;&#xAC00; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<p><img src="images/system_address_space.png" alt=""></p>
<p><img src="images/virtual_memory.png" alt=""></p>
<h1 id="quiz">Quiz</h1>
<p>&#xD30C;&#xC774;&#xD504;&#xB97C; &#xC774;&#xC6A9;&#xD574; &#xBA85;&#xB839;&#xB4E4;&#xC744; &#xC5F0;&#xACB0;&#xD574;&#xC11C; &#xC2E4;&#xD589;&#xD558;&#xBA74; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xADF8;&#xB8F9;&#xC774; &#xC0DD;&#xC131;&#xB418;&#xACE0; Ctrl-c &#xB97C;
&#xC785;&#xB825;&#xD558;&#xAC8C; &#xB418;&#xBA74; &#xD574;&#xB2F9; &#xADF8;&#xB8F9;&#xC5D0; &#xC18D;&#xD55C; &#xBAA8;&#xB4E0; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC5D0; SIGINT &#xC2E0;&#xD638;&#xAC00; &#xC804;&#xB2EC;&#xB418;&#xC5B4; &#xC885;&#xB8CC;&#xD558;&#xAC8C; &#xB429;&#xB2C8;&#xB2E4;.
&#xC2E4;&#xC81C; &#xC2E0;&#xD638;&#xAC00; &#xC804;&#xB2EC;&#xB418;&#xB294; &#xAC83;&#xC744; C &#xC5B8;&#xC5B4;&#xB85C; &#xC791;&#xC131;&#xD574; &#xD655;&#xC778;&#xD574; &#xBCF4;&#xB294; &#xAC83;&#xC785;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-c">$ cat test.c

<span class="hljs-preprocessor">#<span class="hljs-keyword">include</span> <span class="hljs-string">&lt;stdio.h&gt;</span></span>
<span class="hljs-preprocessor">#<span class="hljs-keyword">include</span> <span class="hljs-string">&lt;signal.h&gt;</span></span>
<span class="hljs-preprocessor">#<span class="hljs-keyword">include</span> <span class="hljs-string">&lt;stdlib.h&gt;</span></span>
<span class="hljs-preprocessor">#<span class="hljs-keyword">include</span> <span class="hljs-string">&lt;unistd.h&gt;</span></span>

<span class="hljs-function"><span class="hljs-keyword">void</span> <span class="hljs-title">signal_handler</span><span class="hljs-params">(<span class="hljs-keyword">int</span> sig)</span> </span>{
    <span class="hljs-keyword">switch</span> (sig) {
        <span class="hljs-keyword">case</span> SIGINT:
            <span class="hljs-built_in">printf</span>(<span class="hljs-string">&quot;\n&gt;&gt;&gt; %d: received %d (SIGINT).\n&quot;</span>, getpid(), sig);
            <span class="hljs-keyword">break</span>;
        <span class="hljs-keyword">case</span> SIGQUIT:
            <span class="hljs-built_in">printf</span>(<span class="hljs-string">&quot;\n&gt;&gt;&gt; %d: received %d (SIGQUIT).\n&quot;</span>, getpid(), sig);
            <span class="hljs-built_in">exit</span>(sig);
    }
}

<span class="hljs-function"><span class="hljs-keyword">int</span> <span class="hljs-title">main</span><span class="hljs-params">()</span> 
</span>{
    signal(SIGINT, signal_handler);    <span class="hljs-comment">// Ctrl-c</span>
    signal(SIGQUIT, signal_handler);   <span class="hljs-comment">// Ctrl-\</span>

    <span class="hljs-keyword">while</span> (<span class="hljs-number">1</span>) {
        <span class="hljs-built_in">printf</span>(<span class="hljs-string">&quot;%d: working...\n&quot;</span>, getpid());
        sleep(<span class="hljs-number">1</span>);
    }
}
</code></pre>
<pre><code class="lang-sh">$ gcc test.c

$ ./a.out &gt;&amp;<span class="hljs-number">2</span> | ./a.out &gt;&amp;<span class="hljs-number">2</span> | ./a.out 
<span class="hljs-number">264649</span>: working...
<span class="hljs-number">264650</span>: working...
<span class="hljs-number">264648</span>: working...
<span class="hljs-number">264649</span>: working...
<span class="hljs-number">264650</span>: working...
<span class="hljs-number">264648</span>: working...
^C
&gt;&gt;&gt; <span class="hljs-number">264649</span>: received <span class="hljs-number">2</span> (SIGINT).

&gt;&gt;&gt; <span class="hljs-number">264650</span>: received <span class="hljs-number">2</span> (SIGINT).
<span class="hljs-number">264649</span>: working...

&gt;&gt;&gt; <span class="hljs-number">264648</span>: received <span class="hljs-number">2</span> (SIGINT).
<span class="hljs-number">264650</span>: working...
<span class="hljs-number">264648</span>: working...
<span class="hljs-number">264649</span>: working...
<span class="hljs-number">264650</span>: working...
<span class="hljs-number">264648</span>: working...
^C
&gt;&gt;&gt; <span class="hljs-number">264648</span>: received <span class="hljs-number">2</span> (SIGINT).
<span class="hljs-number">264648</span>: working...

&gt;&gt;&gt; <span class="hljs-number">264649</span>: received <span class="hljs-number">2</span> (SIGINT).

&gt;&gt;&gt; <span class="hljs-number">264650</span>: received <span class="hljs-number">2</span> (SIGINT).
<span class="hljs-number">264649</span>: working...
<span class="hljs-number">264650</span>: working...
<span class="hljs-number">264648</span>: working...
<span class="hljs-number">264649</span>: working...
<span class="hljs-number">264650</span>: working...
^\
&gt;&gt;&gt; <span class="hljs-number">264650</span>: received <span class="hljs-number">3</span> (SIGQUIT).

&gt;&gt;&gt; <span class="hljs-number">264649</span>: received <span class="hljs-number">3</span> (SIGQUIT).

&gt;&gt;&gt; <span class="hljs-number">264648</span>: received <span class="hljs-number">3</span> (SIGQUIT).
</code></pre>
<h1 id="2">2.</h1>
<p>&#xB2E4;&#xC74C;&#xC740; &#xD130;&#xBBF8;&#xB110;&#xC744; &#xB450;&#xAC1C; &#xC5F4;&#xC5B4;&#xC11C; &#xD55C;&#xCABD;&#xC5D0;&#xC11C;&#xB294; date &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD558;&#xACE0; &#xD55C;&#xCABD;&#xC5D0;&#xC11C;&#xB294;
sh &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB97C; strace &#xD558;&#xB824;&#xACE0; &#xD55C;&#xAC83;&#xC778;&#xB370;&#xC694;.
&#xADF8;&#xB7F0;&#xB370; &#xC2E4;&#xD589;&#xC744; &#xD574;&#xBCF4;&#xBA74; timeout &#xC5D0;&#xC758;&#xD574; strace &#xBA85;&#xB839;&#xC774; &#xC885;&#xB8CC;&#xB420; &#xB54C; vi &#xBA85;&#xB839;&#xB3C4; &#xD568;&#xAED8;
&#xC885;&#xB8CC;&#xAC00; &#xB418;&#xC5B4; &#xC81C;&#xB300;&#xB85C; &#xACB0;&#xACFC;&#xB97C; &#xC5BB;&#xC744; &#xC218;&#xAC00; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xC5B4;&#xB5BB;&#xAC8C; &#xD558;&#xBA74; vi &#xBA85;&#xB839;&#xC740; &#xD568;&#xAED8; &#xC885;&#xB8CC;&#xB418;&#xC9C0; &#xC54A;&#xAC8C; &#xD560; &#xC218; &#xC788;&#xC744;&#xAE4C;&#xC694;?</p>
<blockquote>
<p>&#xC544;&#xB798; &#xBA85;&#xB839; &#xC0AC;&#xC6A9; &#xB3D9;&#xC601;&#xC0C1;&#xC740; <a href="command_aliases.html#alias_example">&#xC5EC;&#xAE30;</a> (&#xD6C4;&#xBC18;&#xBD80;) &#xC5D0;&#xC11C; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
</blockquote>
<pre><code class="lang-bash"><span class="hljs-comment"># terminal 1</span>
$ timeout <span class="hljs-number">10</span> strace <span class="hljs-operator">-f</span> -p <span class="hljs-number">1234</span> |&amp; vi -    <span class="hljs-comment"># terminal 2 &#xC758; sh &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB97C; strace</span>

<span class="hljs-comment"># terminal 2</span>
sh$ <span class="hljs-built_in">echo</span> $$
<span class="hljs-number">1234</span>
sh$ date; date; date
</code></pre>
<p>&#xC774;&#xC640; &#xAC19;&#xC740; &#xACB0;&#xACFC;&#xAC00; &#xC0DD;&#xAE30;&#xB294; &#xC774;&#xC720;&#xB294; &#xD30C;&#xC774;&#xD504;&#xB85C; &#xC5F0;&#xACB0;&#xB41C; &#xBA85;&#xB839;&#xB4E4;&#xC740; &#xC2E4;&#xD589;&#xB420; &#xB54C; &#xAC19;&#xC740; process group &#xC744;
&#xD615;&#xC131;&#xD558;&#xAE30; &#xB54C;&#xBB38;&#xC785;&#xB2C8;&#xB2E4;.
timeout &#xC5D0;&#xC758;&#xD574; &#xC885;&#xB8CC; &#xC2E0;&#xD638;&#xAC00; &#xC804;&#xB2EC;&#xB420; &#xB54C;&#xB294; PGID &#xB97C; &#xC774;&#xC6A9;&#xD574; process group &#xC5D0; &#xC804;&#xB2EC;&#xB418;&#xBBC0;&#xB85C; 
&#xAC19;&#xC740; &#xADF8;&#xB8F9;&#xC5D0; &#xC18D;&#xD558;&#xB294; vi &#xBA85;&#xB839;&#xB3C4; &#xD568;&#xAED8; &#xC885;&#xB8CC;&#xAC00; &#xB429;&#xB2C8;&#xB2E4;.
&#xB530;&#xB77C;&#xC11C; &#xC774;&#xB54C;&#xB294; <code>{ ;}</code> &#xB97C; &#xC774;&#xC6A9;&#xD558;&#xC5EC; process group &#xC744; &#xBD84;&#xB9AC;&#xD574; &#xC8FC;&#xC5B4;&#xC57C; &#xD569;&#xB2C8;&#xB2E4;.</p>
<blockquote>
<p>&#xBCF4;&#xD1B5; <code>{ ;}</code> &#xC744; &#xC774;&#xC6A9;&#xD574; &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD574;&#xB3C4; &#xAC19;&#xC740; process group &#xC744; &#xAC16;&#xAC8C; &#xB418;&#xC9C0;&#xB9CC;
bash &#xC5D0;&#xC11C;&#xB294; timeout &#xBA85;&#xB839;&#xC774; &#xC2E4;&#xD589;&#xB420; &#xB54C; process group &#xC774; &#xBD84;&#xB9AC;&#xB429;&#xB2C8;&#xB2E4;.
( <code>sh</code> &#xC5D0;&#xC11C;&#xB294; &#xBD84;&#xB9AC;&#xB418;&#xC9C0; &#xC54A;&#xC74C; )</p>
</blockquote>
<pre><code class="lang-bash"><span class="hljs-comment"># PGID &#xAC00; &#xAC19;&#xC544;&#xC11C; timeout &#xC5D0;&#xC758;&#xD574; strace &#xBA85;&#xB839;&#xC774; &#xC885;&#xB8CC;&#xB420; &#xB54C; vi &#xB3C4; &#xD568;&#xAED8; &#xC885;&#xB8CC;&#xB41C;&#xB2E4;.</span>
$ timeout <span class="hljs-number">10</span> strace <span class="hljs-operator">-f</span> -p <span class="hljs-number">1234</span> |&amp; vi -
</code></pre>
<p><img src="images/subshell_op1.png" alt=""></p>
<pre><code class="lang-bash"><span class="hljs-comment"># { ;} &#xB97C; &#xC774;&#xC6A9;&#xD558;&#xBA74; subshell &#xC774; &#xC0DD;&#xC131;&#xB418;&#xACE0; process group &#xC774; &#xBD84;&#xB9AC;&#xB41C;&#xB2E4;.</span>
$ { timeout <span class="hljs-number">10</span> strace <span class="hljs-operator">-f</span> -p <span class="hljs-number">1234</span> ;} |&amp; vi -
</code></pre>
<p><img src="images/subshell_op2.png" alt=""></p>
<p><code>sh</code> &#xC5D0;&#xC11C;&#xB294; &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774; setsid &#xBA85;&#xB839;&#xC744; &#xC0AC;&#xC6A9;&#xD558;&#xBA74; &#xAC00;&#xB2A5;&#xD569;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ setsid timeout <span class="hljs-number">10</span> strace <span class="hljs-operator">-f</span> -p <span class="hljs-number">1234</span> <span class="hljs-number">2</span>&gt;&amp;<span class="hljs-number">1</span> | vi -
</code></pre>

                    
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