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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><link href=https://flokoe.github.io/bash-hackers-wiki/commands/builtin/exec/ rel=canonical><link href=../eval/ rel=prev><link href=../exit/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.5.44"><title>The exec builtin command - The Bash Hackers Wiki</title><link rel=stylesheet href=../../../assets/stylesheets/main.0253249f.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.06af60db.min.css><link rel=preconnect href=https://fonts.gstatic.com crossorigin><link rel=stylesheet href="https://fonts.googleapis.com/css?family=Roboto:300,300i,400,400i,700,700i%7CRoboto+Mono:400,400i,700,700i&display=fallback"><style>:root{--md-text-font:"Roboto";--md-code-font:"Roboto Mono"}</style><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#the-exec-builtin-command class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="The Bash Hackers Wiki" class="md-header__button md-logo" aria-label="The Bash Hackers Wiki" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> The Bash Hackers Wiki </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> The exec builtin command </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=m
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</code></pre></div> <h2 id=description>Description<a class=headerlink href=#description title="Permanent link">¶</a></h2> <p>The <code>exec</code> builtin command is used to</p> <ul> <li><strong>replace</strong> the shell with a given program (executing it, <strong>not as new process</strong>)</li> <li>set redirections for the program to execute or for the current shell</li> </ul> <p>If only redirections are given, the redirections affect the current shell without executing any program.</p> <h3 id=options>Options<a class=headerlink href=#options title="Permanent link">¶</a></h3> <table> <thead> <tr> <th>Option</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>-a NAME</code></td> <td>Passes <code>NAME</code> as zeroth argument for the program to be executed</td> </tr> <tr> <td><code>-c</code></td> <td>Execute the program with an empty (cleared) environment</td> </tr> <tr> <td><code>-l</code></td> <td>Prepends a dash (<code>-</code>) to the zeroth argument of the program to be executed, similar to what the <code>login</code> program does</td> </tr> </tbody> </table> <h3 id=exit-status>Exit status<a class=headerlink href=#exit-status title="Permanent link">¶</a></h3> <ul> <li>on redirection errors it returns 1, otherwise 0</li> <li>on exec failures:<ul> <li>a non-interactive shell terminates; if the <a href=../../../internals/shell_options/#execfail>shell option execfail</a> is set <code>exec</code> returns failure</li> <li>in an interactive shell, <code>exec</code> returns failure</li> </ul> </li> </ul> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <h3 id=wrapper-around-a-program>Wrapper around a program<a class=headerlink href=#wrapper-around-a-program title="Permanent link">¶</a></h3> <div class=highlight><pre><span></span><code><a id=__codelineno-0-1 name=__codelineno-0-1 href=#__codelineno-0-1></a><span class=nv>myprog</span><span class=o>=</span>/bin/ls
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<a id=__codelineno-0-2 name=__codelineno-0-2 href=#__codelineno-0-2></a><span class=nb>echo</span><span class=w> </span><span class=s2>"This is the wrapper script, it will exec </span><span class=nv>$myprog</span><span class=s2>"</span>
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<a id=__codelineno-0-3 name=__codelineno-0-3 href=#__codelineno-0-3></a>
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<a id=__codelineno-0-4 name=__codelineno-0-4 href=#__codelineno-0-4></a><span class=c1># do some vodoo here, probably change the arguments etc.</span>
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<a id=__codelineno-0-5 name=__codelineno-0-5 href=#__codelineno-0-5></a><span class=c1># well, stuff a wrapper is there for</span>
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<a id=__codelineno-0-6 name=__codelineno-0-6 href=#__codelineno-0-6></a>
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<a id=__codelineno-0-7 name=__codelineno-0-7 href=#__codelineno-0-7></a><span class=nb>exec</span><span class=w> </span><span class=s2>"</span><span class=nv>$myprog</span><span class=s2>"</span><span class=w> </span><span class=s2>"</span><span class=nv>$@</span><span class=s2>"</span>
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</code></pre></div> <h3 id=open-a-file-as-input-for-the-script>Open a file as input for the script<a class=headerlink href=#open-a-file-as-input-for-the-script title="Permanent link">¶</a></h3> <div class=highlight><pre><span></span><code><a id=__codelineno-1-1 name=__codelineno-1-1 href=#__codelineno-1-1></a><span class=c1># open it</span>
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<a id=__codelineno-1-2 name=__codelineno-1-2 href=#__codelineno-1-2></a><span class=nb>exec</span><span class=w> </span><span class=m>3</span><<span class=w> </span>input.txt
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<a id=__codelineno-1-3 name=__codelineno-1-3 href=#__codelineno-1-3></a>
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<a id=__codelineno-1-4 name=__codelineno-1-4 href=#__codelineno-1-4></a><span class=c1># for example: read one line from the file(-descriptor)</span>
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<a id=__codelineno-1-5 name=__codelineno-1-5 href=#__codelineno-1-5></a><span class=nb>read</span><span class=w> </span>-u<span class=w> </span><span class=m>3</span><span class=w> </span>LINE
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<a id=__codelineno-1-6 name=__codelineno-1-6 href=#__codelineno-1-6></a><span class=c1># or</span>
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<a id=__codelineno-1-7 name=__codelineno-1-7 href=#__codelineno-1-7></a><span class=nb>read</span><span class=w> </span>LINE<span class=w> </span><<span class=p>&</span><span class=m>3</span>
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<a id=__codelineno-1-8 name=__codelineno-1-8 href=#__codelineno-1-8></a>
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<a id=__codelineno-1-9 name=__codelineno-1-9 href=#__codelineno-1-9></a><span class=c1># finally, close it</span>
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<a id=__codelineno-1-10 name=__codelineno-1-10 href=#__codelineno-1-10></a><span class=nb>exec</span><span class=w> </span><span class=m>3</span><<span class=p>&</span>-
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</code></pre></div> <h3 id=overall-script-logfile>Overall script logfile<a class=headerlink href=#overall-script-logfile title="Permanent link">¶</a></h3> <p>To redirect the whole <code>stdout</code> and <code>stderr</code> of the shell or shellscript to a file, you can use the <code>exec</code> builtin command:</p> <div class=highlight><pre><span></span><code><a id=__codelineno-2-1 name=__codelineno-2-1 href=#__codelineno-2-1></a><span class=nb>exec</span><span class=w> </span>>/var/adm/my.log<span class=w> </span><span class=m>2</span>><span class=p>&</span><span class=m>1</span>
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<a id=__codelineno-2-2 name=__codelineno-2-2 href=#__codelineno-2-2></a>
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<a id=__codelineno-2-3 name=__codelineno-2-3 href=#__codelineno-2-3></a><span class=c1># script continues here...</span>
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</code></pre></div> <h2 id=portability-considerations>Portability considerations<a class=headerlink href=#portability-considerations title="Permanent link">¶</a></h2> <div class=highlight><pre><span></span><code>*POSIX(r) specifies error code ranges:
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* if ''exec'' can't find the program to execute, the error code shall be 126
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* on a redirection error, the error code shall be between 1 and 125
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* the ''-a NAME'' option appeared in Bash 4.2-alpha
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* POSIX(r) does **not** specify any options for ''exec'' (like ''-c'', ''-l'', ''-a NAME'').
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</code></pre></div> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../../../syntax/redirection/ >redirection</a></li> </ul> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date">November 13, 2024</span> </span> <span class=md-source-file__fact> <span class=md-icon title=Created> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M14.47 15.08 11 13V7h1.5v5.25l3.08 1.83c-.41.28-.79.62-1.11 1m-1.39 4.84c-.36.05-.71.08-1.08.08-4.42 0-8-3.58-8-8s3.58-8 8-8 8 3.58 8 8c0 .37-.03.72-.08 1.08.69.1 1.33.32 1.92.64.1-.56.16-1.13.16-1.72 0-5.5-4.5-10-10-10S2 6.5 2 12s4.47 10 10 10c.59 0 1.16-.06 1.72-.16-.32-.59-.54-1.23-.64-1.92M18 15v3h-3v2h3v3h2v-3h3v-2h-3v-3z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date">November 13, 2024</span> </span> </aside> <h2 id=__comments>Comments</h2> <script src=https://giscus.app/client.js data-repo=flokoe/bash-hackers-wiki data-repo-id=R_kgDOJ3Nr6Q data-category="Giscus Page Comments" data-category-id=DIC_kwDOJ3Nr6c4CXq9t data-mapping=pathname data-strict=1 data-reactions-enabled=1 data-emit-metadata=0 data-input-position=top data-theme=preferred_color_scheme data-lang=en data-loading=lazy crossorigin=anonymous async>
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