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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/syntax/pe/ rel=canonical><link href=../pattern/ rel=prev><link href=../quoting/ rel=next><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.5.44"><title>Parameter expansion - 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=#parameter-expansion 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> Parameter expansion </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=matchMedia("(prefers-color-scheme: li
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echo "The plural of $WORD is most likely ${WORD}s"
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</code></pre></div> <p><u>Why does the first one fail?</u> It prints nothing, because a parameter (variable) named "<code>WORDs</code>" is undefined and thus printed as "" (<em>nothing</em>). Without using braces for parameter expansion, Bash will interpret the sequence of all valid characters from the introducing "<code>$</code>" up to the last valid character as name of the parameter. When using braces you just force Bash to <strong>only interpret the name inside your braces</strong>.</p> <p>Also, please remember, that <strong>parameter names are</strong> (like nearly everything in UNIX®) <strong>case sensitive!</strong></p> <p>The second form with the curly braces is also needed to access positional parameters (arguments to a script) beyond <code>$9</code>:</p> <div class=highlight><pre><span></span><code>echo "Argument 1 is: $1"
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echo "Argument 10 is: ${10}"
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</code></pre></div> <h3 id=simple-usage-arrays>Simple usage: Arrays<a class=headerlink href=#simple-usage-arrays title="Permanent link">¶</a></h3> <p>See also the <a href=../arrays/ >article about general array syntax</a></p> <p>For arrays you always need the braces. The arrays are expanded by individual indexes or mass arguments. An individual index behaves like a normal parameter, for the mass expansion, please read the article about arrays linked above.</p> <ul> <li><code>${array[5]}</code></li> <li><code>${array[*]}</code></li> <li><code>${array[@]}</code></li> </ul> <h2 id=indirection>Indirection<a class=headerlink href=#indirection title="Permanent link">¶</a></h2> <p><code>${!PARAMETER}</code></p> <p>In some cases, like for example</p> <div class=highlight><pre><span></span><code>${PARAMETER}
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${PARAMETER:0:3}
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</code></pre></div> <p>you can instead use the form</p> <div class=highlight><pre><span></span><code>${!PARAMETER}
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</code></pre></div> <p>to enter a level of indirection. The referenced parameter is not <code>PARAMETER</code> itself, but the parameter whose name is stored as the value of <code>PARAMETER</code>. If the parameter <code>PARAMETER</code> has the value "<code>TEMP</code>", then <code>${!PARAMETER}</code> will expand to the value of the parameter named <code>TEMP</code>:</p> <div class=highlight><pre><span></span><code>read -rep 'Which variable do you want to inspect? ' look_var
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printf 'The value of "%s" is: "%s"\n' "$look_var" "${!look_var}"
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</code></pre></div> <p>Of course the indirection also works with special variables:</p> <div class=highlight><pre><span></span><code># set some fake positional parameters
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set one two three four
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# get the LAST argument ("#" stores the number of arguments, so "!#" will reference the LAST argument)
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echo ${!#}
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</code></pre></div> <p>You can think of this mechanism as being roughly equivalent to taking any parameter expansion that begins with the parameter name, and substituting the <code>!PARAMETER</code> part with the value of PARAMETER.</p> <div class=highlight><pre><span></span><code>echo "${!var^^}"
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# ...is equivalent to
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eval 'echo "${'"$var"'^^}"'
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</code></pre></div> <p>It was an unfortunate design decision to use the <code>!</code> prefix for indirection, as it introduces parsing ambiguity with other parameter expansions that begin with <code>!</code>. Indirection is not possible in combination with any parameter expansion whose modifier requires a prefix to the parameter name. Specifically, indirection isn't possible on the <code>${!var@}</code>, <code>${!var*}</code>, <code>${!var[@]}</code>, <code>${!var[*]}</code>, and <code>${#var}</code> forms. This means the <code>!</code> prefix can't be used to retrieve the indices of an array, the length of a string, or number of elements in an array indirectly (see <a href=../arrays/#indirection>syntax/arrays#indirection</a> for workarounds). Additionally, the <code>!</code>-prefixed parameter expansion conflicts with ksh-like shells which have the more powerful "name-reference" form of indirection, where the exact same syntax is used to expand to the name of the variable being referenced.</p> <p>Indirect references to <a href=../arrays/ >array names</a> are also possible since the Bash 3 series (exact version unknown), but undocumented. See <a href=../arrays/#indirection>syntax/arrays#indirection</a> for details.</p> <p>Chet has added an initial implementation of the ksh <code>nameref</code> declaration command to the git devel branch. (<code>declare -n</code>, <code>local -n</code>, etc, will be supported). This will finally address many issues around passing and returning complex datatypes to/from functions.</p> <h2 id=case-modification>Case modification<a class=headerlink href=#case-modification title="Permanent link">¶</a></h2> <p><code>${PARAMETER^}</code></p> <p><code>${PARAMETER^^}</code></p> <p><code>${PARAMETER,}</code></p> <p><code>${PARAMETER,,}</code></p> <p><code>${PARAMETER~}</code></p> <p><code>${PARAMETER~~}</code></p> <p>These expansion operators modify the case of the letters in the expanded text.</p> <p>The <code>^</code> operator modifies the first character to uppercase, the <code>,</code> operator to lowercase. When using the double-form (<code>^^</code> and <code>,,</code>), all characters are converted.</p> <p><wrap center round info 60%></p> <p>The (<strong>currently undocumented</strong>) operators <code>~</code> and <code>~~</code> reverse the case of the given text (in <code>PARAMETER</code>).<code>~</code> reverses the case of first letter of words in the variable while <code>~~</code> reverses case for all. Thanks to <code>Bushmills</code> and <code>geirha</code> on the Freenode IRC channel for this finding.</p> <p></wrap></p> <p><u><strong>Example: Rename all <code>*.txt</code> filenames to lowercase</strong></u></p> <div class=highlight><pre><span></span><code>for file in *.txt; do
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mv "$file" "${file,,}"
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done
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</code></pre></div> <p><u><strong>Note:</strong></u> Case modification is a handy feature you can apply to a name or a title. Or is it? Case modification was an important aspect of the Bash 4 release. Bash version 4, RC1 would perform word splitting, and then case modification, resulting in title case (where every word is capitalized). It was decided to apply case modification to values, not words, for the Bash 4 release. Thanks Chet.</p> <h3 id=case-modification-arrays>Case modification: Arrays<a class=headerlink href=#case-modification-arrays title="Permanent link">¶</a></h3> <p>Case modification can be used to create the proper capitalization for names or titles. Just assign it to an array:</p> <p><code>declare -a title=(my hello world john smith)</code></p> <p>For <a href=../arrays/ >array</a> expansion, the case modification applies to <strong>every expanded element, no matter if you expand an individual index or mass-expand</strong> the whole array using <code>@</code> or <code>*</code> subscripts. Some examples:</p> <p>Assume: <code>array=(This is some Text)</code></p> <ul> <li><code>echo "${array[@],}"</code><ul> <li>=> <code>this is some text</code></li> </ul> </li> <li><code>echo "${array[@],,}"</code><ul> <li>=> <code>this is some text</code></li> </ul> </li> <li><code>echo "${array[@]^}"</code><ul> <li>=> <code>This Is Some Text</code></li> </ul> </li> <li> <p><code>echo "${array[@]^^}"</code></p> <ul> <li> <p>=> <code>THIS IS SOME TEXT</code></p> </li> <li> <p>''echo "${array[2]^^}"''</p> </li> <li>=> ''SOME''</li> </ul> </li> </ul> <h2 id=variable-name-expansion>Variable name expansion<a class=headerlink href=#variable-name-expansion title="Permanent link">¶</a></h2> <p><code>${!PREFIX*}</code></p> <p><code>${!PREFIX@}</code></p> <p>This expands to a list of all set <strong>variable names</strong> beginning with the string <code>PREFIX</code>. The elements of the list are separated by the first character in the <code>IFS</code>-variable (<space> by default).</p> <p>This will show all defined variable names (not values!) beginning with "BASH":</p> <div class=highlight><pre><span></span><code>$ echo ${!BASH*}
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BASH BASH_ARGC BASH_ARGV BASH_COMMAND BASH_LINENO BASH_SOURCE BASH_SUBSHELL BASH_VERSINFO BASH_VERSION
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</code></pre></div> <p>This list will also include <a href=../arrays/ >array names</a>.</p> <h2 id=substring-removal>Substring removal<a class=headerlink href=#substring-removal title="Permanent link">¶</a></h2> <p><code>${PARAMETER#PATTERN}</code></p> <p><code>${PARAMETER##PATTERN}</code></p> <p><code>${PARAMETER%PATTERN}</code></p> <p><code>${PARAMETER%%PATTERN}</code></p> <p>This one can <strong>expand only a part</strong> of a parameter's value, <strong>given a pattern to describe what to remove</strong> from the string. The pattern is interpreted just like a pattern to describe a filename to match (globbing). See <a href=../pattern/ >Pattern matching</a> for more.</p> <p>Example string (<em>just a quote from a big man</em>):</p> <div class=highlight><pre><span></span><code>MYSTRING="Be liberal in what you accept, and conservative in what you send"
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</code></pre></div> <h3 id=from-the-beginning>From the beginning<a class=headerlink href=#from-the-beginning title="Permanent link">¶</a></h3> <p><code>${PARAMETER#PATTERN}</code> and <code>${PARAMETER##PATTERN}</code></p> <p>This form is to remove the described <a href=../pattern/ >pattern</a> trying to <strong>match it from the beginning of the string</strong>. The operator "<code>#</code>" will try to remove the shortest text matching the pattern, while "<code>##</code>" tries to do it with the longest text matching. Look at the following examples to get the idea (matched text ~~marked striked~~, remember it will be removed!):</p> <p>Syntax Result</p> <hr> <p><code>${MYSTRING#*in}</code> ~~Be liberal in~~ what you accept, and conservative in what you send <code>${MYSTRING##*in}</code> ~~Be liberal in what you accept, and conservative in~~ what you send</p> <h3 id=from-the-end>From the end<a class=headerlink href=#from-the-end title="Permanent link">¶</a></h3> <p><code>${PARAMETER%PATTERN}</code> and <code>${PARAMETER%%PATTERN}</code></p> <p>In the second form everything will be the same, except that Bash now tries to match the pattern from the end of the string:</p> <p>Syntax Result</p> <hr> <p><code>${MYSTRING%in*}</code> Be liberal in what you accept, and conservative ~~in what you send~~ <code>${MYSTRING%%in*}</code> Be liberal ~~in what you accept, and conservative in what you send~~</p> <p>The second form nullifies variables that begin with <code>in</code>, by working from the end.</p> <h3 id=common-use>Common use<a class=headerlink href=#common-use title="Permanent link">¶</a></h3> <p><u><strong>How the heck does that help to make my life easier?</strong></u></p> <p>Well, maybe the most common use for it is to <strong>extract parts of a filename</strong>. Just look at the following list with examples:</p> <ul> <li><strong>Get name without extension</strong><ul> <li><code>${FILENAME%.*}</code></li> <li>=> <code>bash_hackers.txt</code></li> </ul> </li> <li><strong>Get extension</strong><ul> <li><code>${FILENAME##*.}</code></li> <li>=> <code>bash_hackers.txt</code></li> </ul> </li> <li><strong>Get directory name</strong><ul> <li><code>${PATHNAME%/*}</code></li> <li>=> <code>/home/bash/bash_hackers.txt</code></li> </ul> </li> <li><strong>Get filename</strong><ul> <li><code>${PATHNAME##*/}</code></li> <li>=> <code>/home/bash/bash_hackers.txt</code></li> </ul> </li> </ul> <p>These are the syntaxes for filenames with a single extension. Depending on your needs, you might need to adjust shortest/longest match.</p> <h3 id=substring-removal-arrays>Substring removal: Arrays<a class=headerlink href=#substring-removal-arrays title="Permanent link">¶</a></h3> <p>As for most parameter expansion features, working on <a href=../arrays/ >arrays</a> <strong>will handle each expanded element</strong>, for individual expansion and also for mass expansion.</p> <p>Simple example, removing a trailing <code>is</code> from all array elements (on expansion):</p> <p>Assume: <code>array=(This is a text)</code></p> <ul> <li><code>echo "${array[@]%is}"</code><ul> <li>=> <code>Th a text</code></li> <li>(it was: <code>This is a text</code>)</li> </ul> </li> </ul> <p>All other variants of this expansion behave the same.</p> <h2 id=search-and-replace>Search and replace<a class=headerlink href=#search-and-replace title="Permanent link">¶</a></h2> <p><code>${PARAMETER/PATTERN/STRING}</code></p> <p><code>${PARAMETER//PATTERN/STRING}</code></p> <p><code>${PARAMETER/PATTERN}</code></p> <p><code>${PARAMETER//PATTERN}</code></p> <p>This one can substitute (<em>replace</em>) a substring <a href=../pattern/ >matched by a pattern</a>, on expansion time. The matched substring will be entirely removed and the given string will be inserted. Again some example string for the tests:</p> <div class=highlight><pre><span></span><code>MYSTRING="Be liberal in what you accept, and conservative in what you send"
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</code></pre></div> <p>The two main forms only differ in <strong>the number of slashes</strong> after the parameter name: <code>${PARAMETER/PATTERN/STRING}</code> and <code>${PARAMETER//PATTERN/STRING}</code></p> <p>The first one (<em>one slash</em>) is to only substitute <strong>the first occurrence</strong> of the given pattern, the second one (<em>two slashes</em>) is to substitute <strong>all occurrences</strong> of the pattern.</p> <p>First, let's try to say "happy" instead of "conservative" in our example string:</p> <div class=highlight><pre><span></span><code>${MYSTRING//conservative/happy}
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</code></pre></div> <p>=> <code>Be liberal in what you accept, and conservativehappy in what you send</code></p> <p>Since there is only one "conservative" in that example, it really doesn't matter which of the two forms we use.</p> <p>Let's play with the word "in", I don't know if it makes any sense, but let's substitute it with "by".</p> <p><u><strong>First form: Substitute first occurrence</strong></u></p> <div class=highlight><pre><span></span><code>${MYSTRING/in/by}
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</code></pre></div> <p>=> <code>Be liberal inby what you accept, and conservative in what you send</code></p> <p><u><strong>Second form: Substitute all occurrences</strong></u></p> <div class=highlight><pre><span></span><code>${MYSTRING//in/by}
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</code></pre></div> <p>=> <code>Be liberal inby what you accept, and conservative inby what you send</code></p> <p><u><strong>Anchoring</strong></u> Additionally you can "anchor" an expression: A <code>#</code> (hashmark) will indicate that your expression is matched against the beginning portion of the string, a <code>%</code> (percent-sign) will do it for the end portion.</p> <div class=highlight><pre><span></span><code>MYSTRING=xxxxxxxxxx
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echo ${MYSTRING/#x/y} # RESULT: yxxxxxxxxx
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echo ${MYSTRING/%x/y} # RESULT: xxxxxxxxxy
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</code></pre></div> <p>If the replacement part is completely omitted, the matches are replaced by the nullstring, i.e., they are removed. This is equivalent to specifying an empty replacement:</p> <div class=highlight><pre><span></span><code>echo ${MYSTRING//conservative/}
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# is equivalent to
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echo ${MYSTRING//conservative}
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</code></pre></div> <h3 id=search-and-replace-arrays>Search and replace: Arrays<a class=headerlink href=#search-and-replace-arrays title="Permanent link">¶</a></h3> <p>This parameter expansion type applied to <a href=../arrays/ >arrays</a> <strong>applies to all expanded elements</strong>, no matter if an individual element is expanded, or all elements using the mass expansion syntaxes.</p> <p>A simple example, changing the (lowercase) letter <code>t</code> to <code>d</code>:</p> <p>Assume: <code>array=(This is a text)</code></p> <ul> <li><code>echo "${array[@]/t/d}"</code><ul> <li>=> <code>This is a dext</code></li> </ul> </li> <li><code>echo "${array[@]//t/d}"</code><ul> <li>=> <code>This is a dexd</code></li> </ul> </li> </ul> <h2 id=string-length>String length<a class=headerlink href=#string-length title="Permanent link">¶</a></h2> <p><code>${#PARAMETER}</code></p> <p>When you use this form, the length of the parameter's value is expanded. Again, a quote from a big man, to have a test text:</p> <div class=highlight><pre><span></span><code>MYSTRING="Be liberal in what you accept, and conservative in what you send"
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</code></pre></div> <p>Using echo <code>${#MYSTRING}</code>...</p> <p>=> <code>64</code></p> <p>The length is reported in characters, not in bytes. Depending on your environment this may not always be the same (multibyte-characters, like in UTF8 encoding).</p> <p>There's not much to say about it, mh?</p> <h3 id=string-length-arrays>(String) length: Arrays<a class=headerlink href=#string-length-arrays title="Permanent link">¶</a></h3> <p>For <a href=../arrays/ >arrays</a>, this expansion type has two meanings:</p> <ul> <li>For <strong>individual</strong> elements, it reports the string length of the element (as for every "normal" parameter)</li> <li>For the <strong>mass subscripts</strong> <code>@</code> and <code>*</code> it reports the number of set elements in the array</li> </ul> <p>Example:</p> <p>Assume: <code>array=(This is a text)</code></p> <ul> <li><code>echo ${#array[1]}</code><ul> <li>=> 2 (the word "is" has a length of 2)</li> </ul> </li> <li><code>echo ${#array[@]}</code><ul> <li>=> 4 (the array contains 4 elements)</li> </ul> </li> </ul> <p><u><strong>Attention:</strong></u> The number of used elements does not need to conform to the highest index. Sparse arrays are possible in Bash, that means you can have 4 elements, but with indexes 1, 7, 20, 31. <strong>You can't loop through such an array with a counter loop based on the number of elements!</strong></p> <h2 id=substring-expansion>Substring expansion<a class=headerlink href=#substring-expansion title="Permanent link">¶</a></h2> <p><code>${PARAMETER:OFFSET}</code></p> <p><code>${PARAMETER:OFFSET:LENGTH}</code></p> <p>This one can expand only a <strong>part</strong> of a parameter's value, given a <strong>position to start</strong> and maybe a <strong>length</strong>. If <code>LENGTH</code> is omitted, the parameter will be expanded up to the end of the string. If <code>LENGTH</code> is negative, it's taken as a second offset into the string, counting from the end of the string.</p> <p><code>OFFSET</code> and <code>LENGTH</code> can be <strong>any</strong> <a href=../arith_expr/ >arithmetic expression</a>. <strong>Take care:</strong> The <code>OFFSET</code> starts at 0, not at 1!</p> <p>Example string (a quote from a big man): <code>MYSTRING="Be liberal in what you accept, and conservative in what you send"</code></p> <h3 id=using-only-offset>Using only Offset<a class=headerlink href=#using-only-offset title="Permanent link">¶</a></h3> <p>In the first form, the expansion is used without a length value, note that the offset 0 is the first character:</p> <div class=highlight><pre><span></span><code>echo ${MYSTRING:35}
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</code></pre></div> <p>=> <code><del>Be liberal in what you accept, and </del>conservative in what you send</code></p> <h3 id=using-offset-and-length>Using Offset and Length<a class=headerlink href=#using-offset-and-length title="Permanent link">¶</a></h3> <p>In the second form we also give a length value:</p> <div class=highlight><pre><span></span><code>echo ${MYSTRING:35:12}
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</code></pre></div> <p>=> <code><del>Be liberal in what you accept, and </del>conservative<del> in what you send</del></code></p> <h3 id=negative-offset-value>Negative Offset Value<a class=headerlink href=#negative-offset-value title="Permanent link">¶</a></h3> <p>If the given offset is negative, it's counted from the end of the string, i.e. an offset of -1 is the last character. In that case, the length still counts forward, of course. One special thing is to do when using a negative offset: You need to separate the (negative) number from the colon:</p> <div class=highlight><pre><span></span><code>${MYSTRING: -10:5}
|
||
|
|
${MYSTRING:(-10):5}
|
||
|
|
</code></pre></div> <p>Why? Because it's interpreted as the parameter expansion syntax to <a href=./#use_a_default_value>use a default value</a>.</p> <h3 id=negative-length-value>Negative Length Value<a class=headerlink href=#negative-length-value title="Permanent link">¶</a></h3> <p>If the <code>LENGTH</code> value is negative, it's used as offset from the end of the string. The expansion happens from the first to the second offset then:</p> <div class=highlight><pre><span></span><code>echo "${MYSTRING:11:-17}"
|
||
|
|
</code></pre></div> <p>=> <code><del>Be liberal </del>in what you accept, and conservative<del> in what you send</del></code></p> <p>This works since Bash 4.2-alpha, see also <a href=../../scripting/bashchanges/ >bashchanges</a>.</p> <h3 id=substringelement-expansion-arrays>Substring/Element expansion: Arrays<a class=headerlink href=#substringelement-expansion-arrays title="Permanent link">¶</a></h3> <p>For <a href=../arrays/ >arrays</a>, this expansion type has again 2 meanings:</p> <ul> <li>For <strong>individual</strong> elements, it expands to the specified substring (as for every "normal" parameter)</li> <li>For the <strong>mass subscripts</strong> <code>@</code> and <code>*</code> it mass-expands individual array elements denoted by the 2 numbers given (<em>starting element</em>, <em>number of elements</em>)</li> </ul> <p>Example:</p> <p>Assume: <code>array=(This is a text)</code></p> <ul> <li><code>echo ${array[0]:2:2}</code><ul> <li>=> <code>is</code> (the "is" in "This", array element 0)</li> </ul> </li> <li><code>echo ${array[@]:1:2}</code><ul> <li>=> <code>is a</code> (from element 1 inclusive, 2 elements are expanded, i.e. element 1 and 2)</li> </ul> </li> </ul> <h2 id=use-a-default-value>Use a default value<a class=headerlink href=#use-a-default-value title="Permanent link">¶</a></h2> <p><code>${PARAMETER:-WORD}</code></p> <p><code>${PARAMETER-WORD}</code></p> <p>If the parameter <code>PARAMETER</code> is unset (never was defined) or null (empty), this one expands to <code>WORD</code>, otherwise it expands to the value of <code>PARAMETER</code>, as if it just was <code>${PARAMETER}</code>. If you omit the <code>:</code> (colon), like shown in the second form, the default value is only used when the parameter was <strong>unset</strong>, not when it was empty.</p> <div class=highlight><pre><span></span><code>echo "Your home directory is: ${HOME:-/home/$USER}."
|
||
|
|
echo "${HOME:-/home/$USER} will be used to store your personal data."
|
||
|
|
</code></pre></div> <p>If <code>HOME</code> is unset or empty, everytime you want to print something useful, you need to put that parameter syntax in.</p> <div class=highlight><pre><span></span><code>#!/bin/bash
|
||
|
|
|
||
|
|
read -p "Enter your gender (just press ENTER to not tell us): " GENDER
|
||
|
|
echo "Your gender is ${GENDER:-a secret}."
|
||
|
|
</code></pre></div> <p>It will print "Your gender is a secret." when you don't enter the gender. Note that the default value is <strong>used on expansion time</strong>, it is <strong>not assigned to the parameter</strong>.</p> <h3 id=use-a-default-value-arrays>Use a default value: Arrays<a class=headerlink href=#use-a-default-value-arrays title="Permanent link">¶</a></h3> <p>For <a href=../arrays/ >arrays</a>, the behaviour is very similar. Again, you have to make a difference between expanding an individual element by a given index and mass-expanding the array using the <code>@</code> and <code>*</code> subscripts.</p> <ul> <li>For individual elements, it's the very same: If the expanded element is <code>NULL</code> or unset (watch the <code>:-</code> and <code>-</code> variants), the default text is expanded</li> <li>For mass-expansion syntax, the default text is expanded if the array<ul> <li>contains no element or is unset (the <code>:-</code> and <code>-</code> variants mean the <strong>same</strong> here)</li> <li>contains only elements that are the nullstring (the <code>:-</code> variant)</li> </ul> </li> </ul> <p>In other words: The basic meaning of this expansion type is applied as consistent as possible to arrays.</p> <p>Example code (please try the example cases yourself):</p> <div class=highlight><pre><span></span><code>####
|
||
|
|
# Example cases for unset/empty arrays and nullstring elements
|
||
|
|
####
|
||
|
|
|
||
|
|
|
||
|
|
### CASE 1: Unset array (no array)
|
||
|
|
|
||
|
|
# make sure we have no array at all
|
||
|
|
unset array
|
||
|
|
|
||
|
|
echo ${array[@]:-This array is NULL or unset}
|
||
|
|
echo ${array[@]-This array is NULL or unset}
|
||
|
|
|
||
|
|
### CASE 2: Set but empty array (no elements)
|
||
|
|
|
||
|
|
# declare an empty array
|
||
|
|
array=()
|
||
|
|
|
||
|
|
echo ${array[@]:-This array is NULL or unset}
|
||
|
|
echo ${array[@]-This array is NULL or unset}
|
||
|
|
|
||
|
|
|
||
|
|
### CASE 3: An array with only one element, a nullstring
|
||
|
|
array=("")
|
||
|
|
|
||
|
|
echo ${array[@]:-This array is NULL or unset}
|
||
|
|
echo ${array[@]-This array is NULL or unset}
|
||
|
|
|
||
|
|
|
||
|
|
### CASE 4: An array with only two elements, a nullstring and a normal word
|
||
|
|
array=("" word)
|
||
|
|
|
||
|
|
echo ${array[@]:-This array is NULL or unset}
|
||
|
|
echo ${array[@]-This array is NULL or unset}
|
||
|
|
</code></pre></div> <h2 id=assign-a-default-value>Assign a default value<a class=headerlink href=#assign-a-default-value title="Permanent link">¶</a></h2> <p><code>${PARAMETER:=WORD}</code></p> <p><code>${PARAMETER=WORD}</code></p> <p>This one works like the <a href=./#use_a_default_value>using default values</a>, but the default text you give is not only expanded, but also <strong>assigned</strong> to the parameter, if it was unset or null. Equivalent to using a default value, when you omit the <code>:</code> (colon), as shown in the second form, the default value will only be assigned when the parameter was <strong>unset</strong>.</p> <div class=highlight><pre><span></span><code>echo "Your home directory is: ${HOME:=/home/$USER}."
|
||
|
|
echo "$HOME will be used to store your personal data."
|
||
|
|
</code></pre></div> <p>After the first expansion here (<code>${HOME:=/home/$USER}</code>), <code>HOME</code> is set and usable.</p> <p>Let's change our code example from above:</p> <div class=highlight><pre><span></span><code>#!/bin/bash
|
||
|
|
|
||
|
|
read -p "Enter your gender (just press ENTER to not tell us): " GENDER
|
||
|
|
echo "Your gender is ${GENDER:=a secret}."
|
||
|
|
echo "Ah, in case you forgot, your gender is really: $GENDER"
|
||
|
|
</code></pre></div> <h3 id=assign-a-default-value-arrays>Assign a default value: Arrays<a class=headerlink href=#assign-a-default-value-arrays title="Permanent link">¶</a></h3> <p>For <a href=../arrays/ >arrays</a> this expansion type is limited. For an individual index, it behaves like for a "normal" parameter, the default value is assigned to this one element. The mass-expansion subscripts <code>@</code> and <code>*</code> <strong>can not be used here</strong> because it's not possible to assign to them!</p> <h2 id=use-an-alternate-value>Use an alternate value<a class=headerlink href=#use-an-alternate-value title="Permanent link">¶</a></h2> <p><code>${PARAMETER:+WORD}</code></p> <p><code>${PARAMETER+WORD}</code></p> <p>This form expands to nothing if the parameter is unset or empty. If it is set, it does not expand to the parameter's value, <strong>but to some text you can specify</strong>:</p> <div class=highlight><pre><span></span><code>echo "The Java application was installed and can be started.${JAVAPATH:+ NOTE: JAVAPATH seems to be set}"
|
||
|
|
</code></pre></div> <p>The above code will simply add a warning if <code>JAVAPATH</code> is set (because it could influence the startup behaviour of that imaginary application).</p> <p>Some more unrealistic example... Ask for some flags (for whatever reason), and then, if they were set, print a warning and also print the flags:</p> <div class=highlight><pre><span></span><code>#!/bin/bash
|
||
|
|
|
||
|
|
read -p "If you want to use special flags, enter them now: " SPECIAL_FLAGS
|
||
|
|
echo "The installation of the application is finished${SPECIAL_FLAGS:+ (NOTE: there are special flags set: $SPECIAL_FLAGS)}."
|
||
|
|
</code></pre></div> <p>If you omit the colon, as shown in the second form (<code>${PARAMETER+WORD}</code>), the alternate value will be used if the parameter is set (and it can be empty)! You can use it, for example, to complain if variables you need (and that can be empty) are undefined:</p> <div class=highlight><pre><span></span><code># test that with the three stages:
|
||
|
|
|
||
|
|
# unset foo
|
||
|
|
# foo=""
|
||
|
|
# foo="something"
|
||
|
|
|
||
|
|
if [[ ${foo+isset} = isset ]]; then
|
||
|
|
echo "foo is set..."
|
||
|
|
else
|
||
|
|
echo "foo is not set..."
|
||
|
|
fi
|
||
|
|
</code></pre></div> <h3 id=use-an-alternate-value-arrays>Use an alternate value: Arrays<a class=headerlink href=#use-an-alternate-value-arrays title="Permanent link">¶</a></h3> <p>Similar to the cases for <a href=../arrays/ >arrays</a> to expand to a default value, this expansion behaves like for a "normal" parameter when using individual array elements by index, but reacts differently when using the mass-expansion subscripts <code>@</code> and <code>*</code>:</p> <div class=highlight><pre><span></span><code> * For individual elements, it's the very same: If the expanded element is **not** NULL or unset (watch the :+ and + variants), the alternate text is expanded
|
||
|
|
* For mass-expansion syntax, the alternate text is expanded if the array
|
||
|
|
* contains elements where min. one element is **not** a nullstring (the :+ and + variants mean the same here)
|
||
|
|
* contains **only** elements that are **not** the nullstring (the :+ variant)
|
||
|
|
</code></pre></div> <p>For some cases to play with, please see the code examples in the <a href=#use_a_default_valuearrays>description for using a default value</a>.</p> <h2 id=display-error-if-null-or-unset>Display error if null or unset<a class=headerlink href=#display-error-if-null-or-unset title="Permanent link">¶</a></h2> <p><code>${PARAMETER:?WORD}</code></p> <p><code>${PARAMETER?WORD}</code></p> <p>If the parameter <code>PARAMETER</code> is set/non-null, this form will simply expand it. Otherwise, the expansion of <code>WORD</code> will be used as appendix for an error message:</p> <div class=highlight><pre><span></span><code>$ echo "The unset parameter is: ${p_unset?not set}"
|
||
|
|
bash: p_unset: not set
|
||
|
|
</code></pre></div> <p>After printing this message,</p> <ul> <li>an interactive shell has <code>$?</code> to a non-zero value</li> <li>a non-interactive shell exits with a non-zero exit code</li> </ul> <p>The meaning of the colon (<code>:</code>) is the same as for the other parameter expansion syntaxes: It specifies if</p> <ul> <li>only unset or</li> <li>unset and empty parameters</li> </ul> <p>are taken into account.</p> <h2 id=code-examples>Code examples<a class=headerlink href=#code-examples title="Permanent link">¶</a></h2> <h3 id=substring-removal_1>Substring removal<a class=headerlink href=#substring-removal_1 title="Permanent link">¶</a></h3> <p>Removing the first 6 characters from a text string:</p> <div class=highlight><pre><span></span><code>STRING="Hello world"
|
||
|
|
|
||
|
|
# only print 'Hello'
|
||
|
|
echo "${STRING%??????}"
|
||
|
|
|
||
|
|
# only print 'world'
|
||
|
|
echo "${STRING#??????}"
|
||
|
|
|
||
|
|
# store it into the same variable
|
||
|
|
STRING=${STRING#??????}
|
||
|
|
</code></pre></div> <h2 id=bugs-and-portability-considerations>Bugs and Portability considerations<a class=headerlink href=#bugs-and-portability-considerations title="Permanent link">¶</a></h2> <ul> <li> <p><strong>Fixed in 4.2.36</strong> (<a href=ftp://ftp.cwru.edu/pub/bash/bash-4.2-patches/bash42-036>patch</a>). Bash doesn't follow either POSIX or its own documentation when expanding either a quoted <code>"$@"</code> or <code>"${arr[@]}"</code> with an adjacent expansion. <code>"$@$x"</code> expands in the same way as <code>"$*$x"</code> - i.e. all parameters plus the adjacent expansion are concatenated into a single argument. As a workaround, each expansion needs to be quoted separately. Unfortunately, this bug took a very long time to notice.<code>~ $ set -- a b c; x=foo; printf '<%s> ' "$@$x" "$*""$x" "$@""$x" <a b cfoo> <a b cfoo> <a> <b> <cfoo></code></p> </li> <li> <p>Almost all shells disagree about the treatment of an unquoted <code>$@</code>, <code>${arr[@]}</code>, <code>$*</code>, and <code>${arr[*]}</code> when <a href=http://mywiki.wooledge.org/IFS>IFS</a> is set to null. POSIX is unclear about the expected behavior. A null IFS causes both <a href=../expansion/wordsplit/ >word splitting</a> and <a href=../expansion/globs/ >pathname expansion</a> to behave randomly. Since there are few good reasons to leave <code>IFS</code> set to null for more than the duration of a command or two, and even fewer to expand <code>$@</code> and <code>$*</code> unquoted, this should be a rare issue. <strong>Always quote them</strong>!<code>touch x 'y z' for sh in bb {{d,b}a,{m,}k,z}sh; do echo "$sh" "$sh" -s a 'b c' d \* </dev/fd/0 done <<\EOF ${ZSH_VERSION+:} false && emulate sh IFS= printf '<%s> ' $* echo printf "<%s> " $@ echo EOF ``bb <ab cd*> <ab cd*> dash <ab cd*> <ab cd*> bash <a> <b c> <d> <x> <y z> <a> <b c> <d> <x> <y z> mksh <a b c d *> <a b c d *> ksh <a> <b c> <d> <x> <y z> <a> <b c> <d> <x> <y z> zsh <a> <b c> <d> <x> <y z> <a> <b c> <d> <x> <y z></code>When <code>IFS</code> is set to a non-null value, or unset, all shells behave the same - first expanding into separate args, then applying pathname expansion and word-splitting to the results, except for zsh, which doesn't do pathname expansion in its default mode.</p> </li> <li> <p>Additionally, shells disagree about various wordsplitting behaviors, the behavior of inserting delimiter characters from IFS in <code>$*</code>, and the way adjacent arguments are concatenated, when IFS is modified in the middle of expansion through side-effects.<code>for sh in bb {{d,b}a,po,{m,}k,z}sh; do printf '%-4s: ' "$sh" "$sh" </dev/fd/0 done <<\EOF ${ZSH_VERSION+:} false && emulate sh set -f -- a b c unset -v IFS printf '<%s> ' ${*}${IFS=}${*}${IFS:=-}"${*}" echo EOF ``bb : <a b cabc> <a-b-c> dash: <a b cabc> <a-b-c> bash: <a> <b> <ca> <b> <c-a b c> posh: <a> <b> <ca b c> <a-b-c> mksh: <a> <b> <ca b c> <a-b-c> ksh : <a> <b> <ca> <b> <c> <a b c> zsh : <a> <b> <ca> <b> <c> <a-b-c></code>ksh93 and mksh can additionally achieve this side effect (and others) via the <code>${ cmds;}</code> expansion. I haven't yet tested every possible side-effect that can affect expansion halfway through expansion that way.</p> </li> <li> <p>As previously mentioned, the Bash form of indirection by prefixing a parameter expansion with a <code>!</code> conflicts with the same syntax used by mksh, zsh, and ksh93 for a different purpose. Bash will "slightly" modify this expansion in the next version with the addition of namerefs.</p> </li> <li> <p>Bash (and most other shells) don't allow .'s in identifiers. In ksh93, dots in v
|
||
|
|
$ typeset -a a=(meh bleh blerg) b
|
||
|
|
$ IFS=e
|
||
|
|
$ printf "<%s> " ${b[@]-"${a[@]}" "${a[@]}"}; echo # Inner quotes make inner expansions quoted.
|
||
|
|
<meh> <bleh> <blerg meh> <bleh> <blerg>
|
||
|
|
$ printf "<%s> " ${b[@]-${a[@]} ${a[@]}}; echo' # No quotes at all wordsplits / globs, like you'd expect.
|
||
|
|
<m> <h> <bl> <h> <bl> <rg m> <h> <bl> <h> <bl> <rg>
|
||
|
|
</code></pre></div> <p>This all might be intuitive, and is the most common implementation, but this design sucks for a number of reasons. For one, it means Bash makes it absolutely impossible to expand any part of the inner region <em>unquoted</em> while leaving the outer region quoted. Quoting the outer forces quoting of the inner regions recursively (except nested command substitutions of course). Word-splitting is necessary to split words of the inner region, which cannot be done together with outer quoting. Consider the following (only slightly far-fetched) code:</p> <div class=highlight><pre><span></span><code># Bash (non-working example)
|
||
|
|
|
||
|
|
unset -v IFS # make sure we have a default IFS
|
||
|
|
|
||
|
|
if some crap; then
|
||
|
|
typeset -a someCmd=(myCmd arg1 'arg2 yay!' 'third*arg*' 4)
|
||
|
|
fi
|
||
|
|
|
||
|
|
someOtherCmd=mycommand
|
||
|
|
typeset -a otherArgs=(arg3 arg4)
|
||
|
|
|
||
|
|
# What do you think the programmer expected to happen here?
|
||
|
|
# What do you think will actually happen...
|
||
|
|
|
||
|
|
"${someCmd[@]-"$someOtherCmd" arg2 "${otherArgs[@]}"}" arg5
|
||
|
|
</code></pre></div> <p>This final line is perhaps not the most obvious, but I've run into cases were this type of logic can be desirable and realistic. We can deduce what was intended:</p> <ul> <li>If <code>someCmd</code> is set, then the resulting expansion should run the command: <code>"myCmd" "arg1" "arg2 yay!" "third*arg*" "4" "arg5"</code></li> <li>Otherwise, if <code>someCmd</code> is not set, expand <code>$someOtherCmd</code> and the inner args, to run a different command: <code>"mycommand" "arg2" "arg3" "arg4" "arg5"</code>.</li> </ul> <p>Unfortunately, it is impossible to get the intended result in Bash (and most other shells) without taking a considerably different approach. The only way to split the literal inner parts is through word-splitting, which requires that the PE be unquoted. But, the only way to expand the outer expansion correctly without word-splitting or globbing is to quote it. Bash will actually expand the command as one of these:</p> <div class=highlight><pre><span></span><code># The quoted PE produces a correct result here...
|
||
|
|
$ bash -c 'typeset -a someCmd=(myCmd arg1 "arg2 yay!" "third*arg*" 4); printf "<%s> " "${someCmd[@]-"$someOtherCmd" arg2 "${otherArgs[@]}"}" arg5; echo'
|
||
|
|
<myCmd> <arg1> <arg2 yay!> <third*arg*> <4> <arg5>
|
||
|
|
|
||
|
|
# ...but in the opposite case the first 3 arguments are glued together. There are no workarounds.
|
||
|
|
$ bash -c 'typeset -a otherArgs=(arg3 arg4); someOtherCmd=mycommand; printf "<%s> " "${someCmd[@]-"$someOtherCmd" arg2 "${otherArgs[@]}"}" arg5; echo'
|
||
|
|
<mycommand arg2 arg3> <arg4> <arg5>
|
||
|
|
|
||
|
|
# UNLESS! we unquote the outer expansion allowing the inner quotes to
|
||
|
|
# affect the necessary parts while allowing word-splitting to split the literals:
|
||
|
|
$ bash -c 'typeset -a otherArgs=(arg3 arg4); someOtherCmd=mycommand; printf "<%s> " ${someCmd[@]-"$someOtherCmd" arg2 "${otherArgs[@]}"} arg5; echo'
|
||
|
|
<mycommand> <arg2> <arg3> <arg4> <arg5>
|
||
|
|
|
||
|
|
# Success!!!
|
||
|
|
$ bash -c 'typeset -a someCmd=(myCmd arg1 "arg2 yay!" "third*arg*" 4); printf "<%s> " ${someCmd[@]-"$someOtherCmd" arg2 "${otherArgs[@]}"} arg5; echo'
|
||
|
|
<myCmd> <arg1> <arg2> <yay!> <third*arg*> <4> <arg5>
|
||
|
|
|
||
|
|
# ...Ah f^^k. (again, no workaround possible.)
|
||
|
|
</code></pre></div> <h4 id=the-ksh93-exception>The ksh93 exception<a class=headerlink href=#the-ksh93-exception title="Permanent link">¶</a></h4> <p>To the best of my knowledge, ksh93 is the only shell that acts differently. Rather than forcing nested expansions into quoting, a quote at the beginning and end of the nested region will cause the quote state to reverse itself within the nested part. I have no idea whether it's an intentional or documented effect, but it does solve the problem and consequently adds a lot of potential power to these expansions.</p> <p>All we need to do is add two extra double-quotes:</p> <div class=highlight><pre><span></span><code># ksh93 passing the two failed tests from above:
|
||
|
|
|
||
|
|
$ ksh -c 'otherArgs=(arg3 arg4); someOtherCmd="mycommand"; printf "<%s> " "${someCmd[@]-""$someOtherCmd" arg2 "${otherArgs[@]}""}" arg5; echo'
|
||
|
|
<mycommand> <arg2> <arg3> <arg4> <arg5>
|
||
|
|
|
||
|
|
$ ksh -c 'typeset -a someCmd=(myCmd arg1 "arg2 yay!" "third*arg*" 4); printf "<%s> " "${someCmd[@]-""$someOtherCmd" arg2 "${otherArgs[@]}""}" arg5; echo'
|
||
|
|
<myCmd> <arg1> <arg2 yay!> <third*arg*> <4> <arg5>
|
||
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</code></pre></div> <p>This can be used to control the quote state of any part of any expansion to an arbitrary depth. Sadly, it is the only shell that does this and the difference may introduce a possible compatibility problem.</p> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li>Internal: <a href=../expansion/intro/ >Introduction to expansion and substitution</a></li> <li>Internal: <a href=../arrays/ >Arrays</a></li> <li>Dictionary, internal: <a href=../../dict/parameter/ >parameter</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 7, 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 7, 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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