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<!--replace-end-7--><!--replace-end-4--><!--replace-end-1--></head><body><div class="ui fluid container universe"><!--replace-start-2--><!--replace-start-3--><!--replace-start-6--><div class="ui text container" id="zettel-container" style="position: relative"><div class="zettel-view"><article class="ui raised attached segment zettel-content"><div class="pandoc"><h1 id="title-h1">Loops in Bash</h1><h2 id="traditional-for-loop">Traditional for loop</h2><pre><code class="bash language-bash">for (( i=0; i<=5;i++ )); do
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echo $i
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done
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# 1 2 3 4 5</code></pre><h2 id="forin-loop-through-an-array"><code>for..in</code>: loop through an array</h2><pre><code class="bash language-bash">for element in "${arr[@]}"
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do
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echo "$element"
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done</code></pre><h2 id="while-loop">While loop</h2><blockquote><p><code>while</code> loops execute while a condition is true (0)</p></blockquote><p>We can use a <code>while</code> loop as a condition in two senses:</p><ul><li>execute while a given condition obtains</li><li>expand and execute a given command as long as the final command in the `while’ for the command has an exit status of zero (i.e. truthy)</li></ul><p>Here is an exampe of using <code>while</code> in the former case:</p><pre><code class="sh language-sh">declare -i n=0
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while (( n<10 ))
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do
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echo "n:$n"
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(( n++ ))
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done</code></pre><p>Here is an example of using <code>while</code> in the latter case:</p><pre><code class="sh language-sh">while read line;
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do
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# something
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done < "$file_to_read"</code></pre><h2 id="until-loop">Until loop</h2><blockquote><p><code>until</code> loops execute until a condition is false (1)</p></blockquote><pre><code class="sh language-sh">declare -i m=0
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until (( m==10 )): do
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echo "m:$m"
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(( m++ ))
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done</code></pre><p>This gives us the same output as <code>n</code> with the while loop but here it runs so long as <code>m==10</code> is false. As soon as <code>m</code> is equal to 100, the condition becomes true and hence the loop stops.</p></div></article><nav class="ui attached segment deemphasized bottomPane" id="neuron-tags-pane"><div><span class="ui basic label zettel-tag" title="Tag">shell</span></div></nav><nav class="ui bottom attached icon compact inverted menu blue" id="neuron-nav-bar"><!--replace-start-9--><!--replace-end-9--><a class="right item" href="impulse.html" title="Open Impulse"><i class="wave square icon"></i></a></nav></div></div><!--replace-end-6--><!--replace-end-3--><!--replace-end-2--><div class="ui center aligned container footer-version"><div class="ui tiny image"><a href="https://neuron.zettel.page"><img alt="logo" src="https://raw.githubusercontent.com/srid/neuron/master/assets/neuron.svg" title="Generated by Neuron 1.9.35.3" /></a></div></div></div></body></html> |