41 lines
1.2 KiB
HTML
41 lines
1.2 KiB
HTML
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---
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layout: page
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category-page: intermediate
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category-title: Intermediate commands
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tags: watch repeat track analyse seconds
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author: Claudio Maggioni
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title: watch
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---
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<p>
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The <code>watch</code> command is a system utility able to execute a command
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every <em>n</em> seconds by clearing the screen and displaying the
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output of the command each time the interval is over. This command is very
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simple to use and very effective: it can be used to check the size in bytes
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of a file while downloading it, or it can be used on <em>Linux</em> to jiggle
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around the mouse every ~5 minutes with the command <code>xdotool</code> in
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order to keep the computer awake.
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</p>
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<h3>Usage</h3>
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<p>
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<code>watch</code> has a very simple syntax: the amount in seconds to wait
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between executions is specified in seconds using the <code>-n</code> flag
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and the default value is <em>2</em>. Also, differences between older and
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newer outputs are highlighted if the <code>-d</code> flag is used.
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</p>
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<h4>Watch the size of "ubuntu.iso" every 5 seconds</h4>
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<pre>
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watch -n 5 du -h ubuntu.iso
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</pre>
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<h4>Watch the contents of "site.html" every 2 seconds and highlight the
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differencies between iterations</h4>
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<pre>
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watch -d cat site.html
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</pre>
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