07c79772dd
git-svn-id: svn+ssh://atelier.inf.usi.ch/home/bevilj/group-1@247 a672b425-5310-4d7a-af5c-997e18724b81
51 lines
1.8 KiB
HTML
51 lines
1.8 KiB
HTML
---
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layout: page
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author: Agostino Monti
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category-page: advanced
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category-title: Advanced commands
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tags: head tail text file
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title: head-tail
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---
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<br>
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<br>
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<h3><code>head</code></h3>
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<p>The <code>head</code> command reads the first few lines of any text given to it as an input
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and writes them to standard output.
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If more than one input file is provided, head will return the first ten lines
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from each file, precede each set of lines by the name of the file and separate
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each set of lines by one vertical space. </p>
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<br>
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<h3><code>tail</code></h3>
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<p>The tail command is similar to the head command
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except that it reads the final lines in files rather than the first lines.</p>
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<h4>Examples</h4>
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<p><pre>
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head file1.txt <br>
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head file1.txt file2.txt <br>
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tail fail1.txt</pre></p>
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<h3>flags</h3>
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<ul>
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<li>The <code>-n</code> option can be used followed by an integer indicating the number of lines desired.
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-n is a very tolerant option, it is not necessary for the integer to directly
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follow it without a space in between. In fact, the letter <i>n</i> does not
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even need to be used at all. Just the hyphen and the integer
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(with no intervening space) are sufficient to tell head how many lines to return.
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<h4>Examples</h4>
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<pre>
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head -n15 file1.txt <br>
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head -n 15 file1.txt <br>
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head -15 file1.txt</pre></li>
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<li>The output from other commands can be sent via a pipe (represented by the vertical bar character)
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to head to use as its input. The following sends the output from the ls command
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to head, which, in turn, displays the first ten lines of the output that it receives from ls
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<h4>Examples</h4>
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<pre>
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ls | head </pre></li>
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</ul>
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