Understand Awk Variables with 3 Practical Examples

<a id="aptureLink_gQhJKQ92Kn" style="padding: 0px 6px; float: left;" href="http://www.gnu.org/software/gawk/manual/gawk.html"><img style="border: 0px none;" title="The GNU Awk User's Guide" src="http://blog.amit-agarwal.com/wp-content/uploads/img.zemanta.com/ph/400x270_WebClip" alt="" width="400px" height="270px" />

<a id="aptureLink_CLV4LbC1Dr" style="padding: 0px 6px; float: right;" href="http://gnuwin32.sourceforge.net/packages/mawk.htm"><img style="border: 0px none;" title="Mawk for Windows" src="http://blog.amit-agarwal.com/wp-content/uploads/img.zemanta.com/ph/400x270_WebClip" alt="" width="400px" height="270px" /> This article is part of the on-going Awk Tutorial and Examples series. Like any other <a class="zem_slink freebase/en/programming_language" title="Programming language" rel="wikipedia" href="http://en.wikipedia.org/wiki/Programming_language">programming languages, Awk also has user defined variables and built-in variables. In this article let us review how to define and use <a class="zem_slink freebase/en/awk" title="AWK" rel="homepage" href="http://cm.bell-labs.com/cm/cs/awkbook/index.html">awk variables. Awk variables should begin with the letter, followed by it can consist of alpha numeric characters or underscore. Keywords […]

Quickly search and replace string with Regular expression in multiple files using perl

for i in *; do perl -p -w -e &#8217;s/a(.*)b.*/d$1e/g&#8217;  $i > temp/$i; done

for i in *; do perl -pi -w -e &#8217;s/a(.*)b.*/d$1e/g&#8217;  $i ; done

The first one can be used when you want to preserve the original file. The redirection will cause the file with replaced string to be written to the new location in the temp directory. Modify the same according to your needs.

The second can be used to modify the files in-line. Causing overwriting the original file.

grep -v with multiple patterns.

$ sed '/test/{/error|critical|warning/d}' somefile If you wanted to do all in one command, you could go w/ sed instead

• <a href="http://www.commandlinefu.com/commands/view/3882/grep-v-with-multiple-patterns.">View this command to comment, vote or add to favourites
• <a href="http://feeds2.feedburner.com/commands/by/pipping">View all commands by <a href="http://feeds2.feedburner.com/commands/by/pipping">pipping

<a href="http://www.commandlinefu.com"><img src="http://blog.amit-agarwal.co.in/wp-content/uploads/2010/08/header-logo.jpg" alt="" align="bottom" />

by David Winterbottom (<a href="http://codeinthehole.com">codeinthehole.com)

<a href="http://feedads.g.doubleclick.net/~a/J5B2Z5VTSlqhmd-2YMQ4ndmAu4U/0/da"><img src="http://blog.amit-agarwal.com/wp-content/uploads/img.zemanta.com/~a/J5B2Z5VTSlqhmd-2YMQ4ndmAu4U/0/di" alt="" align="bottom" />
<a href="http://feedads.g.doubleclick.net/~a/J5B2Z5VTSlqhmd-2YMQ4ndmAu4U/1/da"><img src="http://blog.amit-agarwal.com/wp-content/uploads/img.zemanta.com/~a/J5B2Z5VTSlqhmd-2YMQ4ndmAu4U/1/di" alt="" align="bottom" />

<img src="http://blog.amit-agarwal.com/wp-content/uploads/img.zemanta.com/~r/Command-line-fu/~4/LjKzo7FpzDU" alt="" width="1" height="1" align="bottom" />

URL: <a href="http://feedproxy.google.com/~r/Command-line-fu/~3/LjKzo7FpzDU/grep-v-with-multiple-patterns.">http://feedproxy.google.com/~r/Command-line-fu/~3/LjKzo7FpzDU/grep-v-with-multiple-patterns.<h6 class="zemanta-related-title" style="font-size: 1em;">Related articles by Zemanta <ul class="zemanta-article-ul"> <li class="zemanta-article-ul-li"><a href="http://www.seroundtable.com/archives/020935.html">Google&#8217;s &#8221;Show More Results&#8221; Plus Box (seroundtable.com) <li class="zemanta-article-ul-li"><a href="http://www.macworld.com/article/143351/2009/10/netprocesses.html?lsrc=rss_main">See which processes are using the Internet (macworld.com) <div class="zemanta-pixie" style="margin-top: 10px; height: 15px;"><a class="zemanta-pixie-a" title="Reblog this post [with Zemanta]" href="http://reblog.zemanta.com/zemified/cc60245b-7397-4d48-83b2-7bfb345ae7a9/"><img class="zemanta-pixie-img" style="border: medium none; float: right;" src="http://blog.amit-agarwal.co.in/wp-content/uploads/2010/08/reblog_e20.png" alt="Reblog this post [with Zemanta]" /><span class="zem-script more-related pretty-attribution">