Ranking of the most frequently used commands

Lets take a quick look at how to get the most frequently used commands on you shell. So what we need to do is this:

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      history | awk '{print $2}' | awk 'BEGIN {FS="|"}{print $1}' | sort | uniq -c | sort -n | tail | sort -nr
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So, how did we arrive at this and will this always work? No it might not always work. A typical example is where HISTTIMEFORMAT variable is set. In that case, if you check history, you will see that after the number column we have time and date in the specified format, in which case, you will get wrong information from the above command. Anyways, forgetting these special cases, lets go to how we got this command:

bash math

some quick links :

http://mainstreetanswers.org/bash/math.php
http://www.faqs.org/docs/abs/HTML/mathc.html
http://tldp.org/LDP/abs/html/mathc.html

Related articles

• W3C Announces MathML 3, New Standards for Math on the Web (readwriteweb.com)
• Find all the missing paths in the PATH variable in bash script (amit-agarwal.co.in)
• Nice site for Math related games and resources… (greenbananablog.org)
• bash 4.0 – new feature mapfile (amit-agarwal.co.in)

fork a new process in perl

I was doing something today and found that I require to fork a new process in perl. Now I had never done this earlier, so I did not know how to do this.

First some background :

I was doing some program very similar to http server, where the script accepts some input through a socket and then processes the same. In doing so I was seeing that the script was taking some time in processing the input and thus was not processing the second request until the first one was completed. Simple solution, fork the process.

bash mathematical calculators.

To start with , the most simple and easy to use should be “bc”. but just for some guys who want to be more experimental, here are few more bash calulator programs. These are completely command line and thus you can completely integrate them in your shell script or use them in shell script to do some really crazy maths calculations.

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      sudo yum install calc clac
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Lets start with installing these. Before we start, don’t blame and flame me if your favourite is not there in the list. If it is not, better is you drop me  a comment or email, and I will see, if I can include it in the list above, but remember this is only for console based calculators.

shopt causes bash completion to stop working.

Couple of days, I added some scripts to my bash startup and suddenly realized that bash completions stopped working. This is tricky situation in bash to figure out what went wrong. So, I set my foot down to make sure that I find out the culprit. Thus I started with method of elimination. So, I started with nothing in .bashrc and kept adding my stuff in batches, until the said feature was broken. Once that happened I started removing the added ones, one by one, until my completion started working again.

First earning on the blog in the form of advertising

Thanks to all my visitors, I was approached by some advitisers, which suited very well with the theme and philosophy of my blog and thus accepted the same. So, thanks to all my visitors, now my blog has earned its first income in the form of advertising.

Find all the missing paths in the PATH variable in bash script

Here is a simple script that will list out all the paths in the PATH variable that do not exist.

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      #!/bin/bash -<br /> #===============================================================================<br /> #<br /> #          FILE:  wrong_path.sh<br /> #<br /> #         USAGE:  ./wrong_path.sh<br /> #<br /> #   DESCRIPTION:  Show Directories in the PATH Which does NOT Exist<br /> #<br /> #       OPTIONS:  ---<br /> #  REQUIREMENTS:  ---<br /> #          BUGS:  ---<br /> #         NOTES:  ---<br /> #        AUTHOR:  Amit Agarwal (AKA), amit.agarwal@amit-agarwal.co.in<br /> #       COMPANY:  Individual<br /> #       VERSION:  1.0<br /> #       CREATED:  09/20/2009 09:15:48 AM IST<br /> #      REVISION:  ---<br /> #===============================================================================<br /> <br /> set -o nounset                              # Treat unset variables as an error<br /> <br /> (IFS=:;for p in $PATH; do test -d $p || echo $p; done)
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