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list unique file extensions recursively for a path, include extension frequency stats
Get the longest match of file extension (Ex. For 'foo.tar.gz', you get '.tar.gz' instead of '.gz')

Stop Flash from tracking everything you do.
Brute force way to block all LSO cookies on a Linux system with the non-free Flash browser plugin. Works just fine for my needs. Enjoy.

Compute the average number of KB per file for each dir
Shorter version using --tag

See non printable caracters like tabulations, CRLF, LF line terminators ( colored )
For fancier and cleaner output, try the following snippet : $ showendlines(){ while read i; do od --address-radix=n --width=$(wc -c

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Efficient count files in directory (no recursion)
$ time perl -e 'if(opendir D,"."){@a=readdir D;print $#a - 1,"\n"}' 205413 real 0m0.497s user 0m0.220s sys 0m0.268s $ time { ls |wc -l; } 205413 real 0m3.776s user 0m3.340s sys 0m0.424s ********* ** EDIT: turns out this perl liner is mostly masturbation. this is slightly faster: $ find . -maxdepth 1 | wc -l sh-3.2$ time { find . -maxdepth 1|wc -l; } 205414 real 0m0.456s user 0m0.116s sys 0m0.328s ** EDIT: now a slightly faster perl version $ perl -e 'if(opendir D,"."){++$c foreach readdir D}print $c-1,"\n"' sh-3.2$ time perl -e 'if(opendir D,"."){++$c foreach readdir D}print $c-1,"\n"' 205414 real 0m0.415s user 0m0.176s sys 0m0.232s

urldecoding
My version uses printf and command substitution ($()) instead of echo -e and xargs, this is a few less chars, but not real substantive difference. Also supports lowercase hex letters and a backslash (\) will make it through unescaped

To get the CPU temperature continuously on the desktop
There is no need for variables. I also added sleep to reduce cpu usage, however I didn't test it.

Check the age of the filesystem
Very useful set of commands to know when your file system was created.

Get list of servers with a specific port open
Change the -p argument for the port number. See "man nmap" for different ways to specify address ranges.


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