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Insert a line at the top of a text file without sed or awk or bash loops
Yet another way to add a line at the top a of text file with the help of the tac command (reverse cat).

a function to find the fastest DNS server
http://public-dns.info gives a list of online dns servers. you need to change the country in url (br in this url) with your country code. this command need some time to ping all IP in list.

Increase SCT of external USB disk enclosure to one hour.
So I had this 2TB Seagate external disk/USB enclosure which by default would spin-down its internal drive (it enters a standby mode) after four minutes of inactivity.. Spinning-up the inactive drive was an annoying delay when accessing files and also it severely interfered with NFS.. SCT stands for "Standby Condition Timer". To completely disable SCT: $ sdparm --clear STANDBY -6 /dev/sdb To return to original (default) SCT settings: $ sdparm -D -p 0x1a -6 /dev/sdb To verify the settings (before and after): $ sdparm -a /dev/sdb No need for vendor-provided MSWIN tools, etc.

Write comments to your history.
A null operation with the name 'comment', allowing comments to be written to HISTFILE. Prepending '#' to a command will *not* write the command to the history file, although it will be available for the current session, thus '#' is not useful for keeping track of comments past the current session.

Capitalize first letter of each word in a string - A ruby alternative
"-n" loops around ; "-e" executes the given quoted string ; "$_" is the current line ; "split" creates an array on white space; each item of the array is "collected" to be then "capitalized" ; the array is "joined" back into a string.

make computer speaking to you :)
you can listen to your computer, but don't be carried away

Find the package that installed a command

convert ascii string to hex
just a bit simpler

Returns the number of cores in a linux machine.
Original article in http://www.howtogeek.com/howto/ubuntu/display-number-of-processors-on-linux/

Get all files of particular type (say, PDF) listed on some wegpage (say, example.com)
See man wget if you want linked files and not only those hosted on the website.


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