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find out how many days since given date
Exactly the same number of characters, exactly the same results, but with bc

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).

Route outbound SMTP connections through a addtional IP address rather than your primary

Add existing user to a group

Watch RX/TX rate of an interface in kb/s
Just a simple way without the need of additional tools. Of course, replace eth0 with your IF.

Find an installed app

escape any command aliases
e.g. if rm is aliased for 'rm -i', you can escape the alias by prepending a backslash: rm [file] # WILL prompt for confirmation per the alias \rm [file] # will NOT prompt for confirmation per the default behavior of the command

show framebuffer console modes to use in grub vga option
look at /boot/grub/menu.lst for somethig like: ## additional options to use with the default boot option, but not with the ## alternatives ## e.g. defoptions=vga=791 resume=/dev/hda5 ## defoptions=vga=795 # defoptions=vga=873 ## altoption boot targets option ## multiple altoptions lines are allowed ## e.g. altoptions=(extra menu suffix) extra boot options ## altoptions=(recovery) single # altoptions=(verbose mode) vga=775 debug # altoptions=(console mode) vga=ask # altoptions=(graphic mode) quiet splash # altoptions=(recovery mode) single vga=(decimal value) is framebuffer mode

FizzBuzz in one line of Bash
The (in)famous "FizzBuzz" programming challenge, answered in a single line of Bash code. The "|column" part at the end merely formats the output a bit, so if "column" is not installed on your machine you can simply omit that part. Without "|column", the solution only uses 75 characters. The version below is expanded to multiple lines, with comments added. for i in {1..100} # Use i to loop from "1" to "100", inclusive. do ((i % 3)) && # If i is not divisible by 3... x= || # ...blank out x (yes, "x= " does that). Otherwise,... x=Fizz # ...set x to the string "Fizz". ((i % 5)) || # If i is not divisible by 5, skip (there's no "&&")... x+=Buzz # ...Otherwise, append (not set) the string "Buzz" to x. echo ${x:-$i} # Print x unless it is blanked out. Otherwise, print i. done | column # Wrap output into columns (not part of the test).

Update program providing java on Debian
Lets you set all the java alternatives at once to a matching version. Also has options for just changing the jre or the plugin.


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