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commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

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Count number of bytes that are different between 2 binary files

Create an eicar.com test virus
Test whether real-time virus detection is working by running this command and checking for eicar.com in /tmp. Requires real-time scanning to be enabled and active on the /tmp directory. If scanning is active, the file should be quarantined/deleted (depending on your settings) moments after running this command. If not, the (harmless) test file should remain in your /tmp directory.

Find default gateway

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).

Count number of hits per IP address in last 2000 lines of apache logs and print the IP and hits if hits > 20

Print text string vertically, one character per line.

Rename files in batch

Create a listing of all possible permissions and their octal representation.

Remount a usb disk in Gnome without physically removing and reinserting
Remounts a usb disk /dev/sdb, without having to physically remove and reinsert. (Gnome desktop)

diff directories, quick cut and paste to view the changes
We use this to quickly highlight differences and provide a quick way to cut and paste the command to view the files using the marvellous vimdiff


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