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Generat a Random MAC address

Apply permissions only to files
To apply only to dirs: $ chmod 755 $(find . -type d) Use -R parameters for recursive walk.

List top 20 IP from which TCP connection is in SYN_RECV state
List top 20 IP from which TCP connection is in SYN_RECV state. Useful on web servers to detect a syn flood attack. Replace SYN_ with ESTA to find established connections

Determine whether a CPU has 64 bit capability or not
Check if you have 64bit by looking for "lm" in cpuinfo. lm stands for "long mem". This can also be used without being root.

convert wav files to flac
cd to the folder containing the wav files, then convert them all to flac. yeah baby! in ubuntu, to get the flac program just: sudo apt-get install flac flac file input formats are wav, aiff, raw, flac, oga and ogg

know the current running shell (the true)
Return the current shell. It is better than print $SHELL which can sometimes return a false value.

temporarily override alias of any command
say, someone has aliased ls to 'ls --color=always' and you want to temporarily override the alias (it does not override functions)

Remove ( color / special / escape / ANSI ) codes, from text, with sed
Remove ( color / special / escape / ANSI ) codes, from text, with sed Credit to the original folks who I've copied this command from. The diff here is: Theirs: [m|K] Theirs is supposed to remove \E[NUMBERS;NUMBERS[m OR K] This statement is incorrect in 2 ways. 1. The letters m and K are two of more than 20+ possible letters that can end these sequences. 2. Inside []'s , OR is already assumed, so they are also looking for sequences ending with | which is not correct. This : [a-zA-Z] This resolves the "OR" issue noted above, and takes care of all sequences, as they all end with a lower or upper cased letter. This ensures 100% of any escape code 'mess' is removed.

Convert all files *.mp4 to *.mpeg using ffmpeg (Windows Cmd line)
Note: %~nI expands %I to a file name only (cf. http://technet.microsoft.com/en-us/library/bb490909.aspx)

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"


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