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Download YouTube Videos using wget and youtube-dl and just using the video link
in place of "output-filename.mp4" put the name you want the file to be named with. in place of "youtube-video-link" put the link of the Video page eg: http://www.youtube.com/watch?v=AclA-7YntvE in place of "format-number" put the number of the file format you would like How to get the "format-number" to get format number type in below command before running this command $ youtube-dl -F "youtube-video-link" and it will list all the available formats with the format number, like to download in 360p mp4 use the number "18" To automatically let it fetch the best quality available just remove the -f "format-number" and you are good to go.

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"

See a full list of compiler defined symbols
From http://lists.debian.org/debian-devel/2001/01/msg00971.html .

count the number of specific characters in a file or text stream
In this example, the command will recursively find files (-type f) under /some/path, where the path ends in .mp3, case insensitive (-iregex). It will then output a single line of output (-print0), with results terminated by a the null character (octal 000). Suitable for piping to xargs -0. This type of output avoids issues with garbage in paths, like unclosed quotes. The tr command then strips away everything but the null chars, finally piping to wc -c, to get a character count. I have found this very useful, to verify one is getting the right number of before you actually process the results through xargs or similar. Yes, one can issue the find without the -print0 and use wc -l, however if you want to be 1000% sure your find command is giving you the expected number of results, this is a simple way to check. The approach can be made in to a function and then included in .bashrc or similar. e.g. $ count_chars() { tr -d -c "$1" | wc -c; } In this form it provides a versatile character counter of text streams :)

Backup all MySQL Databases to individual files

Find default gateway

find and reduce 8x parallel the size of JPG images without loosing quality via jpegoptim

locate bin, src, and man file for a command

Copy all shared libraries for a binary to directory
When working with jailed environments you need to copy all the shared libraries to your jail environment. This is done by running ldd on a binary which needs to run inside the jail. This command will use the output from ldd to automatically copy the shared libraries to a folder of your choice.

Print process run time, average CPU usage, and maximum memory usage on exit
Bash has a built-in time command which provides less functionality than the real time command. Thus we reference /usr/bin/time directly. Since the command isn't very easy to remember you could alias it to something like "cputime" or even just "time".


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