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Quick plotting of a function
The arguments of "seq" indicate the starting value, step size, and the end value of the x-range. "awk" outputs (x, f(x)) pairs and pipes them to "graph", which is part of the "plotutils" package.

Cut out a piece of film from a file. Choose an arbitrary length and starting time.
With: -vcodec, you choose what video codec the new file should be encoded with. Run ffmpeg -formats E to list all available video and audio encoders and file formats. copy, you choose the video encoder that just copies the file. -acodec, you choose what audio codec the new file should be encoded with. copy, you choose the audio encoder that just copies the file. -i originalfile, you provide the filename of the original file to ffmpeg -ss 00:01:30, you choose the starting time on the original file in this case 1 min and 30 seconds into the film -t 0:0:20, you choose the length of the new film newfile, you choose the name of the file created. Here is more information of how to use ffmpeg: http://www.ffmpeg.org/ffmpeg-doc.html

Directory bookmarks
pushd and popd are your friends, but sometimes they're just incompatible with the way one works... Two shell functions: bm bookmarkname - "bookmarks" the current directory, just 'cd $BMbookmarkname' to return to it. forget bookmarkname - unsets the 'bookmarkname' variable. It isn't mandatory, they cease to exist when the session ends.

get stdout to variable and stdout at sametime
Sometimes you want to write the script output to stdout but you need to send it to email. If you use: $ var="$( ls / )"; $ echo -e "$var"; works but, you need to wait the script terminate to bufferize then print the output var; With this way, you can use/work/print the output before the variable receive all the output content, then after it you can use the variable for anything else, like send email.

Delete only binary files in a directory
Please note that binary file checking is NOT perfect. So, use it with caution. It does not delete hidden files whose name has a leading '.' character. And it regards an empty file as a binary file.

Change gnome-shell wallpaper

prints line numbers
the sed way to print line numbers

check open ports without netstat or lsof

prevent accidents while using wildcards
alternative for "echo rm *.txt". Just doubletab the command you are willing to use and it will show you the affected files.

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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