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AWK Calculator

List only directories, one per line
omit the 1 (one) if you don't need one-per-line

Getting started with tcpdump
At some point you want to know what packets are flowing on your network. Use tcpdump for this. The man page is obtuse, to say the least, so here are some simple commands to get you started. -n means show IP numbers and don't try to translate them to names. -l means write a line as soon as it is ready. -i eth0 means trace the packets flowing through the first ethernet interface. src or dst w.x.y.z traces only packets going to or from IP address w.x.y.z. port 80 traces only packets for HTTP. proto udp traces only packets for UDP protocol. Once you are happy with each option combine them with 'and' 'or' 'not' to get the effects you want.

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

find the biggest files recursively, no matter how many
This command will find the biggest files recursively under a certain directory, no matter if they are too many. If you try the regular commands ("find -type f -exec ls -laSr {} +" or "find -type f -print0 | xargs -0 ls -laSr") the sorting won't be correct because of command line arguments limit. This command won't use command line arguments to sort the files and will display the sorted list correctly.

Convert mkv to SVCD/DivX
ffmpeg supports mkv

Record a screencast and convert it to an mpeg
Grab X11 input and create an MPEG at 25 fps with the resolution 800x600

Print current runlevel
Prints current runlevel and system start time. On older systems it also shows the last init state. Pretty useful on remote systems, pretty useless on local ones :)

Join the content of a bash array with commas
This type of join is clearly documented in the bash manual. Only the first character of IFS is used for the delimiter.

convert vdi to vmdk (virtualbox hard disk conversion to vmware hard disk format)
Converts a .vdi file to a .vmdk file for use in a vmware virtual machine. The benefit: using this method actually works. There are others out there that claim to give you a working .vmdk by simply using the qemu-img command alone. Doing that only results in pain for you because the .vmdk file will be created with no errors, but it won't boot either. Be advised that these conversions are very disk-intensive by nature; you are probably dealing with disk images several gigabytes in size. Once finished, the process of using the new .vmdk file is left as an exercise to the reader.


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