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determine if tcp port is open
for udp nmap -sU -p 80 hostname

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"

Find all files under a certain directory /home that have a certain suffix at the end of the file name. Show the file and rename them to remove the suffix.

analyze traffic remotely over ssh w/ wireshark
Please check out my blog article on this for more detail. http://jdubb.net/blog/2009/08/07/monitor-wireshark-capture-real-time-on-remote-host-via-ssh/

Create a new file

Close a hanging ssh session
~ is the ssh control character. If you type it after a newline, you can example force close the ssh session. , ~, then . If you want more info, type ~? when you are connecting using ssh. Very useful to kill of any hanging ssh sessions when nothing else works.

Quick way to sum every numbers in a file written line by line
If you have a file full of numbers written line by line, you can sum every line to get the total. With a file like this: 3443535 9878977 67554 987798 232324 you will got: 14610188

list block devices
Shows all block devices in a tree with descruptions of what they are.

Remove security limitations from PDF documents using ghostscript (for Windows)
#4345 also works under windows

Move a folder and merge it with another folder
This will move a folder and merge it with another folder which may contain duplicates. Technically it's just creating hardlinks of everything in the folder, and after it's done, delete the source (with rm -r source/ ) to complete the move. This is much faster than, for example, using rsync to merge folders which would actually copy the entire contents and so for a lot of files would take much longer. This uses macutils gcp port of cp so it can be used on osx/MacOS. If using in linux or some unix where cp includes the ability to create links with -l you can just use cp instead of gcp.


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