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create random numbers within range for conjob usage
if you need to install cron jobs in a given time range.

Remove all zero size files from current directory (not recursive)

Show sorted list of files with sizes more than 1MB in the current dir

send echo to socket network
Using netcat, usuallly installed on debian/ubuntu. Also to test against a sample server the following two commands may help echo got milk? | netcat -l -p 25 python -c "import SocketServer; SocketServer.BaseRequestHandler.handle = lambda self: self.request.send('got milk?\n'); SocketServer.TCPServer(('0.0.0.0', 25), SocketServer.BaseRequestHandler).serve_forever()"

processes per user counter
awk is evil!

Quicker move to parent directory
Alias two dots to move to parent directory. Put it into your .bashrc or .profile file.

Print diagram of user/groups
Parses /etc/group to "dot" format and pases it to "display" (imagemagick) to show a usefull diagram of users and groups (don't show empty groups).

Block all IPv4 addresses that has brute forcing our ssh server
For ipv6 use: grep -oE "\b([0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}\b"

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"

a function to find the fastest DNS server
http://public-dns.info gives a list of online dns servers. you need to change the country in url (br in this url) with your country code. this command need some time to ping all IP in list.


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