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Rsync between two servers
copying files from one server to another using rysnc. Root access need to be allowed on the destination.

Safe Russian Roulette (only echo, don't delete files)
Shows "Bang!" in a chance of 1 out of 6, like in the original game with the gun (spin every round). Otherwise, echoes "Click...". If feeling brave you can also do: $[ $[ $RANDOM % 6 ] == 0 ] && echo 'Bang!' && a really killer command || echo 'Click...'

Print ASCII Character Chart
Prints out an ascii chart using builtin bash! Then formats using cat -t and column. The best part is: $ echo -e "${p: -3} \\0$(( $i/64*100 + $i%64/8*10 + $i%8 ))"; From: http://www.askapache.com/linux/ascii-codes-and-reference.html

Check a server is up. If it isn't mail me.
This version uses netcat to check a particular service.

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.

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)
Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

scan whole internet and specific port in humanistic time
apt-get install git gcc make libpcap-dev git clone https://github.com/robertdavidgraham/masscan cd masscan make install -pDm755 bin/masscan /usr/bin/masscan

list files recursively by size

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Renaming a file without overwiting an existing file name
Sometimes in a hurry you may move or copy a file using an already existent file name. If you aliased the cp and mv command with the -i option you are prompted for a confirmation before overwriting but if your aliases aren't there you will loose the target file! The -b option will force the mv command to check if the destination file already exists and if it is already there a backup copy with an ending ~ is created.


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