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Functions to display, save and restore $IFS
You can display, save and restore the value of $IFS using conventional Bash commands, but these functions, which you can add to your ~/.bashrc file make it really easy. To display $IFS use the function ifs shown above. In the sample output, you can see that it displays the characters and their hexadecimal equivalent. This function saves it in a variable called $saveIFS: $ sifs () { saveIFS=$IFS; } Use this function to restore it $ rifs () { IFS=$saveIFS; } Add this line in your ~/.bashrc file to save a readonly copy of $IFS: $ declare -r roIFS=$IFS Use this function to restore that one to $IFS $ rrifs () { IFS=$roIFS; }

run a command from within vi without exiting
":! ls -l " results in listing the files in the current directory. pressing "enter" will get you back into vi.

Database size
Mysql command to list the disk usage of the database

Day of the week of your birthday over the years.
Do you ever want to know which day of week was your birhday! Now you can check that with this command, just set your birh date at the beginning (My bday in the example) and the dates will be revealed. ;)

Copy your ssh public key to a server from a machine that doesn't have ssh-copy-id
If you use Mac OS X or some other *nix variant that doesn't come with ssh-copy-id, this one-liner will allow you to add your public key to a remote machine so you can subsequently ssh to that machine without a password.

Execute MySQL query send results from stdout to CSV
You can, of course, tell MySQL to output results to a file and dictate how to terminate lines, etc. But sometimes you don't have access to the file system MySQL is running on, complicating outputting your results to a CSV, necessitating either annoying hacks or this simple command :D

convert single digit to double digits
from 1.ogg 2.ogg 3.ogg 10.ogg 11.ogg to 01.ogg 02.ogg 03.ogg 10.ogg 11.ogg

Create a temporary file
To create directory, use: $ tempdir=$(/bin/mktemp -d)

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

Add "prefix" on a buch of files


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