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Automagically update grub.conf labels after installing a new kernel
I like to label my grub boot options with the correct kernel version/build. After building and installing a new kernel with "make install" I had to edit my grub.conf by hand. To avoid this, I've decided to write this little command line to: 1. read the version/build part of the filename to which the kernel symlinks point 2. replace the first label lines of grub.conf grub.conf label lines must be in this format: Latest [{name}-{version/build}] Old [{name}-{version/build}] only the {version/build} part is substituted. For instance: title Latest [GNU/Linux-2.6.31-gentoo-r10.201003] would turn to title Latest [GNU/Linux-2.6.32-gentoo-r7.201004]"

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Create a persistent connection to a machine
Create a persistent SSH connection to the host in the background. Combine this with settings in your ~/.ssh/config: Host host ControlPath ~/.ssh/master-%r@%h:%p ControlMaster no All the SSH connections to the machine will then go through the persisten SSH socket. This is very useful if you are using SSH to synchronize files (using rsync/sftp/cvs/svn) on a regular basis because it won't create a new socket each time to open an ssh connection.

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

wc in perl

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

fuman, an alternative to the 'man' command that shows commandlinefu.com examples
Example: fuman sed

Rename many files in directories and subdirectories
This is probably overkill, but I have some issues when the directories have spaces in their names. The $ find . -type d -print0 | while read -d $'\0' dir; do xxx; done loops over all the subdirectories in this place, ignoring the white spaces (to some extend). $ cd "$dir"; echo " process $dir"; cd -; goes to the directory and back. It also prints some info to check the progress. $ find . -maxdepth 1 -name "*.ogg.mp3" -exec rename 's/.ogg.mp3/.mp3/' {} \; renames the file within the current directory. The whole should work with directories and file names that include white spaces.

Find the most recent snapshot for an AWS EBS volume
Uses the python-based AWS CLI (https://aws.amazon.com/cli/) and the JSON query tool, JQ (https://stedolan.github.io/jq/)

Rename all .jpeg and .JPG files to have .jpg extension
the "i" controls case sensitiveness. It's slightly inefficient since it uselessly renames .jpg to .jpg, but that's more than compensated by launching only one process instead of two, besides being shorter to write.


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