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Remove old unused kernels from Red Hat Enterprise Linux 5 & Fedora 12/13
Install using yum install yum-utils Options include: --oldkernels Remove old kernel and kernel-devel packages --count=KERNELCOUNT Number of kernel packages to keep on the system (default 2) use package-cleanup --help for a complete list

The Hidden PS
While going through the source code for the well known ps command, I read about some interesting things.. Namely, that there are a bunch of different fields that ps can try and enumerate for you. These are fields I was not able to find in the man pages, documentation, only in the source. Here is a longer function that goes through each of the formats recognized by the ps on your machine, executes it, and then prompts you whether you would like to add it or not. Adding it simply adds it to an array that is then printed when you ctrl-c or at the end of the function run. This lets you save your favorite ones and then see the command to put in your .bash_profile like mine at : http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html Note that I had to do the exec method below in order to pause with read. t () { local r l a P f=/tmp/ps c='command ps wwo pid:6,user:8,vsize:8,comm:20' IFS=' '; trap 'exec 66

pushd rotates the stack so that the second directory comes at the top.
'pushd +1' is equivalent to 'pushd'. Can be 'pushd +3' or more generaly 'pushd +N'. Can also be 'pushd -N'. More description in 'man bash'.

Verify if ntpd is working properly
Used to verify if Network Time Protocol daemon is working properly.

python - covert image to base64 string for data URI use
useful if you are using lots of data URI's in your css files

Use AWS CLI and JQ to get a list of instances sorted by launch time
Use the AWS CLI tools to generate a list instances, then pipe them to JQ to show only their launch time and instance id. Finally use sort to bring them out in runtime order. Find all those instances you launched months ago and have forgotten about.

get colorful side-by-side diffs of files in svn with vim
This will diff your local version of the file with the latest version in svn. I put this in a shell function like so: $svd() { vimdiff

Find usb device
I often use it to find recently added ou removed device, or using find in /dev, or anything similar. Just run the command, plug the device, and wait to see him and only him

print/scan lines starting at record ###
Useful for finding newly added lines to a file, tail + can be used to show only the lines starting at some offset. A syslog scanner would look at the file for the first time, then record the end_of_file record number using wc -l. Later (hours, days), scan only at the lines that were added since the last scan.

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" }


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