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gets your public IP address

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"

List 10 largest directories in current directory
Directories listed in human-readable format

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" }

user 'tr' to convert mixed case in a file to lower case
convert mixed case in a file to lower case

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

Remove empty directories
You can also use, $ find . -depth -type d -exec rmdir {} \; 2>/dev/null

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"

Scale,Rotate, brightness, contrast,...with Image Magick
$rotate: the rotate angle $width, $height: width and height to scale to $birghtness: change brighness

Retry the previous command until it exits successfully


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