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Create a 100MB file for testing transfer speed

One line Perl Script to determine the largest file sizes on a Linux Server
This one line Perl script will display the smallest to the largest files sizes in all directories on a server.

Replaces a color in a PDF document, useful for removing a dark background before printing.
The pdf is first converted to a bitmap, so change "-density" to match your printer resolution. Also be careful about the RAM required. In this example rgb(0,0,0) is replaced by rgb(255,255,255), change to suit your needs.

using tee to echo to a system file with sudo privileges
We sometimes need to change kernel parameters by echoing the file . This needs root privilege and if we do it using sudo like this , it fails $ sudo echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor -bash: /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor: Permission denied We can achieve this with the tee command by just doing sudo without logging as root user http://www.zaman4linux.in/2010/09/using-tee-to-echo-to-system-file-with.html

Find the package that installed a command

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" }

Set laptop display brightness
Run as root. Path may vary depending on laptop model and video card (this was tested on an Acer laptop with ATI HD3200 video). $ cat /proc/acpi/video/VGA/LCD/brightness to discover the possible values for your display.

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

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 nifty overview of the hardware in your computer
After the command is done, open the html file in a browser


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