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Turn On/Off Keyboard LEDs via commandline
Usefull as a light blink to remember events, mails, intrusions, etc... yet another output Since nobody ever uses the scroll lock function... Usefull to interface a linux system with some hardware, for example, opto interfacing the keyboard led to a relay to remotely reset, etc. ( a simple LDR glued over the LED will do the trick ) xset led 3 turns on the third led, ie, Scroll lock xset -led 3 turns it off xset led 1 turns on Numerical Lock led ( doesn t work on all computer ) xset led 2 turns on Caps Lock led ( idem ) Using it as a reset watchdog, the relay expected light pulses. Shall the computer hangs, the relay releases and reset the machine ( discharge of a capacitor ) ;-)

Alias TAIL for automatic smart output
Run the alias command, then issue $ps aux | tail and resize your terminal window (putty/console/hyperterm/xterm/etc) then issue the same command and you'll understand. $ ${LINES:-`tput lines 2>/dev/null||echo -n 12`} Insructs the shell that if LINES is not set or null to use the output from `tput lines` ( ncurses based terminal access ) to get the number of lines in your terminal. But furthermore, in case that doesn't work either, it will default to using the default of 80. The default for TAIL is to output the last 10 lines, this alias changes the default to output the last x lines instead, where x is the number of lines currently displayed on your terminal - 7. The -7 is there so that the top line displayed is the command you ran that used TAIL, ie the prompt. Depending on whether your PS1 and/or PROMPT_COMMAND output more than 1 line (mine is 3) you will want to increase from -2. So with my prompt being the following, I need -7, or - 5 if I only want to display the commandline at the top. ( http://www.askapache.com/linux/bash-power-prompt.html ) 275MB/748MB [7995:7993 - 0:186] 06:26:49 Thu Apr 08 [askapache@n1-backbone5:/dev/pts/0 +1] ~ $ In most shells the LINES variable is created automatically at login and updated when the terminal is resized (28 linux, 23/20 others for SIGWINCH) to contain the number of vertical lines that can fit in your terminal window. Because the alias doesn't hard-code the current LINES but relys on the $LINES variable, this is a dynamic alias that will always work on a tty device.

A little bash daemon =)
A little bash daemon

find all active IP addresses in a network
You send a unicast ICMP packet to each host. Many firewalls will drop that ICMP. However, in order to send the ICMP, you'll have first done an ARP request and the remote machine is unlikely to ignore that, so the computer will be in your ARP table.

Print the IPv4 address of a given interface

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"

grep certain file types recursively

Show the last 20 sessions logged on the machine
change 20 by the number of sessions you want to know (20 it's fair enough)

check open ports without netstat or lsof


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