Shows all linked file and destinations. The 'ls -l' command lists the files in long (1 file per line) format, and the grep command displays only those lines that starts with an l (lower case L) -- a linked file.

Updated: Remove reference to hard links because this command does not apply to hard link as others kindly pointed out.

the -3 show the previous, current, and next month.

The whatis command displays a short description for the command you list on the command line. It is useful to quickly learn what a command does

the middle command between the ; and ; is the vi commands that insert that line into the last line of the file, the esc with the carets is literally hitting the escape key, you have to have the smbfs package installed to do it, I use it to access my iTunes music on my mac from my linux PC's with amarok so I can play the music anywhere in the house. among other things, it allows you to access the files on that share from your computer anytime you're on that network.

Allow to read password in a script without showing the password inserted by the user

List files above a given size threshold.

This is a very powerful command line tool to gather statistics for a Linux system.

http://dag.wieers.com/home-made/dstat/

Reads a username from

This command will display only the hosts that are active in the network.

These are simple shortcuts to pause and continue terminal output, works in most terminals and screen multiplexers like screen. You can use it to catch something if things change too fast, and scroll with Shift + PgUp PgDown. On linux console ScrollLock can also be used.

Echos the number of seconds from the current time till the specified time (Example in command is (2**31-1)) aka the Unix epoch. Just replace that number with the specified date (in seconds past Jan. 1st 1970) and it will return the seconds.

NOTE: Only works in bash

This will perform one of two blocks of code, depending on the condition of the first. Essentially is a bash terniary operator.

To tell if a machine is up:

Because of the bash { } block operators, you can have multiple commands

Tips:

Remember, the { } operators are treated by bash as a reserved word: as such, they need a space on either side.

If you have a command that can fail at the end of the true block, consider ending said block with 'false' to prevent accidental execution

Requires ImageMagick. Takes a screenshot 5 seconds after it's run and saves it as desktop_screenshot.jpg Particularly handy when made into a menu option or button.

You can use this to loop any command to periodically see the output.

Alternatively, you can put it in a simple shell script to save typing!

#/!bin/bash

while true; do $1; sleep $2; done;

But who knows to delete the rest of the lines?

I want only "string".

Com o fuser voce descobre quem esta ocupando o dispositivo.

Depois pode desativar o servico manualmente. Ou se necessario, matar o servico com Kill, usando o numero PID.

ex: kill -9 1768

fonte: http://www.vivaolinux.com.br/dica/Desmontando-um-dispositivo-ocupado

This simply pulls the password out of the database for the given mail name for ease of use in testing emails that you would not normally have access to.

It can resume a failed secure copy ( usefull when you transfer big files like db dumps through vpn ) using rsync.

It requires rsync installed in both hosts.

rsync --partial --progress --rsh=ssh $file_source $user@$host:$destination_file local -> remote

or

rsync --partial --progress --rsh=ssh $user@$host:$remote_file $destination_file remote -> local

Are there any creative pieces of music that can be created using beep and the shell? I'd love to hear it!

This starts an X server using Xvfb(1) (no graphics hardware required), then starts a VNC server on the display. Change :1 if there's a conflict with an existing display, and change 800x600x24 to suit your tastes (24 is the bit depth, 800x600 is the size). This command obviously requires X be installed, and also x11vnc(1); both are available via your favourite package manager. You can also use another VNC server of your choosing, as long as DISPLAY is set to the display of Xvfb(1). To change your desktop environment (the default is twm(1), which is rather fail), you can add it to your ~/.xinitrc file (see the startx(1) manpage for details).

pings a server once per second, and beeps when the server is unreachable.

Basically the opposite of:

which would beep when a server IS reachable.

You could also substitute beep with any command, which makes this a powerful alternative to ping -a:

which would output the date and time every sec until the ping failed, in which case it would echo.

Notes:

Requires beep package.

May need to run as root (beep uses the system speaker)

Tested on Ubuntu which doesn't have beep out of the box...