It extracts X number of lines from file1 and dumps them to file2.Using grep with the empty string '' extracts the complete lines (i.e. no filtering takes place) and the -m flag indicates how many lines to extract out from the given file. Then using the redirect > operator we send the extracted lines to a new file.

The brace expansion also allows you to count backward:

for i in {15..1}; do echo $i; done

You can also use this construct to create new file or new directory:

mkdir dir{1..3} # Same as mkdir dir1 dir2 dir3

This loops through all tables and changes their collations to UTF8. You should backup beforehand though in case some data is lost in the process.

Useful for monitoring both MySQL and the server load at the same time.

Displays the duplicated lines in a file and their occuring frequency.

Autojump is cd command that learns. More info: http://wiki.github.com/joelthelion/autojump

Show the number of failed tries of login per account. If the user does not exist it is marked with *.

Replace "url" with the correct address of what your're downloading. Replace 01:00 with what time you want. (24-hour clock).

Displays all information about your battery. for just capacity, try replacing cat with

Battery number might be BAT0 instead of BAT1. Just run

and find out what folder is in that directory and replace that name with BAT1

I often deal with long file names and the 'ls -l' command leaves very little room for file names. An alternative is to use the -h -o and -g flags (or together, -hog).

* The -h flag produces human-readable file size (e.g. 91K instead of 92728)

* The -o suppresses the owner column

* The -g suppresses the group column

Since I use to alias ll='ls -l', I now do alias ll='ls -hog'

time read -sn1 (s:silent, n:number of characters. Press any character to stop)

This command will grep the entire directory looking for any files containing the list of files. This is useful for cleaning out your project of old static files that are no longer in use. Also ignores .svn directories for accurate counts. Replace 'static/images/' with the directory containing the files you want to search for.

You need curl.. and a Mac of course.

This is a (last resort) way to automate applications that provide no other ways for automation, it would send 'Hello world' to the currently active window. See the manpage (and the -text and -window entries) for how to send special characters and target specific windows.

An example:

Using xwininfo, I get the id of my XPlanet background window:

alanceil@kvirasim:19:51:0:~> xwininfo

xwininfo: Please select the window about which you

would like information by clicking the

mouse in that window.

xwininfo: Window id: 0x3600001 "Xplanet 1.2.0"

Absolute upper-left X: 0

(..etc..)

Now I use xvkbd to tell it to close itself:

xvkbd -xsendevent -window 0x3600001 -text "Q"

Obviously, the best way is to put these commands in a shellscript - just make sure to include a short sleep (sleep .1 should suffice) after each xvkbd call, or some programs will become confused.

If you have a JAR that is not in a central Maven repository this will add it to your repository.

This lets you use your favorite vi edit keys to navigate your term.

To set it permanently, put "set editing-mode vi" in your ~/.inputrc or /etc/inputrc.

If you would like to edit a previous command, which might be long and complicated, you can use the fc (I think it stands for fix command). Invoke fc alone will edit the last command using the default editor (specified by $FCEDIT, $EDITOR, or emacs, in that order). After you make the changes in the editor, save and exit to execute that command. The fc command is more flexible than what I have described. Please 'man bash' for more information.

CDPATH tells the cd command to look in this colon-separated list of directories for your destination. My preferred order are 1) the current directory, specified by the empty string between the = and the first colon, 2) the parent directory (so that I can cd lib instead of cd ../lib), 3) my home directory, and 4) my ~/projects directory.

Watch the number of packets/bytes coming through the firewall. Useful in setting up new iptables rules or chains. Use this output to reorder rules for efficiency.

I had a hard time in finding the correct settings to get reasonable output from a coin selector which sends its data over a serial line. In the end, minicom came to the rescue and pointed me on the right track.

So, if you need to do something similar, these settings may help you.

Replace ttyUSB0 with your device file, 9600 with your baud rate, 5 with your read timeout (10ths of a second), and 1 with the minimum numbers of characters you want to read.

You can then open the device file like you are used to do, example:

Replace the words between BEGIN and END.

Particularly useful if you're mounting different drives, using the following command will allow you to see all the filesystems currently mounted on your computer and their respective specs with the added benefit of nice formatting.