When you've got a list of numbers each on its row, the ECHO command puts them on a simple line, separated by space. You can then substitute the spaces with an operator. Finally, pipe it to the BC program.

Useful when you have some wrong on a server (nfs freeze/ immortal process)

Create a bunch of random files with random binary content. Basically dd dumps randomly from your hard disk to files random-file*.

Display the amount of memory used by all the httpd processes. Great in case you are being Slashdoted!

slashdot.org webserver adds an X-Bender or X-Fry HTTP header to every response!

A common mistake in Bash is to write command-line where there's command a reading a file and whose result is redirected to that file.

It can be easily avoided because of :

1) warnings "-bash: file.txt: cannot overwrite existing file"

2) options (often "-i") that let the command directly modify the file

but I like to have that small function that does the trick by waiting for the first command to end before trying to write into the file.

Lots of things could probably done in a better way, if you know one...

Same as above but slooooow it down

Next time you are leaching off of someone else's wifi use this command before you start your bittorrent ...for legitimate files only of course.

It creates a hexidecimal string using md5sum from the first few lines of /dev/urandom and splices it into the proper MAC address format. Then it changes your MAC and resets your wireless (wlan0:0).

You got some results in two variables within your shell script and would like to find the differences? Changes in process lists, reworked file contents, ... . No need to write to temporary files. You can use all the diff parameters you'll need. Maybe anything like $ grep "^>"

is helpful afterwards.

This will create the file /tmp/pkgdetails, which will contain a listing of all the files installed on your RPM-based system (RedHat, Fedora, CentOS, etc). Useful should the RPM system/database become corrupted to find which package installed which files.

In Debian based distros, this command will list 'binutils' package details which contains 'nm' command. You can replace 'nm' to any other command.

Save the script as: sort_file

Usage: sort_file < sort_me.csv > out_file.csv

This script was originally posted by Admiral Beotch in LinuxQuestions.org on the Linux-Software forum.

I modified this script to make it more portable.

Infinitely plays beeps with sinusoidally changing sound frequency. Ideal for alarm on an event.

It's the same command as submitted, but first with a command to make all characters green. It's the only way it looked "matrix-like" on my gnome-terminal.

When you use a "for" construct, it cycles on every word. If you want to cycle on a line-by-line basis (and, well, you can't use xargs -n1 :D), you can set the IFS variable to .

This will create a permanent alias to colorize the search pattern in your grep output

Handy use of bc in the command line. No need to get 'into' the bc to perform calculations

Empties all files in /var/log over 5000k. Useful if /var goes crazy or if you just haven't cleaned up in a while.

Found this one little more for me. This one removes the perl dependency (from command 2535).

Source for command : http://www.earthinfo.org/linux-disk-usage-sorted-by-size-and-human-readable/

defines a handy function for quick calculations from cli.

once defined:

Skype has an internal regex which depicts the emoticons it supports. However you cannot simply search the binary file for it. This small 181 character line will do just that, provided skype is running. And of course, only works in linux.

When plumbers use pipes, they sometimes need a T-joint. The Unix equivalent to this is 'tee'. The -a flag tells 'tee' to append to the file, rather than clobbering it.

Tested on bash and tcsh.

Set an alarm to starts in specific time.

get desired info from machine and pipe it txt file.