Taken from http://www.earthinfo.org/linux-disk-usage-sorted-by-size-and-human-readable/

somewhat faster version to see the size of our directories. Size will be in Kilo Bytes. to view smallest first change '-k1nr' to '-k1n'.

This commands will make it easier to select only common items between two files being compared. If your lines start with things other than lowercase a-z, adjust this Regex appropriately. Number of lines in the output has been set to no more than 10000, and should be adjusted as needed.

This set of commands was very convenient for me when I was preparing some xml files for typesetting a book. I wanted to check what styles I had to prepare but coudn't remember all tags that I used. This one saved me from error-prone browsing of all my files. It should be also useful if one tries to process xml files with xsl, when using own xml application.

This appends a random number as a first filed of all lines in SOMEFILE then sorts by the first column and finally cuts of the random numbers.

find largest file in /var

This command might not be useful for most of us, I just wanted to share it to show power of command line.

Download simple text version of novel David Copperfield from Poject Gutenberg and then generate a single column of words after which occurences of each word is counted by sort | uniq -c combination.

This command removes numbers and single characters from count. I'm sure you can write a shorter version.

This command list and sort files by size and in reverse order, the reverse order is very helpful when you have a very long list and wish to have the biggest files at the bottom so you don't have scrool up.

The file size info is in human readable output, so ex. 1K..234M...3G

Tested with Linux (Red Hat Enterprise Edition)

If you're like me and want to keep all your music rated, and you use xmms2, you might like this command.

I takes 10 random songs from your xmms2 library that don't have any rating, and adds them to your current playlist. You can then rate them in another xmms2 client that supports rating (I like kuechenstation).

I'm pretty sure there's a better way to do the grep ... | sed ... part, probably with awk, but I don't know awk, so I'd welcome any suggestions.

Here is a command line to run on your server if you think your server is under attack. It prints our a list of open connections to your server and sorts them by amount.

BSD Version:

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

This command checks for the number of times when someone has tried to login to your server and failed. If there are a lot, then that user is being targeted on your system and you might want to make sure that user either has remote logins disabled, or has a strong password, or both. If your output has an "invalid" line, it is a summary of all logins from users that don't exist on your system.

Very useful when you need disk space. It calculates the disk usage of all files and dirs (descending them) located at the current directory (including hidden ones). Then sort puts them in order.

Useful to check DDoS attacks on servers.