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.

This is a quick line to stream in the latest offerings of your favorite netcasts/podcasts. You will need to have a file named netcast.txt in the directory you run this from. This file should have one and only one of your netcast's/podcst's url per line.

When run the line grabs the offering on the top of the netcast/podcast stack and end it over , quietly, to vlc.

Since I move around computers during the day I wanted an easy way to listen to my daily dose of news and such without having to worry about downloading to whatever machine I am on. This is just a quick grab and stream of whats current.

Future plans... have the list of netcasts be read from the web. possibly an rss or such. I use greader so there might be a way to use it as the source so as not to have to muck with multiple lists

Finds comments in jpg files, but I can't figure out how to exclude (in output) files without comments.

This command delete all the empty lines (include the lines with space) from a file.

g = global command

\S = non-whitespace character; !\S the opposite

d = delete a range

The same as typing 'less filename' then 'G' or '>' or the END key. Comes in handy with shell scripts or aliases:

alias weblog='less +G /var/log/httpd/access_log'

alias errlog='less +G /var/log/httpd/error_log'

Needed to get the Mac of various devices on a solaris box, but didn't have root. This command used awk to display the Network device, the IP, and the MAC a line at a time.

opens a "hidden" remote shell (login will not appear in "last" for example).

This is not really hidden, because the login will be shown in auth.log and the process is visible anyways.

ssh -T = Disable pseudo-tty allocation.

bash -i = interactive shell

You can use multiple field separators by separating them with | (=or).

This may be helpful when you want to split a string by two separators for example.

#echo "one=two three" | awk -F "=| " {'print $1, $3'}

one three

Place the line above in your ~/.bahsrc file. Now every time you issue the 'vb' command, you invoke the vim editor to edit it, then source it so the changes take effect immediately.

Notes:

* This mechanism is not working well if your .bashrc contains commands that should not be sourced more than once.

* This trick also work for your csh or tclsh users: place the following line in your ~/.cshrc file:

alias vc 'vim ~/.cshrc; source ~/.cshrc

Thank you adzap for pointing out the missing quote

On command mode in Vim you can save parts of the current buffer in another file.

* The 'n' value represents the first line of the new file.

* The 'm' value represents the last line of the new file.

* newfile.txt is the newfile.

The results are similar to this command in perl:

Immediately after installing things into your PATH (e.g. under /usr/bin), currently open shells cannot find them ("zsh: command not found"). Use rehash to get the shell to rescan available executables.

Discovering all executables on your system that can be run as another user, especially root, is critical for system security. The above command will find those files with have SUID or SGID bits set and are owned by the root user or group.

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.

Just waste some resources in a philosophical way

To connect to the shell run:

Launch a command from within a manpage, vim style. This is rather trivial, but can be very useful to try out the functions described in a manpage without actually quitting it (or switching to another console/screen/...).

Rather than typing out all 10 files, you can use brace expansion to do the trick for you. This is useful for backup files, numbered files, or any files with a repeating pattern. Gives more control than 'rm file*' as I might want to keep others around.

When downloading RPMs from the Internet, you don't have to 'rpm -i' or 'rpm -U' to install the package. Especially, if the package has dependencies. If you have YUM setup to access an RPM repository, this command will install the downloaded package, then any dependencies through YUM that it relies on. Very handy on RPM-based systems.

In this case, I'm keeping an eye on /var/log/messages, but of course any file will do. When I'm following a file, I generally don't want to see anything other than what has been added due to the command or service I've executed. This keeps everything clean and tidy for troubleshooting.