This is an extension of my last BASH post, Taking Control: More BASH Tips. In that post we discussed some of the control commands that are available for clearing the screen, searching the history and moving the cursor around. This time we are going to talk about modifying the text in the current command.

CTRL+_ or CTRL+-
Let’s start out with the thing that we all need sometimes, undo. Control and underscore or dash will undo the last control command done in bash. It WILL NOT undo the last command executed on the system. For example if you cut all of the text from the cursor to the beginning of the line but really ment to cut the last word you can use undo.

#I want to change badger to fox.
j2consulting:~ user1$ The quick brown badger jumps over the lazy dog.
#I hit CTRL+u instead of CTRL+w
j2consulting:~ user1$ jumps over the lazy dog.
#CTRL+- saves me from my mistake
j2consulting:~ user1$ The quick brown badger jumps over the lazy dog.

CTRL + u, CTRL + w, CTRL + k
As I showed in the previous example, you can remove text from the current command. Using these control commands you can delete text based on the current cursor position. Control and u will delete all of the text from the point of the cursor to the beginning of the command. Control and k will delete all of the test from the point of the cursor to the end of the command. Finally, control and w will delete the previous word in the command.

#I want to change badger to fox.
j2consulting:~ user1$ The quick brown badger jumps over the lazy dog.
#I move the cursor to the space between badger and jumps and then hit CTRL+w
j2consulting:~ user1$ The quick brown jumps over the lazy dog.
#Now I can add fox.
j2consulting:~ user1$ The quick brown fox jumps over the lazy dog.
#I don't like the end so I move the cursor to the space between fox and jumps and hit CTRL+k
j2consulting:~ user1$ The quick brown fox
#And now I change the ending.
j2consulting:~ user1$ The quick brown fox hides while the dog chases him.
#But now it's just wrong and I want to delete everything from the end to the beginning so I hit CTRL+u
j2consulting:~ user1$

CTRL + y
So you have just got done cutting all kinds of text, what is the next logical thing? Paste. Any of the text you cut using the previous 3 commands can be pasted into the line. Let’s switch the sentence around to put the dog first.

j2consulting:~ user1$ The quick brown fox jumps over the lazy dog.
#Putting my cursor on the . and hitting CTRL+w I cut the previous word.
j2consulting:~ user1$ The quick brown fox jumps over the lazy .
#Now I put my cursor between fox and jumps and hit CTRL+y
j2consulting:~ user1$ The quick brown foxdog jumps over the lazy .
#Now I put my cursor on the d in dog and hit CTRL+w
j2consulting:~ user1$ The quick brown dog jumps over the lazy .
#Finally I put my cursor on the . again and hit CTRL+y to paste the fox
j2consulting:~ user1$ The quick brown dog jumps over the lazy fox.

CTRL + t
It is a fairly common mistake to transpose two characters while typing. Control and t can help us quickly fix this by swapping the previous two characters.

j2consulting:~ user1$ Teh
#Oops, I ment to spell The, hit CTRL+t
j2consulting:~ user1$ The
#This can also work if you want to move the cursor to the mistake.
j2consulting:~ user1$ Teh quick brown fox jumps over the lazy dog.
#By placing the cursor between the h and q and hitting CTRL+t we can fix the mistake.
j2consulting:~ user1$ The quick brown fox jumps over the lazy dog.

By using the tricks in this and previous BASH posts you can significantly reduce the time it takes you to get things done. If you know of any other tricks I’d love to hear about them in the comments.

As a consultant who works with remote clients and, before that, a telecommuting systems engineer for companies who used linux I have often encountered the problem of collaborating inside of a remote client that does not have X and who’s only access is ssh. Servers with GUI interfaces like Windows or Mac OS X have a long history of tools to share the desktop with multiple users, oddly enough both are called Remote Desktop. Servers that only have a command line interface, like most linux servers, do not have such an obvious tool for sharing the terminal with another user. While bash and ssh can be manipulated to accomplish this, screen fills this roll nicely.

Screen allows you to create virtual terminals that you can detach from and attach to at will. Detaching from a screen will leave it running in the background. Attaching to it again allows you to keep executing commands where you were or see the current state of a process you left running. If you are the user who started the screen you can attach to a screen that is already attached to, this is is how the shared screen is accomplished.

To set it up, one user logs in to the server and, using su or sudo su, changes to either the second users account or an account that all parties can access. Next, start screen with the -S option and give it a meaningful name.

me@jjtest:~# sudo su – theOtherGuy
theOtherGuy@jjtest:~# screen -S blogTest

If screen is not installed, it is available as a package on most popular linux distributions. You are now in a screen session as theOtherGuy. Now just tell theOtherGuy to log in and that your screen is called blogTest and he will simply need to run screen with the -x option and give the screen name.

theOtherGuy@jjtest:~# screen -x blogTest

At this point you are both in the same screen session and can both interact with it. This is great for showing another user what kind of problems you may be having or how to do a certain process. It can also be used to accomplish remote pair programing on the remote system. And this doesn’t have to be limited to just two users, as long as someone can get to that system as that user they can join the screen as well.

Typing exit at this point will kill the screen and kick both of you out. If one user wants to leave but not kick the other person off the user just presses Ctrl+a and then d, this will detach you from the screen. Ctrl+a is the default hot key for activating screen commands. You can read more about the variety of command available on screen at this site or read abut it fully on the man page.

Screen can be used to do so much more than I’ve talked about here but it’s ability to facilitate the sharing of a terminal between users can be a life saver when you need it. It is not normally installed by default to may linux systems so you may have to install it or ask that it be installed.

This post originally written for my personal blog on June 14th 2009.

As a systems administrator in many mixed Windows and linux environments I have seen and made many of my own attempts at integrating the linux servers into the Windows Active Directory structure with mixed results. Linux registration and authentication inside of a Windows domain is akin to the bigfoot: some have claimed to see one, many have worked long hours to find them, no one can produce consistent results. Until now.

At the suggestion by a coworker I decided to give Likewise a try on my most recent attempt at bringing our linux servers into the windows domain. Skeptically I built a new CentOS 5.3 server and proceeded to follow the instructions for installing Likewise. The seemed too simple and with each step I waited for the fatal issue that would bring the test to it’s demise. Software installed, no issues. As I reviewed the instructions for adding the system to the domain and found that it only required one command and no further configuration of files I thought, “This is so going to fall on it’s face.” Command executed and I’m waiting, then it comes up on the screen: Success. Success? Really? I don’t believe it, I log onto the domain controller and there it is, right where new computers are supposed to go in the domain. I quickly flip over to the manual and look up how to authenticate for ssh, simple DOMAIN\\username@host, and give it the final test. Success. In the span of 15 minutes I was able to install the app, add my computer to the domain and authenticate against the domain. 15 more minutes and I was able to limit who could log in and give them sudo access. This is a huge win for any admin who deals with linux servers in a domain.

I’m still testing the limits of Likewise and I will say that it hasn’t been without it’s speed bumps but I plan on paying for a little support and getting the answers I need. Like may open source products, Likewise is making it’s money on support and by selling upgraded functionality. I applaud this model, allowing the flexibility of open source while still finding a way to pay for all that hard work. I will be continuing to test the limits of Likewise but as of now I am thoroughly impressed and will continue to use it.