Hello Dave. I need a Bash shell script that creates a directories with the group names automatically when user logs in to the system, in their home directory.

For example, user "sandy" might have the following set of groups from the 'id' command:

uid=10002(sandy) gid=119(rtkit) groups=119(rtkit),10001(admin),10003(pr007drdl)

and the directories "rtkit", "admin" and "pr007drdl" should then be created. How do I do it?

As part of reinventing myself professionally, I want to be a system administrator with networking knowledge. I thought that was the typical thing to do, most likely something windows related with their boatloads of certifications not including experience needed to get into the work field.

I talked to someone that has been in the role of system administrator, however, and he actually pointed me in a different direction: He dissed Windows...

If I really wanted to learn something that's been around for decades with little changes, and in great demand then he said I should learn the foundation of UNIX, as everyone in the world needs a UNIX Admin. The market's saturated with sys admin in windows/help desk/supports etc. and if you wanted to work in another country, I'd have no issues with language, computer wise. And that I can work in any type of industry as UNIX is the main backbone for 90% of commercial organizations.

What do you think, Dave? What's the core skillset and training needed to be a successful system administrator in the next decade?

I'm confused: on my Mac when I go to install new software sometimes I just drag and drop it and everything's fine, but other times I get "item in use" errors and have to reboot before I can install the new app. What's up with that?

If you're running an online business like I am, there are times when you need to connect and log in to the server to tweak or check things. It can't be helped and while the Cpanel solution and related are often splendid, sometimes I just like to get bits all over my hands as I "go old school" on my server and use a command line.

In those instances there's a nice solution on the Mac called "Terminal", included with Mac OS X, and there's a rudimentary terminal window app for Windows too, but once you move onto mobile devices of any nature, nothing's available.

That's why I was so interested in iSSH [iTunes link], a low-cost iPad application that lets me connect directly to my Web server via a secure, encrypted connection (SSH = secure shell, it's the secure alternative to "telnet') from my iPad and, in case of a crisis, even my iPhone.

As part of some user interface testing I'm involved with on an Ubuntu Linux system, I find myself frequently having to rename groups of files in a sequential manner. That is, I'll have files like "output mm-dd-yyyy at hh:mm:ss" and need to rename them to "testrun-xx-file-yy". Is there any way to automate this so I don't have to go crazy typing?

Dave, can you tell me, how come I enjoy shell programming more than other types of programming (Javascript, Java or C)?

Dave, I know how to check for free disk space on Windows XP, but how do I check for the amount of free disk space available on a machine running Linux (CentOS, Fedora, Red Hat, Ubuntu, etc.)?

I have a Virtual Private Server or a dedicated server running Linux, but I'm not sure which version of Linux (Fedora, CentOS, Debian, etc.) the server is running. How do I find out?

I have Mac OS X 10.5.8. When I try to change my unix shell prompt by putting the line:

  export PS1='mac> '

into my .bash_profile, the prompt is changed but the cursor is in the first column (over the "m" of my prompt) and any typing overwrites the prompt.

I move around quite a bit as a road warrior and though I don't often need to print, sometimes being able to produce a hard copy is definitely helpful. Problem is, I don't want to bother people in different temporary offices with configuration details: I'm running Mac OS X Snow Leopard on my MacBook Pro, is there some easy way to add printers on the go?

We have a situation where we need to keep a ZIP archive of some data files available on our Ubuntu Linux server so that our satellite offices can grab the information through slower data lines. Problem is, the underlying files change 2-3 times a day. What's a quick, efficient way to only rebuild the ZIP archive file on our Linux system if a file's changed, but leave it as-is if everything's stayed the same?

I'm trying to write a shell script that will accept a street address and output the latitude and longitude of that address, for geocache purposes. How can I do that?

I just bought a slick ASUS Eee PC netbook, model 1000HA, and want to configure it to work with both Microsoft Windows XP, which is already installed, and Ubuntu or some other flavor of Linux. How can I do that without having to reinstall WinXP?

I'm frustrated as heck! I clicked on a URL and next thing I knew I was on a completly different site that was quite, um, inappropriate for work. I know how to write a redirect in my own script, but I am wondering: how can I unwrap, decode, slow down or trace a sequence of redirects so I can see what's going on? If it helps, I have a Linux system I can use for the task.

I seem to recall a long time ago that when you installed Mac OS X you also got a bunch of cool Unix command line developer tools, including a C compiler, debugging tools and much more. I'm taking a C programming class at the local community college and would like to install these tools, but have no idea where they are any more. Help?

Please, gimme a advice how to correctly use loop "for i in `seq 1 10`" for Mac OS X, echo $SHELL->/bin/bash, because when I write simple strip: for i in `seq 1 10`;do echo $i;done it outputs -bash: seq: command not found.

On page 329 (Hour 16) of your book Teach Yourself Unix in 24 Hours is the example:

Are you able to quickly explain what the line test $value < $(echo $string | wc -c) is actually trying to do? I don’t quite understand the $(…) part … and is the < performing a ‘redirection for input’ or is it meant to be ‘less than’?

Amazon.com's jumped on the wagon, and Meebo has too: they automatically give you a different version of their site if you're browsing from an Apple iPhone. I want to do that too. How the heck do I detect that a visitor has an iPhone?

I have read about 15 chapters of your book (Teach Yourself UNIX in 24 Hours) so far. We are using vi. On the PS1 command, how do I see what is in it so I can add to it and not change what is already there? We are using bash. What I see now is: ctdaywbsdv:/u/gwilki$

When I enter ‘echo $PS1’ I get: $ \[\e[0m\]

How do I keep the above and add the histcmd option? What does the \e and 0m\ mean? What do the [] the square brackets mean? I can’t find a man page for PS1. How do I find the rest of the options for this PS1?

In which we get the hottest video game system from Christmas 2006 and turn it into a Linux box? You bet!

If you're still thinking about video game systems as being just a wee bit more technologically advanced than an old Coleco or Atari 800, you've got quite a surprise coming the first time you crack open the proverbial hood. While the new Nintendo Wii (pronounced "wee", oddly enough) has some slick hardware, as does the Microsoft Xbox 360 device, the real winner in the technology race is the rather amazing Sony Playstation 3 system.

Built around an IBM Cell Broadband Engine processor, the PS3 includes a high def Blu-ray drive, four USB 2.0 ports, an Nvidia graphics processor with 256MB of separate video RAM, support for Compact Flash, SD and Memory Stick devices, Ethernet, built-in 802.11b and g, Bluetooth, an HDMI port and support for all the video resolutions you can imagine, including 480i, 480p, 720p, 1080i and the holy grail, 1080p. Sounds like a computer, not a video game system, doesn't it?

I just finished Learning Unix for Mac OS X Tiger, and think it is an excellent little resource. I'm recently out of school, a school where we weren't taught anything about Unix, just enough to get by. I started work with the data converter team at Agilent labs, and have been able to glean quite a bit off of them (considering many of them were either directly or indirectly responsible for writing many of them commands in common use today). Thus, I'm often embarrassed to ask them questions about exactly some of the stuff you cover in the book.

Okay, now for the question: at work, they have the terminal set up such that the command line works like vi. That is, if I want to search my command history, I simply change mode via escape, type /pattern_to_be_searched, it finds the command, and then I can use other vi commands to change the command a little bit, and then execute it via the shell. How do I set this up in OS X?

I have a script that does an ftp from a SCO UNIX server to windows server to get files from the windows server. The script is set in the cron to run every xx minutes. Sometimes the script will hang and leave a process running. This can bog down the UNIX server. I want to be able to do two things. 1. I want to make sure that the script doesn't hang - so it should terminate after xx minutes (the files are very small that it is getting). And 2. I want the script to test to make sure that it is not already running, before starting again. THANKS

I've been looking at your script to count executable binaries in the book Wicked Cool Shell Scripts and I think that there's a problem in the script. Specifically, what happens if I have a directory in my PATH more than once?

Just picked up your book Wicked Cool Shell Scripts and already have one quick question: While working on the startup scripts, I would like to place log timers at certain portions of scripts. Is it possible to log point A at he beginning of a section, do the processing, log point B at the end of the section and then log B minus A so I know exactly how long a section took to process?

I've been running the Python-based "mailman" mailing list management program for quite a while with good results, but all of a sudden when I try to start it up I get the error "Site list is missing: mailman" and it won't start. What the heck? How do I fix this?