Hello all Linux users. I am new to the linux world and am having an issue with an exam. I wanted to see if I could possibly get some assistance. All of these questions are in relations to CentOS.

1. You have a big file called "friends", and want to find all the lines that do NOT have the word "california" in it, and you want to sort them alphabetically, and save that in a file called "newb". How would you do that in one line of commands?

2. You want the permissions on a file to look like -rwxr-x--- for the file "newb"
And you want the group set to "newguy" and the owner set to "root". Please use 2-3 commands to complete these tasks

3. How would you back up the directories /home/newguy/etc and /usr/local/lib to a file called important.tar ?

4. What does the rsync command do and please sync the directory ~/mystuff with ~/Desktop/backupofmystuff.

Also to whoever helps me out, I very much so appreciate you taking the time to reply. The due date for this exam is nearing and I've nearing 7 hours trying to finish the exam and these are the only questions I have not been able to figure out. Thanks

The above quote is taken from the LQ Rules section. So tell us what you have done to answer these questions and what your problems are in doing so.
jdk

Sorry, I should've read the rules and specified that they're not written verbatim. I reworded them and changed around the directories. As for the questions I have tried to figure them out I just have not been able to. For example for number 1, I have not been able to figure out how to put to command together, I know that for the grep -v command will search exclude a single word, the sort command will filter alphabetically and using > will print the output elsewhere, I just can't see to be able to come up with the proper command.

For number two I know chmod will change the group (or at least I believe it will chown will change the owner but I do not quite understand how to set the permissions like requested.

For the third one I know you can use the tar command, so I could do tar -vc important.tar (I believe this is correct but this is where I get stuck because I do not know how to back up two directories at once and send them to the same place)

For the last one, other than know that rsync is just used for copying, I'm not even sure at all how you would formulate that command. I've been at this for hours trying to figure these out (an of course the rest of the test) but I'm sincerely stuck.

OK, you have at least thought about it, so let's give a little nudge in the right direction...

The thing that you are looking for is called a "pipe", looks like this |, it is used to pipe the output of one command into another.

So using what you already know, try something like this...

You might need to add a case sensitivity flag in there, and there are a few sort options to look at, but note how the pipe is used - this is a cornerstone of Unix power.

See man grep and man sort for more.

This always seems obscure to new users, and is so much taken for granted by long time users that it seems difficult to give a quick explanation.

So first let's ask if you know whow to read those permissions -rwxr-x---? That is pretty fundamental to understanding how to set them. If not read your study material for "file permissions" and see the chmod man page as well.

Hint: It is a simple binary representation of three octal values in bit order r (read), w (write) and x (execute), and group order user, group and others. A letter in a given position means that it is enabled, a '-' means it is disabled.

So rwxr-x--- means the user (owner) has read, write and execute permission, the group has read and execute, others have no rights: "rwx" "r-x" "---".

Again, see the chmod man page and come back if you need help over the hump - at least then we will be speaking the same language.

You already seem to know what is needed. See man tar and try it out. (I hope that you have a system to try it on...)

See man rsync - think 'source' and 'destination'. Admittedly rsync has quite a few options, but just look at -a, -l and -v for now, pretty good hint.

Good luck and welcome to LQ!

1 members found this post helpful.

Thanks a lot for the help astro, I really do appreciate you taking the time to reply and help me out. I was actually able to figure out the first three questions with your assistance, I'm just trying to figure out the rsync command question. My brains about to explode from spending 10 hours trying to read though and learn these commands by myself. Unfortunately I have a teacher who doesn't exactly, "Explain" commands, rather just spits them all out and expects us to learn ourselves. I'll try to revisit this when I get a chance tomorrow and see if I'm able to figure it out, I've got till tomorrow night as 12 to finish my exam so I have a little bit of time - I also have class so I may be able to get assistance from my professor. Have a good night guys and thanks again for the help

You are welcome!

Glad to hear that you got the first three figured out - the rsync is easy too.

Good luck on the test!

If you're having trouble with rsync then this link may help you out. Give a shout if something isn't clear.
jdk

Hi,

Welcome to LQ!
Glad to see some initiative. Your instructor would be the first place to get detailed help.

I like to give new users these links;Along with your text for the class the above links will help you to learn. Sure a lot of information but each reference material above will enhance your abilities.
Hope this helps.
Have fun & enjoy!