Next week I am getting an exam on using basic commands and shell scripting using terminal in Ubuntu. Please help me out with two quick questions:
-Does a practice environment for the Ubuntu terminal exist? I don't want to dual boot with Linux, so I want to find somewhere I could practice using some basic terminal commands as Cygwin seems to be quite different from the ubuntu terminal.
-What does the col command in Linux do? The manual page is here: Link, but I find that hard to understand, and since it doesn't work in Cygwin, it's hard to interpret! Also, why would one use man piped to col -b -x?
Thank you very much and sorry for the probably silly questions!
You can use the Ubuntu LiveCD boot (boots up an Ubuntu system without actually installing it) and experiment with the Ubuntu terminal shell. Its actually the same CD as the standard Ubuntu installtion CD... you just chose "Try Ubuntu" instead of "Install Ubuntu" once it boots up:
https://help.ubuntu.com/community/LiveCD
col is program to filter out reverse-linefeeds (i.e. the backspace character) from text input. In the olden days of line printers, a common method to achieve boldface print was to print a character, then print a backspace character, then print the character again. This would make the printer strike the character twice in the same place. Some programs would emit text files formatted in this way (man is one such program)-- but if you then tried to display that text file to your terminal screen, you might end up seeing something like this: "here is b^Hbo^Hol^Hld^Hd text".
col -b simply filters text input to strip out those extra backspace and double-strike characters. The -x option converts tab characters to space characters, which might be useful if the output was formatted for a device with a particular tab width, but then displayed on a different device.
man pages often have the backspace/double-strike text embedded in them, so man piped into col was often useful.
Nowadays, most terminal emulators actually know how to handle the backspace/double-strike, so col doesn't get used as much.
Far better (easier to use, install, maintain, etc.) than Cygwin, and perhaps less resource-using than a virtual machine, is http://andlinux.org . That will give you a shell on your Windows desktop, and you can play with the col command to better understand it.
Win-bash is essentially the same shell as linux, but on windows. You can use this to experiment outside Linux but I'm not sure how effective it is.
Other options are virtual machines, and if you don't mind a reboot, you can install ubuntu with wubi which means it can be deleted from windows' add/remove programs when you are done with it. (Or just use the live disc)
Col has very limited use for most people, it only affects programs that write lines asynchronously as opposed to line by line...
Related
I'm trying to make a bash script that behaves differently based on the terminal program that someone is using (Putty, mobaxterm, etc). Is there any way to retrieve this kind of information from a bash script?
I was searching around online but I was not able to find anything (or I'm just wording it incorrectly, which could be a distinct possibility).
thank you
You need to understand that these are terminal emulators. There is a simple, crude identification function for (most?) modern line terminals (now that's an oxymoron!) but it will return something like vt102 or xterm i.e. whatever the emulator is emulating; not the identity of the program performing this emulation. Incidentally, this is usually used when the session is initiated, and reflected in the value of the $TERM environment variable.
The common way to do this is the environment variable TERM. Try
echo $TERM
That should output the terminal emulator's type, indicating its capabilities. Often, though not always, the value of TERM will be the name of the terminal emulator. For example, xterm may set TERM to xterm, or to xterm-color, depending on configuration.
Note that the user can change this variable, so it may contain something completely different.
That said, if you want to do fancy things with the terminal from a script, you don't need to build support for different terminals by hand. There are various libraries that offer all the usual functions (clear terminal, resize window, change font etc.). The most popular one is terminfo; there are various packages that build on terminfo.
Is that possible to read text from clipboard on Linux udner X?
I select some text in a browser (Firefox for example) then click Edit->Copy.
Now I need this text in my application. I am using plain XLib. No GTK, no QT.
I do not want to use external apps like xsel. I studiet xsel source code, DAMN it is over 1000 lines. In Windows I am used to GetCLipboardTextW() one function call. That's all I need. Why is this so sophisticated? I have read this already:
http://www.sbin.org/doc/Xlib/chapt_12.html
And some more, I know there are many kinds of clipboards in X, selections, cut buffers etc. It does not help! Give me some code that compiles and works. No external libraries please no sudo apt-get install something, no "Are you using KDE(GNOME/whatever)?".
xclip is just 600 lines of code, but much of it seems to be due to processing command line options, reading input files, etc. Looking at main and doOut the core of what it does seems to be:
XOpenDisplay(...)
XCreateSimpleWindow(...)
XSelectInput(...)
XFetchBuffer(...) or xcout(...)
XCloseDisplay(...)
I have laptop-desktop setup at home and I have successfully cloned my Archlinux installation from one to another. However, I would like to avoid having to {install all new software, edit settings, update} twice, so I was wondering if it'd be possible to log over ssh from laptop to desktop, do something in terminal and have linux copy everything I type into second terminal with ssh logged in?
Thanks for ideas!
You could type the commands into one terminal then edit ~/.bash_history and save the commands into a script. Copy the script onto the machine with the second terminal and execute it. The advantage of this is now you have a script that saved your setup so you can reuse it whenever you need to.
You can use clusterssh, which duplicates your typed input across multiple systems. It is designed for situations in which the exact same tasks, such as software installation or configuration commands, are needed to be performed exactly the same on multiple systems. See http://sourceforge.net/projects/clusterssh/. Also, the KDE Konsole terminal has similar functionality.
Warning: you know how they say "there's not such thing as a stupid question"? Well, this one is, or, I suspect it's really minor, but wth, why not ask. Search engines didn't bring me anything remotely useful, though that could be bad searchterm-fu.
I recently downloaded sqlite3 onto Ubuntu 10 to start learning SQL commands. I un-tar'd 3.7.12.01 and make installed.
After creating a test.db with create table test (id) I decided to see what I'd get if I cat it. Just because.
The result is an EOT character (u+0004) which is sitting right over my prompt. Illustrated screenshot: http://imgur.com/omfMa
I realise this is not the type of file you would use cat on. I only want to know, before I go further,
does the strange placement of this character signal any future issues when actually playing around with SQL, or some issue with newlines, or fonts (this is monofur set at a high font size) or similar?
I've never seen a result character placed directly over my prompt before.
The character is placed over your prompt, because it is a double-width character, and terminals in general are not good at handling double-width characters. It does not mean anything.
There are some control codes which can do very funny things with your terminal, such as changing colors, fonts etc.
But none of them do really harm - you should be able to reset your terminal to a healthy state, or close it and open a new one.
I am writing a script on Red Hat Linux (I forget the version) that needs a header, but the banner command is not there for me to use and I won't be able to get it installed. I read via Google that it may well have been deprecated.
So is there a new version of the command that produces similar results, or a way I can replicate the command, or even just temporarily change the script output so that characters are a different size?
I've tried looking at stty but we don't access via xterm, we log in directly via putty.
In its simplest form, 'banner' is less than a few pages of code (e.g. this one). Perhaps you could just compile and run it from your home directory?
Use some web site, for example http://patorjk.com/software/taag/.
If you need it frequently you can create a script to scrap the result.
BTW, stty has nothing to do with your problem, I don't know why you mentioned it.