Frequently Asked Questions - Unix-Linux | Computer Science and Engineering

Connecting to cse.unl.edu and other unix servers with ssh from Linux

Open a Terminal window. The instructions that follow are for Ubuntu Linux. Other distributions are similar.

Click on the grid button in the lower left corner.

ubuntu search icon

Enter "Terminal" in the search dialog that appears.

ubuntu terminal command search window view

In the window that appears when you click on the Terminal icon shown above, enter "ssh -Y username@cse.unl.edu". Substitue your cse user name for "username" in this command. You can omit the "-Y" flag if you do not want to use ssh X forwarding (and if you don't know what this is, you can safely omit it). The examples below use a user name of "sac".

ubuntu terminal secure shell connection initial system connection prompt

The first time that you connect to cse.unl.edu, or any other Linux/Unix server, a dialog like that shown above will appear. Answer "yes" to this.

Then enter your cse password.

ubuntu terminal window showing successful secure shell connection to remote host

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How to reset your MySQL password on cse.unl.edu

Resetting MySQL Password

If you have forgotten your MySQL password, To reset the MySQL password go to https://cse.unl.edu/account. Log in using your cse credentials and click the 'Reset MySQL Password' link. A new randomly generated password will be sent to you via email.

Changing MySQL Password from the MySQL CLI

If you know your old MySQL password, the password can be changed from MySQL workbench or from the MySQL command line interface (CLI). To chance your password from the CLI, connect to cse.unl.edu, run the mysql client, once connected, type 'set password=password('####');' and hit enter. Where '####' denotes the password you wish

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Connecting to the Windows Terminal Server from Linux

The instructions that follow are for Ubuntu Linux. Other Linux distributions are similar except for installing the "Remmina" program.

Click on the grid icon at the lower left of the screen.

ubuntu search icon

In the search dialog that appears enter "rdp". The Remmina application should appear in the results. Click on that icon.

ubuntu search window for Remmina application

In order to connect to our terminal server you need to add a customized connection. Click on the green "+" symbol in the Remmina program and enter the following information:

Profile name: csnt-ts (or another name that you'd like to use).

Server: csnt-ts.unl.edu

User password: your cse password

Domain: cs.unl.edu

Color depth: True color (24 bpp)

And then click the "Save" or "Save as Default" button.

Remote desktop settings window of Remmina application

Double click on the session you just saved.

Remmina session view

A dialog may appear asking you to accept a certificate for csnt-ts. You should accept the certificate.

Remmina certificate acceptance window

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Accessing cse.unl.edu using NoMachine - remote X11 GUI access.

NoMachine is a fast, multi protocol remote access client. Which allows RDP and X11 type connections to a variety of servers. We have a NX server installed on cse.unl.edu, which will allow GUI X11 access to cse.unl.edu. Below are steps on setting up a noMachine connection to cse.unl.edu

You can download and installed noMachine from https://www.nomachine.com/

To configure a new connection, after you launch noMachine:

from the Recent connections pane, click on ‘New’
for Protocol select NX
In the Host input enter ‘cse.unl.edu’
for Authentication method select Password
select the Don’t use proxy radio button.
Name your connection and finally click on Done

Once you have configured a connection to establish a connection:

from the Recent connections pane, double click on the named connection
Enter your cse.unl.edu username and password
Double click on the Create a new virtual desktop icon
Click thru the next four dialogs that provide you an overview on using noMachine

Tip: You can save your password, the connection type, and click on Don’t show this message again on the dialogs for one-click connection to cse.unl.edu

Note: Please log off when you are done working on cse.unl.edu. Simply disconnecting the NoMachine client will consume resources on the server and your session will be forcefully quit at somepoint, possibly resulting in loss of any unsaved data or settings.

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Linux SMB Printing

Note: Printing only works when you are on a Nebraska network.

Open System Settings
Open Printers:
Click on Add:
Expand Network Printer and select "Windows Printer via SAMBA":
Enter csnt and the name of the printer that you want to add such as "Avery-ps15" and select "Set authentication details now" and enter cs.unl.edu\username (where username is your cse user name), enter your cse password in the Password: field and click Forward:
Select Generic (recommended) and click Forward on the next window:
Select PostScript in the Models column of the next window and select Generic PostScript Printer Foomatic/Postscript [en] (Recommended) column:
Enter a short name for the printer, such as "ps15", and a "Human-readable" name for the printer such as "Avery-ps15" and then click Apply. The short name can be used later for command-line printing and the "Human-readable" name will show up in print applications that use the system's GUI.
You can click Cancel on the popup window or click Print Test Page. The test page will be deducted from your print quota if you choose to print it.

Linux Mint uses very much the same procedure except instead of being called "System Settings" the system configuration application is called "Control Center". Other Linux distributions are similar.

If you want to take advantage of more advanced printer features, such as duplexing or stapling, you can use a printer-specific driver for the printer models as seen at the bottom of Printing from Mac via SMB 10.8+ section of this FAQ

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How to Format Your Thesis Using LaTeX

The Office of Graduate Studies dictates the style and format for a thesis at the University of Nebraska-Lincoln. Information about these standards can be found on their website for current students at http://www.unl.edu/gradstudies/current/, and specifically in a publication titled "Guidebook For Preparation and Submission of a Thesis".

The Department of Mathematics maintains a LaTex class file that helps format your thesis to Nebraska's guidelines. This template may be helpful to Computer Science and Engineering students as well. Look for the "NU Thesis LaTeX Class File" under the Resources section of this page: http://www.math.unl.edu/graduate/

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Compilers and Interpreters available on cse.unl.edu

Compilers

gcc GNU CcCompiler

g++ GNU C++ compiler

javac Java compiler

gfortran GNU Fortran compiler

clisp Common Lisp

alisp Allegro Common Lisp

Interpreters

perl Perl command line scripting language

php Command line and web scripting language

ruby Command line and web scripting language

pyton Command line scripting language

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A simple unix text editor - pico

To use pico, type "pico filename" where filename is the file you with to create or edit. Once in pico, you will see a list of pico commands you can use, shown on the bottom of the screen. The '^' symbols means <CTRL>. To view the pico help screen the command shown on the bottom of the screen is "^G" which means <CTRL>-G.

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Basic Unix Commands

Note on systax used in document:: items in [] are optional; items in {} can be repeated 0 or more times.; fn = filename (possible with wildcards); dir = directory name

File System:

cat fn {fn}: concatenate, can be used to display a file.
more fn {fn}: displays file(s) one screenful, at a time. At MORE prompt enter: space bar - for next screenful <cr> - for next line, q - to quit more command.
cp fn1 fn2: copy file - fn1 to fn2, fn1 remains.
mv fn1 fn2: move (rename) file - fn1 to fn2, fn1 no longer exists.
rm fn: remove (delete) file.
lpr -Pprinter_name fn: print a file, printer_name = ps16 or ps17.
ls [fn]: list files in current directory option filename is usually used to display files matching wildcards. (ie. ls *.s will list all assembly language source files.)
ls -lgRa: Recursive listing of all files within all subdirectories. Longest, most descriptive format.
cd [dir]: change working directory, ``home directory" if not specified. cd .. will backup one level in the directory structure.
pwd: print working directory path.
mkdir dir: make a new directory, giving it the name dir (within the current directory)
rmdir dir: remove (delete) the directory named dir (the directory must be empty)
file fn: Tries to determine what kind of information is in a file by consulting the file system index and by reading the file itself.
du: Prints a summary of total space occupied by all files in a hierarchy.
sort fn: Sorts ASCII files line-by-line.
chmod: Change file permissions. See the man pages for a complete description of settings. Use this command to determine whether files can be readable by other people.
find . -name filename: In it's most simple form find will display all files in this and any subdirectories which name matches filename. See the man page for find for a complete description of this command. Find can be use to find files matching name patters, dates, owners, sizes, etc. and to perform action on matched files.
gzip fn: Use this to compress files not needed immediately to conserve disk space. A ``.gz" will be appended to the filename.
gzip -d: Uncompresses files with ``.Z" at end of filename.
head {-n} fn: Prints first n lines of a text file. If no number is specified, the default is 10.
tail {-n} fn: Prints last n lines of a text file. If no number is specified, the default is 10.
tail {-n} fn: Prints last n lines of a text file. If no number is specified, the default is 10.
grep string fn: Print occurrences of string in file

Remote Connection:

ssh remote_host: Launch a secure shell to the remote host specified.

Communication:

finger: list users currently on the system.
who: list users currently on the system.
w: what, similar to who but includes what they are doing.
pine: Email message utility.
pine username: will send Email to username.
talk username: allows two users to have an interactive conversation over the computer.
write username: allows a user to put a message on another users screen.
mesg n: Makes it so other users cannot interrupt you with talk requests, and write messages.

Help:

man command: manual, returns the manual for the given command from the UNIX on-line manual. If you cannot find a man page for a command, there may be one in a directory that isn't in your MANPATH. Your MANPATH is setup in the .login file and a command's man page is usually in a man directory off the same parent directory as the command. For example, if the command is located in /usr/local/bin, its man page is probably in /usr/local/man.
man -k keyword: display manual headings containing the word keyword.

Miscellaneous:

alias name def: Assigns ``def'' to the alias ``name''. Usually found in the .cshrc file. For example ``alias dir ls -la''.
clear: Clears screen.
history: List history of commands used.
!!: re-execute the last command entered.
!x: re-execute the last command that started with the given letter, eg !c will re-execute the last command that began with the letter c.
jobs -l: list all currently stopped or background jobs with job numbers and process ID's.
kill [-signal] %jobnumber: kill the given job number. Use the "jobs" command to show running jobs. You might need to kill a job to logout if you have accidentally put a job into the background or stopped a job. Use -TERM or -KILL singlas to force quite jobs.

kill PID: kill the given Process. refer the "ps" command to find running processes. Use -TERM or -KILL singlas to force quite jobs.
ps -fa: list all your current processes. See the man page for a full description.
<control>C: kill the current process - the one in the foreground
<control>Z: suspend foreground process.
bg: put a suspended job in the background.
fg: put a suspended or background job in the foreground.
date: display time and date.

To find out about more commands, click here.

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Editing a File on Unix with vi - Basic Commands.

What is `vi`?

The default editor that comes with the UNIX operating system is called vi ( visual editor). [Alternate editors for UNIX environments include pico and emacs, a product of GNU.]

The UNIX vi editor is a full screen editor and has two modes of operation:

Command mode commands which cause action to be taken on the file, and
Insert mode in which entered text is inserted into the file.

In the command mode, every character typed is a command that does something to the text file being edited; a character typed in the command mode may even cause the vi editor to enter the insert mode. In the insert mode, every character typed is added to the text in the file; pressing the <Esc> ( Escape) key turns off the Insert mode.

While there are a number of vi commands, just a handful of these is usually sufficient for beginning vi users. To assist such users, this Web page contains a sampling of basic vi commands. The most basic and useful commands are marked with an asterisk ( * or star) in the tables below. With practice, these commands should become automatic.

NOTE: Both UNIX and vi are case-sensitive. Be sure not to use a capital letter in place of a lowercase letter; the results will not be what you expect.

To Get Into and Out Of `vi`

To Start `vi`

To use vi on a file, type in vi filename. If the file named filename exists, then the first page (or screen) of the file will be displayed; if the file does not exist, then an empty file and screen are created into which you may enter text.

*	`vi filename`	edit `filename` starting at line 1
	`vi -r filename`	recover `filename` that was being edited when system crashed

To Exit `vi`

Usually the new or modified file is saved when you leave vi. However, it is also possible to quit vi without saving the file.

Note: The cursor moves to bottom of screen whenever a colon ( :) is typed. This type of command is completed by hitting the <Return> (or <Enter>) key.

Basic Command	Command	Description
here	`:x` `<Return>`	quit `vi`, writing out modified file to file named in original invocation
	`:wq` `<Return>`	quit `vi`, writing out modified file to file named in original invocation
	`:q` `<Return>`	quit (or exit) `vi`
*	`:q!` `<Return>`	quit `vi` even though latest changes have not been saved for this `vi` call

Moving the Cursor

Unlike many of the PC and MacIntosh editors, the mouse does not move the cursor within the vi editor screen (or window). You must use the the key commands listed below. On some UNIX platforms, the arrow keys may be used as well; however, since vi was designed with the Qwerty keyboard (containing no arrow keys) in mind, the arrow keys sometimes produce strange effects in vi and should be avoided.

If you go back and forth between a PC environment and a UNIX environment, you may find that this dissimilarity in methods for cursor movement is the most frustrating difference between the two.

In the table below, the symbol ^ before a letter means that the <Ctrl> key should be held down while the letter key is pressed.

Basic Command	Command	Description
*	`j` or `<Return>` [ or down-arrow]	move cursor down one line
*	`k` [ or up-arrow]	move cursor up one line
*	`h` or `<Backspace>` [ or left-arrow]	move cursor left one character
*	`l` or `<Space>` [ or right-arrow]	move cursor right one character
*	`0` (zero)	move cursor to start of current line (the one with the cursor)
*	`$`	move cursor to end of current line
	`w`	move cursor to beginning of next word
	`b`	move cursor back to beginning of preceding word
	`:0` `<Return> or 1G`	move cursor to first line in file
	`:n` `<Return> or nG`	move cursor to line `n`
	`:$` `<Return> or G`	move cursor to last line in file

Screen Manipulation

The following commands allow the vi editor screen (or window) to move up or down several lines and to be refreshed.

Basic Command	Command	Description
	`^f`	move forward one screen
	`^b`	move backward one screen
	`^d`	move down (forward) one half screen
	`^u`	move up (back) one half screen
	`^l`	redraws the screen
	`^r`	redraws the screen, removing deleted lines

Adding, Changing, and Deleting Text

Unlike PC editors, you cannot replace or delete text by highlighting it with the mouse. Instead use the commands in the following tables.

Perhaps the most important command is the one that allows you to back up and undo your last action. Unfortunately, this command acts like a toggle, undoing and redoing your most recent action. You cannot go back more than one step.

* u UNDO WHATEVER YOU JUST DID; a simple toggle

The main purpose of an editor is to create, add, or modify text for a file.

Inserting or Adding Text

The following commands allow you to insert and add text. Each of these commands puts the vi editor into insert mode; thus, the <Esc> key must be pressed to terminate the entry of text and to put the vi editor back into command mode.

Basic Command	Command	Description
*	`i`	insert text before cursor, until `<Esc>` hit
	`I`	insert text at beginning of current line, until `<Esc>` hit
*	`a`	append text after cursor, until `<Esc>` hit
	`A`	append text to end of current line, until `<Esc>` hit
*	`o`	open and put text in a new line below current line, until `<Esc>` hit
*	`O`	open and put text in a new line above current line, until `<Esc>` hit

Changing Text

The following commands allow you to modify text.

Basic Command	Command	Description
*	`r`	replace single character under cursor (no `<Esc>` needed)
	`R`	replace characters, starting with current cursor position, until `<Esc>` hit
	`cw`	change the current word with new text, starting with the character under cursor, until `<Esc>` hit
	`cNw`	change `N` words beginning with character under cursor, until `<Esc>` hit; e.g., `c5w` changes 5 words
	`C`	change (replace) the characters in the current line, until `<Esc>` hit
	`cc`	change (replace) the entire current line, stopping when `<Esc>` is hit
	`Ncc` or `cNc`	change (replace) the next N lines, starting with the current line, stopping when `<Esc>` is hit

Deleting Text

The following commands allow you to delete text.

Basic Command	Command	Description
*	`x`	delete single character under cursor
	`Nx`	delete N characters, starting with character under cursor
	`dw`	delete the single word beginning with character under cursor
	`dNw`	delete `N` words beginning with character under cursor; e.g., `d5w` deletes 5 words
	`D`	delete the remainder of the line, starting with current cursor position
*	`dd`	delete entire current line
	`Ndd` or `dNd`	delete `N` lines, beginning with the current line; e.g., `5dd` deletes 5 lines

Cutting and Pasting Text

The following commands allow you to copy and paste text.

Basic Command	Command	Description
	`yy`	copy (yank, cut) the current line into the buffer
	`Nyy` or `yNy`	copy (yank, cut) the next N lines, including the current line, into the buffer
	`p`	put (paste) the line(s) in the buffer into the text after the current line

Other Commands

Searching Text

A common occurrence in text editing is to replace one word or phase by another. To locate instances of particular sets of characters (or strings), use the following commands.

Basic Command	Command	Description
	`/string`	search forward for occurrence of `string` in text
	`?string`	search backward for occurrence of `string` in text
	`n`	move to next occurrence of search string
	`N`	move to next occurrence of search string in opposite direction

Determining Line Numbers

Being able to determine the line number of the current line or the total number of lines in the file being edited is sometimes useful.

Basic Command	Command	Description
	`:.=`	returns line number of current line at bottom of screen
	`:=`	returns the total number of lines at bottom of screen
	`^g`	provides the current line number, along with the total number of lines, In the file at the bottom of the screen

Saving and Reading Files

These commands permit you to input and output files other than the named file with which you are currently working.

Basic Command	Command	Description
	`:r filename` `<Return>`	read file named `filename` and insert after current line (the line with cursor)
	`:w` `<Return>`	write current contents to file named in original `vi` call
	`:w newfile` `<Return>`	write current contents to a new file named `newfile`
	`:12,35w smallfile` `<Return>`	write the contents of the lines numbered 12 through 35 to a new file named `smallfile`
	`:w! prevfile` `<Return>`	write current contents over a pre-existing file named `prevfile`

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MySQL Database Account - Requesting & Connecting

MySQL is the general purpose database available for student use. Each user is allowed one database. This database is automatically created after requested by a user and is named the same as your cse username. Users can create as many tables as they want but we ask that they keep all databases to a reasonable size.

Requesting a MySQL Account and Database
Any user with a CSE account can request access to the MySQL server running on cse.unl.edu. To do so, log in to the CSE Account Management Utility (AMU) page at cse.unl.edu/account with your CSE account credentials. Once you log in, click the Account Settings link on the left page. From there, check the box for MySQL Account and then click Save. You should then receive an email message with your MySQL account credentials.

Connecting to MySQL Database
To connect to a MySQL database from the command-line on cse.unl.edu, type 'mysql -p' and hit enter. The password you will be prompted for will be your MySQL password, which is different from your CSE password.

To connect to a MySQL database from the command-line from another computer with the mysql command line client installed. Run 'mysql -h cse.unl.edu -u YOUR_CSE_LOGIN -p' and hit enter. Note: the password you will be prompted for will be your MySQL password, which is different from your CSE password.

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gcc	GNU CcCompiler
g++	GNU C++ compiler
javac	Java compiler
gfortran	GNU Fortran compiler
clisp	Common Lisp
alisp	Allegro Common Lisp

perl	Perl command line scripting language
php	Command line and web scripting language
ruby	Command line and web scripting language
pyton	Command line scripting language

Connecting to cse.unl.edu and other unix servers with ssh from Linux

How to reset your MySQL password on cse.unl.edu

Connecting to the Windows Terminal Server from Linux

Accessing cse.unl.edu using NoMachine - remote X11 GUI access.

Linux SMB Printing

How to Format Your Thesis Using LaTeX

Compilers and Interpreters available on cse.unl.edu

Compilers

Interpreters

A simple unix text editor - pico

Basic Unix Commands

File System:

Remote Connection:

Communication:

Help:

Miscellaneous:

Editing a File on Unix with vi - Basic Commands.

What is vi?

To Get Into and Out Of vi

To Start vi

To Exit vi

Moving the Cursor

Screen Manipulation

Adding, Changing, and Deleting Text

Inserting or Adding Text

Changing Text

Deleting Text

Cutting and Pasting Text

Other Commands

Searching Text

Determining Line Numbers

Saving and Reading Files

MySQL Database Account - Requesting & Connecting

What is `vi`?

To Get Into and Out Of `vi`

To Start `vi`

To Exit `vi`