Introduction

All examples used in this document will be from the rci login machines. User input will appear in this typeface.Text that is in italics represents place holders for specifics that you would supply. The notation <CTRL>d means that you should hold down the control key while typing the indicated character (in this case d).

In order to access a Unix computer, you must have a valid account. If you are an employee or a registered student you may create an account for yourself. For instructions in how to do this see the NBCS document Creating Accounts on OIT Systems. Do not give your password to other people; the only one who should have access to an account is the single user who it was assigned to and as such the owner is held responsible for the activity on their account.

Command Format/Execution

command-name [options] [parameters]

A command-name is usually an abbreviation of the name of the command. For example ls will list a directory's contents, mv will move or rename a file, and cp will copy files.

An option is a single letter or number preceded by a space and a hyphen '-': ls -l. Options may be grouped together with a single hyphen or separated with a space and a hyphen for each, ls -la is the same as ls -l -a (see the command descriptions at the end of this document for a brief explanation of this command). The square brackets are used here (and in Unix manuals) to indicate that the enclosed items are optional and may be left out of the command.

Parameters are usually file names (may include a path, which is explained later) or expressions.

To execute a Unix command simply type in the command-name and all options and parameters required to achieve the effect desired. After a command has been entered, the computer will simple issue another prompt, unless there has been a problem in its execution or the execution of the command requires some interaction.

Command Format/Execution Editing Commands

Getting Online Help: Man pages

In order to use the man command, there are some things you should know. First, many of the man pages were written by technical people for technical people and assume the person reading them knows more about Unix than a novice will. Second, the program used to display the man pages is called more (see the command descriptions at the end of this document for a brief explanation of this command). Third, for substantial programs, the manual pages do not give every detail you may need. They should tell you how to run the item selected but be short enough to read on your terminal. So man pc will tell you how to run the Pascal compiler and list all of the options, but it will not be a Pascal language reference manual. There are separate manuals for programming languages, the mail system, the document processors, and certain other complex pieces of software.

Generally the man page will refer to this documentation if it exists. Fourth, the man pages are organized into chapters. For example, if you use the command man -k unlink (man -k is described later in this section) to find out what documentation is available on unlink, it will offer man pages from chapters 2 and 3. It is useful to know that chapter 2 is on system calls and chapter 3 is on subroutines. So if you were looking for the Fortran subroutine information, you would look in chapter 3. The topics for each chapter are:

Chapter Topic

1. Commands
2. System Calls
3. Subroutines
4. Special Files
5. File formats and conventions
6. Games
7. Macro packages and conventions
8. Items of interest to system managers

3F Fortran library

3M Math library

3N Internet Network library

3S C standard I/O routines

3X Other libraries

The man command is useful when you know what something is called. But if you can't remember the name of a command, the man command can't help because you can't tell it what to look up. The man option -k causes man to list the title lines of the man pages that have the supplied keyword in it. So man -k remove would show all the title lines that contain the word "remove". Generally the title lines contain most of the keywords people would use for looking them up. Using combinations of "man -k" and "man", you should be able to find most of what you want to know about Unix.

Files

Editors

When you are in an editor, you are actually working on a copy of the file, not the permanent file. Changes are made to the copy that the editor is maintaining in memory. When you are finished, instruct the editor to save the current working copy as the new permanent copy (or into a new file altogether). This means that if you exit the editor without saving the changes, the changes will be lost (sometimes you may want this to happen).

Though most users choose Emacs as their editor, there are other editors. One advantage of Emacs is that it is available on most systems (Unix or otherwise) here at Rutgers. Although different machines may have different versions of Emacs, the differences between versions are slight.

The best introduction to Emacs is the emacs tutorial program: teach-emacs. To begin the tutorial, use the command teach-emacs or, from within emacs, type <CTRL>h t.

To edit a file with Emacs, type Emacs filename , whether the file exists or not. If the file does not exist, it will be created the first time you issue a save command.

If the computer does not know what kind of terminal you are using you will get the error message:

emacs: terminal XXX isn't powerful enough to run Emacs

Contact the OIT/NBCS Help Desk at (732) 445-HELP for help in determining your terminal type.

Printing Files

into your .login file (using the emacs text editor) and then logout and back in. To see what printers are available type the command printers. Some printers require a specified bin (so you will know where to find your ouput) a bin for the above printer is specified by setenv BIN H07E

With the above two settings lpr filename will send the specified file to the printer nbhilliop2 with a bin specification of H07E. To specify other printers or bins use the -P and -B options to the lpr command, as in lpr -Ptillettp1 -Bt075 filename which will print to the tillettp1 printer and get binned in T075.

Directories and Paths

There are many different directories on a disk. A user can have a home directory that contains a directory (known as a subdirectory). For example, John Q. Smith can have a main directory 'jqsmith', and a subdirectory 'work'. The subdirectory 'work' is contained within 'jqsmith'; 'work' could also be referred to as a child directory of 'jqsmith'.

This, in turn, falls within the structure of the entire Unix file system, which can be thought of as an upside down tree (as in a family tree). The top directory is called root, and is noted as "/". Next come other directory names, such as usr, u1, u2, etc. On Rutgers's systems the user directories are subdirectories of u1, u2, or some other u#. As shown below, the directory jqsmith is a subdirectory of u2, which in turn is a subdirectory of the root directory. On larger Rutgers systems, the u# directories are placed under a directory named for the system (eden or rci).
 

/ usr etc u1 u2 
           |
        jqsmith 
           |
          work

The directory you are in can be indicated by a '.' (period). The directory immediately above a directory is called its 'parent' (u2 is the parent of jqsmith). The parent of the current directory can be indicated by '..' (two periods). If the current directory is jqsmith, you can refer to a file in the parent directory with ../filename or by /u2/filename. If you are in /u2/jqsmith, a file in the subdirectory work may be referenced with ./work/filename or by /u2/jqsmith/work/filename. The '.' and '..' notations are 'relative pathnames' because the reference is relative to the current directory.

A short cut to denote a user's home directory is to precede the username with a '~' (tilde). The home directory of J. Q. Smith may be referred to as ~jqsmith. This is useful when copying from the current directory to your home directory, as in: cp filename ~/. which will copy the file named 'filename' from the current directory into your home directory ('~/ ' = current user's home directory, '.' = reuse the original filename).

Three of the many directory related commands are ls, pwd, and cd. The command ls lists the contents of a directory. The command pwd will print the working (current ) directory name to the screen. The command cd allows you to change directories.

Programming Languages

Two program debuggers that are commonly available are dbx and adb. For more information see the man pages. For C code there is also a pre-compilation program checker called lint.

Mail

Unix has mail facilities, so you can leave messages for other users and read those sent to you. The supported mail package is Pine. To get information on Pine, CLICK HERE for details.

News

Most Unix systems have a news posting/reading feature often referred to as NetNews. This is a facility for sharing information between users on many systems around the world. The information is broken up into various topics (called newsgroups), such as IBM microcomputers, cooking, astrology, music, etc., which are updated on a continuous basis. This provides an almost interactive conference in each group. The supported program for reading news is nn. There are a number of NBCS documents on nn available. CLICK HERE for details.

Input/Output Redirection

Unix works on the assumption that there is always a place for output, input, and error messages. Most of the time input is taken from the keyboard and output and errors are displayed on the screen. These are commonly referred to as the standard input, output, and error. One of the nice features of Unix is that you can change where these are. Sometimes it is desirable to have your input come from a file, and have your output go to a file. This is possible using redirection. The standard input and standard output of a command may be redirected by adding one or more of the following to the end of a command:

< filename	Use the file filename as the standard input.
> filename	Use the file filename as the standard output. If it does  not exist, then it is created; if it exists, its previous contents are lost.
>> filename	Use the file filenameas the standard output like > but  appends the output to the end of filename.
> & filename	Use the file filename as the standard output and standard error. Replace contents of filename with new information.

 

 To redirect the contents of a file to be the input for a command , type

command < filename

To mail a file to jqsmith@rci.rutgers.edu the command

mail jqsmith@rci.rutgers.edu < filename

would do the job in one command.

To redirect the output of a command to a file you would type

command > file

For example, the cat command usually takes one or more files and displays them on the screen, as in: cat file1 file2. By using redirection, it possible to append file2 to the end of file1 and place the results in file3. This is done with:

cat file1 file2 > file3

which will replace any prior contents of file3 with first the contents of file1 followed by the contents of file2.

Now suppose you want to append the contents of file4 and file5 to the end of file3. This is done with

cat file4 file5 >> file3

In this case the original contents of file3 are kept and the content of other files are added to the end of file3.

When using > and >> any error messages that occur will still be sent to the terminal screen. To redirect error messages in addition to output use >& or >>&. For instance you do an ls of a directory and see

Calendar/
Docs/
F-prot
F772F90*
F90/
FAQ.eden

As a final illustration of redirection, assume the executable program test takes its input from the keyboard (standard input) and sends output to the screen (standard output). To run a data file through the program, have the output go to an output file, and to have error messages go to a separate error file, use the command

(./test < datafile > outfile) >& errfile

The parentheses group what is inside them as a separate action then the output of that (only error messages in this case) will be redirected to errfile.

For example, the cat command usually takes one or more files and displays them on the screen, as in: cat file1 file2. By using redirection, it possible to append file2 to the end of file1 and place the results in file3. This is done with: cat file1 file2 > file3 which will replace the prior contents of file3 with the contents of the other files. Now suppose you want to append file4 and file5 to the end of file3. This is done with cat file4 file5 >> file3. In this case the original contents of file3 are kept and the other files are added.

To further illustrate the concept of redirection, assume the executable program test takes its input from the keyboard (standard input) and sends output to the screen (standard output). To run a data file through the program, have the output go to a file, and to have error messages go to a separate file, use the command

(./test < datafile > outfile) >& errfile.

Pipes are another way to redirect output. A sequence of simple commands separated by '|' characters forms a pipe. The output of each command in a pipeline is used as the input for the next. For example, the pipe who | sort | lpr will work as follows: the who program will produce as output the names of currently logged in users. This output will then be the input to sort, which will put that list of users in alphabetical order. lpr will take this output and send it to the default printer.

Online Documentation

more /usr/local/doc/subdir/docname

(more is a command that allows you to view files one screenful at a time, see man more). To print a document found type

lpr -Plp16 -BH07D /usr/local/doc/subdir/docname

(meaning: lpr, print; -Plp16, to the printer lp16 in the Hill I/O area; -BH07D, the output will be placed into Hill Center bin 07 D, the file to print is /usr/local/doc/subdir/docname). In the examples above, "subdir" and "docname" should be replaced with the desired directory and document names. The command printers will display a list of printers available to the computer you are on.
 
 

Introductory Commands Online Help
man	display reference manual pages	man mantitle
man -k	the -k option locates commands by keyword lookup	man -k keyword
Commnicating With Other Users
biff	be notified if mail arrives and who sent it
chfn	change finger entry
finger	lists informaiton about users	finger username
from	see who your mail is from
mesg	permit or deny messages from write and talk	mesg y
pine	mail program
talk	"talk" to another currently logged in user: talk username	talk username
who	list who is on the system
write	send an interactive message to another user	write username
Dealing with the File System
cat	concatenate and display arguments to standard output	cat file
cd	change directory  Note: given a full or relative path, set the working directory as specified; without arguments set the working directory to the login directory.	cd path
cp	copy files	cp fromfile tofile
diff	compares two files and reports the differences	diff file1 file2
du	gives the number of kilobytes contained in files and directories
ispell	check the spelling of the contents of a file	ispell file
lpr	send a job to a printer  Basic Options:  -Pprinter specifies which printer -Bbin specifies the bin -Nnote print note on burster page -m send mail upon completion	lpr [options] file
ls	list the contents of a directory  Basic Options:  -a  all files -F mark directories with /, executable files with *, symbolic links with @, and sockets with = -l Long listing showing protections, number of links, owner, size in bytes, and time of last modification -g with -l shows group ownership -s size in kilobytes	ls [options] file
mkdir	create a new subdirectory in the current directory	mkdir subdir
more	browse or page through a text file.  Usage: press the space bar to go forward a page and type b to go back a page.	more file
mv	move or rename filesmv fromfile tofile	mv fromfile tofile
printers	show printers available on Rutgers systems
pwd	display the current directory's full pathname
quota -v	display the disk usage and limits. Use the  command without the option to display warnings only.
rm	remove (delete) files  Note: Once a file is deleted, you can't undelete it. Use the -i option to have Unix ask if you are sure about removing the file.	rm [option] file
rmdir	remove empty directories	rmdir dirname
Languages
adb	general purpose program debugger	adb objectcode
cc	C compiler	cc file.c
dbx	program debugger	dbx executable
f77	Fortran 77 compiler	f77 file.f
lint	attempts to detect features of C programs that are likely to be errors, non-portable, or wasteful	lint file.c
make	facilitates compilation of several program modules
pc	Pascal compiler	pc.file.p
Work Environment
clear	clear the terminal screen
passwd	change the login password
reset	reset the terminal screen
script	make a copy of everything displayed on the screen Usage: to end scripting, type a <CTRL>d;  Note: useful for capturing error messages and program execution.	script filename
Editors and Text Formatters
emacs	the emacs editor	emacs [filename]
latex/tex	test formatting and typesetting
teach-emacs	the emacs online tutorial
Communications
ftp	transfer files between networked systems	ftp computer
kermit	kermit file transfer
telnet	login on another computer on the network	telnet computer
News Programs
lookfor	find a newsgroup using a keyword search
nn	newsreading program
postnews	news posting utility

For More Information