Getting started in Unix
Overview
This is an older document that is presented here for information purposes. It is not regularly updated and some information may be dated or incorrect. Caveat emptor.
Getting Started in UNIX
Getting Started in UNIX
September 1994
Stanford University
======================================================================
Contents:
Part I: Before You Begin
Part II: Beginning Unix
Essential Information
Logging In and Out
Getting Information
Part III: Working with Files and Directories
Managing Directories
Managing Files
Advanced Procedures
Non-AFS Security
AFS Security
Part IV: The Shell Program
Customizing Your Session: Defining Your Shell Environment
Re-Directing I/O and Building Pipes between Commands
Controlling Jobs
Keeping Command History
Part V: Using EMACS
Part VI: Printing
Part VII: Staying Informed about System Activity
Appendix A: UNIX Command Summary
Appendix B: Using Compilers-A Quick Guide
Copyright 1994 by the Board of Trustees of Leland Stanford Junior
University
Part I: Before You Begin
========================
What is UNIX? Every computer-mainframe, workstation, or microcomputer-
has an operating system that allows the users and the computer to
interact. As an operating system, UNIX is responsible for managing
computer resources and allocating and scheduling these resources to
serve the needs of individual users. Developed at Bell Laboratories in
the early 1970's, UNIX (a registered trademark of AT&T Bell
Laboratories) originally ran on a DEC PDP-11 computer. After the
introduction of the DEC VAX computer, UNIX was modified to run on it.
As University of California at Berkeley made many enhancements, their
version of UNIX began to diverge from the Bell Labs version. Today
there are many different versions of UNIX.
Why UNIX? With its programming tools, application programs, and
networking facilities, UNIX provides a powerful, versatile computing
environment. Use of UNIX is widespread, and with the advent of UNIX
workstations, it continues to grow in popularity. Why then is UNIX
desirable?
* UNIX is a general purpose, multi-tasking (capable of handling
multiple requests simultaneously), multi-user, interactive operating
system.
* Since most of UNIX is written in a high level language, it can run on
many different computer systems.
* There is a wide variety of applications compatible with UNIX.
About This Document: Getting Started in UNIX explains fundamental UNIX
concepts, providing the novice user with the information necessary to
use basic UNIX commands, to run a few useful programs, and to manipulate
files effectively. The Leland Systems at Stanford University are
distributed UNIX systems that include workstations from DEC, IBM and
Sun, found on the second floor of Sweet Hall; Cardinal, a DEC 5000/240
compute server; Leland, a DEC 5000/240 mail server; and Power and
Wisdom, the UNIX systems for the Social Sciences. Information in this
document applies to all these systems.
Part II of Getting Started in UNIX takes you through an initial UNIX
session, teaching you how to log in, give the computer some simple
commands, and log out. Subsequent sections describe the following
commonly-used procedures:
* working with files and directories,
* using the shell (the program that reads your commands and invokes
programs to carry them out),
* editing text files, and
* printing.
Sample Sessions: Throughout this document, sample sessions show what
you would see on your monitor during relevant work sessions. Sample
sessions include prompts and commands. The UNIX system uses a prompt to
tell you it's ready to accept your next command. This prompt is usually
the name of the computer followed by >, e.g., elaine24>. In sample
sessions, the commands you type appear in bold type, and what UNIX
displays on the screen is in normal type. Thus, in the sample session
on page 2, you would type date only. Text on the right side of the page
is additional commentary or more detailed instruction to help clarify
the example. In this sample session, the text explains that you must
press the RETURN key after typing date. Special function keys on your
keyboard, like RETURN, are shown in all capital letters and in bold
type.
elaine24> date After you type date, press the
Thu July 7 8:38:25 PDT 1990 RETURN key.
If what appears on the screen during a sample session is lengthy, it may
be abbreviated within angle brackets to conserve space, e.g., . The first sample session in the Logging In section of Part
II contains this example.
Other Documents: Throughout Getting Started in UNIX, references are
made to some of the other documents available on the second floor of
Sweet Hall;. Most of these documents are available in their original
formats through any Macintosh connected to SUNet. From the Chooser,
open the Computing Distribution file server in the Stanford zone,
register as a guest, and open the Computing Documents folder and then
the Sweet Hall Documents folder. Most UNIX documents are also available
in text-only format directly through the distributed UNIX systems. Type
help docs at the system prompt for a menu of which documents are
currently available.
Getting Help: If you have questions about using the Leland Systems;,
contact the consultants; on the second floor of Sweet Hall at 725-2101.
You can also send computing questions to the consultants via computer,
using the electronic mail address consult@leland.
Part II: Beginning UNIX
=======================
About Part II: Part II shows you how to access a UNIX host, begin and
end a work session, set your terminal type, change your password, and
get help when you need it.
Usually people share a UNIX computer system, called a host. Each person
must have an account; accounts provide a necessary means of regulating
each person's use of the system. A username and password identify an
account. Your username is the way you identify yourself to the system;
your password verifies your identity. The document Introduction to the
Leland Systems tells you how to open a UNIX account on the Leland
Systems.
Essential Information
---------------------
Commands: Commands are directions you give to the computer. They are
usually English words or abbreviations. To give the computer a
commands, type the command name and press RETURN. For example, if you
type the command date at the prompt and press RETURN, the computer
displays today's date on your screen.
Arguments and Options: Many UNIX commands allow you to attach one or
more arguments. Arguments determine the way in which the command
carries out its function. Names of computer files, time limits, and
other information that constrains or defines the scope of a command are
arguments. For example, the command cd tells the computer to change
from the current directory to another one. To move to a subdirectory
named Mbox, you would use its name as an argument to the change
directory command, i.e., cd Mbox. Mbox would then become your working
directory.
An option is a special kind of argument preceded by a hyphen (-). It
tells the computer to execute a particular variation of the command.
For example, ls tells the computer to list the files and subdirectories
contained in your working directory; ls -l tells the computer to list
them with additional information about each file.
Command Sequences: There are many command sequences that are helpful
when you use UNIX. Control sequences, for example, are used extensively
in EMACS, a popular text editor, as well as in the normal UNIX shell.
To type a control sequences, hold down the CONTROL key and type the
designated letter. Control sequences are represented in this document
as C-x. To enter the command C-c, you would hold down the CONTROL key
while you type c.
The ESCAPE key is used in a similar manner, but instead of holding down
the ESCAPE key while hitting another key, you hit them one after the
other. Escape sequences are represented as ESC x. To enter the command
ESC f, you would press the ESCAPE key and then type f.escape sequences
The following keys and command sequences may prove especially useful to
you when you are first using UNIX:
DELETE or erases the last character you typed.
BACKSPACE
C-c stops or interrupts a program
currently running.
C-s freezes the program's output on the
screen (but the program may continue
to run).
C-q unfreezes the output suspended by
C-s.
IMPORTANT NOTE
--------------
UNIX is case sensitive. That is, UNIX differentiates between upper case
and lower case letters. Therefore, typing Open is not the same as
typing open or OPEN. Pay special attention to case when you use UNIX.
Logging In and Out
------------------
Logging In: Your Leland Systems account allows you to log in to one of
the distributed UNIX systems. These include Cardinal, the DEC 5000/240
that has replaced Leland for direct logins, and all of the UNIX
workstations listed below. (Power and Wisdom are available only to
authorized users in the Social Sciences departments.) logging in
Workstation type Login to
---------------- --------
DECstations adelbert1-adelbert26
IBM RS/6000s rs1-rs13
Sun SPARCstations elaine1-elaine54
To begin a work session, type your username and password. Notice that
your password does not display on the screen as you type it. This is
added protection provided by the UNIX system so that curious eyes cannot
read your password. If you make a mistake, you must type both your
username and password again. You are given several chances to type them
in correctly, after which you will be disconnected. Once you
successfully log in, the system displays its prompt and waits for your
commands.
login: tsoi Type your username.
Password: Type your password.
DSO AFS (R) 3.2 Login
Last login: Thu July 7 16:52:01 from 36.83.0.150
Sun SPARCstation 2, SunOS 4.1.2, 32MB RAM, 190MB swap
-------------------------------------------------------------------
Mail questions to consult@leland; mail problems to action@leland.
-------------------------------------------------------------------
System messages may appear here.
These messages tell you about any
changes in the system you are using.
elaine24.Stanford.EDU>
Setting the Terminal Type: When you set your terminal type, you tell
the UNIX system what type of display you are using. Each time you
connect to a UNIX system, you should set the terminal type. Use the
command set with the argument term=terminal type. Following is a list
of the terminal type command settings for microcomputers and
workstations:
DECstation set term=xterm
IBM RS/6000 set term=xterm
Microcomputer set term=vt100
SPARCstation with the X Window set term=xterm
System, Version 11
SPARCstation without the set term=sun
X Window System
To make setting the terminal occur automatically at the beginning of
every work session, follow the procedure in Customizing Your Session on
page 15.
Window Systems: If you are using a workstation console in Sweet Hall,
you may use a window system, such as X. (You automatically enter the X
Window System when you log in to a DECstation.) A window system is a
collection of software that makes it easy for you to take full advantage
of the graphics and display capabilities of a workstation. Different
window systems are available on each type of workstation; to see which
systems you can use on your workstation and how to activate them,
consult the Tips sheet posted in the cubicle where you are working. For
details on the X Window System, the most widely used of the available
windowing systems, see Using the X Window System;.
A Note About AFS: Many Leland Systems accounts (including all Power and
Wisdom accounts) are AFS-based UNIX accounts AFS-based accounts (as
opposed to NFS-based accounts). (If the pwd command says your home
directory is in /afs/ir, you have an AFS account.) AFS is a method by
which different computers may share the same files, conserving disk
space and making a wider variety of computers available to each user.
Because of the increased file security offered by AFS, extremely long
login sessions and extremely long-running programs (longer than 25
hours) may be problematic. For information on how to successfully run
programs requiring more than 25 hours of real time, contact a consultant
at 725-2101 or send mail to consult@leland.
Changing Your Password: You may want to change your password
occasionally to preserve the security of your account. (You cannot
change your username after you have opened your account.) Your password
must not be any word found in the English dictionary, your username, or
any permutation of your name or initials. It is recommended that your
password be a combination of letters and numbers. You can change your
password with the password command at the system prompt. Remember, when
you type your password, it won't appear on the screen.
elaine24> password
Changing password for tsoi
Old password: Type your old password.
New password: Type your new password.
Retype new password: Type your new password again.
Logging Out: Logging out ends your work session. If you do not log out
when finished, someone else can continue working on the computer with
your account. If a message on the screen indicates there are stopped
jobs, be sure to 'kill' them before logging out. See Controlling Jobs
on page 19.logging out
elaine24> logout Type logout.
Getting Information
-------------------
The UNIX Online Manual: The reference manual for the Leland Systems is
online;, so you can get descriptions of UNIX commands as needed. The
man and apropos commands give you access to the online reference manual.
The manual is organized by command; as a novice, you may find that the
difficulty is knowing which command you need to read about. As shown in
the following sample session, you can use the -k option with man to
obtain a list of topics related to a particular key word. UNIX online
manual
elaine24> man man This displays the section of the
manual describing the manual display
program itself. Press the space bar
to display the next screenful of
information. Type q to leave the
manual and return to the system
prompt.
MAN(1) USER COMMANDS MAN(1)
NAME
man - display reference manual pages; find reference pages
by keyword
SYNOPSIS
man [-] [-t] [-M path] [-T macro-package] [[section] title
elaine24> man -k password This shows all commands associated
with the keyword password. Same as
the command apropos password.
crypt, _crypt, setkey, encrypt (3) - password and data encryption
getpass (3V) - read a password
elaine24> man password This displays the section of the
manual describing the command
password.
PASSWorD (1) USER COMMANDS PASSWD (1)
NAME
password - change local or NIS password information
SYNOPSIS
password [ -l | -y ] [ -afs ] [ -d [ username ] ] [ -e username ]
[ -F filename ] [ -n numdays username ]
[ -x numdays username ] [ username ]
Most commands in UNIX run programs; you can find documentation for
almost all of these commands with man command. However, some commands
are built into the shell program; you can find documentation for these
commands with man tcsh. For more information about the shell program,
see Part IV.
Online Tutorials: You can also learn more about UNIX by typing learn at
the system prompt. It will show you a menu of tutorials that are
available and give instructions on how to use them. Note that the learn
tutorial does not cover information specific to AFS-based accounts. If
you are using an AFS-based account, the information under the files
topic will be largely accurate but incomplete. For more information on
AFS-based topics issue the command cd ~consult to access the file in the
consult directory. Change to the pub directory and then to afs, and
consult the file afsguide.
Other Sources: Printed copies of UNIX and workstation manuals are
located on the second floor of Sweet Hall for your reference. Printed
and online versions of UNIX documents are also available. See Other
Documents on page 2 for details. And, as stated earlier, the
consultants can answer questions about the Leland Systems;. If you need
help, contact the consultants on the second floor of Sweet Hall at 725-
2101, or send a message to the electronic mail address consult@leland.
Part III: Working With Files and Directories
============================================
About Part III: The first three sections of Part III show you how to
create and organize UNIX files and directories. A file is a data set,
such as a chart or an essay, that is saved under a particular title.
You can open a saved file at any time to edit or print its contents.
All work you do while using a UNIX system must be saved to a file or it
will be lost when you log out. When you open a particular file, all
commands you issue will apply to that file, unless you specify
otherwise.
Directories are basically "folders" used to organize files and other
directories. When no files are open, all commands you issue will
operate on the directory you are currently in unless you specify
otherwise. Once you are logged in to your account, you will need to
navigate among the directories to find the files and programs you want
to use.
The last two sections of Part III explain the procedures for securing
your files and directories. UNIX gives you the ability to protect your
work as you see fit. You decide what you can do to your work, and what
others can do to it. The UNIX security system allows you some control
over who can see, alter, and use your files and directories.
Managing Directories
--------------------
Directories and files are organized hierarchically, in the shape of an
inverted tree. Below is a diagram of a simplified filesystem.
Directories are represented with a slash (/).
/
|
--------------------------------------------
| | | |
usr/ etc/ student/ ps/
| | |
------------ ------------ faculty/
| | | |
class/ adm jones/ barney/
| | |
------------ ------------ work
| | | |
cs240a cs243 docfiles/ datafiles/
|
------------
| |
sample.doc other.doc
Most of the examples in this section use the directories and files
listed in this diagram.
The Root Directory: The / at the top of the diagram is the root
directory for the filesystem as a whole. This sample root directory
contains four other directories, usr, etc, student and ps. Such
directories-within-a-directory are called subdirectories. Every file on
the system is contained directly or indirectly (through a subdirectory)
in the root directory.
Your Home Directory: When you first login to a UNIX system, you are
initially in your home directory, the directory that holds your personal
files. In the diagram above, the home directory of the user named Jones
is /student/jones. Because of the large number of accounts on the
Leland Systems, actual home directories have longer names and are more
deeply nested. A student account rjones may have a home directory like
/s7/r/rjones or /afs/ir/users/r/rjones.
Your Working Directory: Whenever you use a UNIX system, you are working
within a specific directory. That directory is your working directory.
For example, if you were in the /jones directory in the diagram, your
working directory would be /student/jones. Because most commands that
operate on directories will affect your working directory (unless you
specify otherwise), it's important to know what the working directory
is. To find out, use the pwd (print working directory) command:
elaine24> pwd Prints the working directory, that
is, lists the name of the working
/student/jones directory on the screen.
Creating a Directory: You can create a new directory at any time with
the mkdir command. When you use this command, a new directory with the
specified name will appear within your working directory. (You may want
to distinguish your directory and file names so you can differentiate
them easily. One method is to begin each directory name with an
uppercase letter and each file name with a lowercase letter.)
elaine24> mkdir Test Creates a directory named Test in
the working directory.
Moving Among Directories: You can move from one directory to another
with the cd (change directory) command, using the name of the new
directory as the argument. When you use the cd command with no
argument, you move directly to your home directory.
elaine24> cd docfiles Changes from the current working
directory (jones) to docfiles, which
becomes the new working directory.
elaine24> pwd
/student/jones/docfiles
This method lets you move down one directory, that is, from the working
directory to one of its subdirectories. To move up one directory, use
.. (two periods) as the argument to cd.
elaine24> cd .. Changes to the directory one level
above, in this case back up to
jones.
elaine24> pwd
/student/jones
To move further than one level at a time, you must list each directory
along the way, separating them by slashes.
elaine24> cd /jones/docfiles Changes directory from student to
docfiles, two levels below.
elaine24> pwd
/student/jones/docfiles
elaine24> cd ../datafiles Moves back up one level to jones,
and then down to datafiles, a
directory that is parallel to
docfiles.
elaine24> pwd
/student/jones/datafiles
Removing a Directory: You remove a directory with the rmdir (remove
directory) command, using the directory name as the argument. This
command will not work if there are any files or other directories within
the directory you wish to remove.
elaine24> rmdir docfiles The directory docfiles is removed
from the working directory.
If you wish to remove a directory and all of its contents, use the
option -r. Make sure that you actually want to delete everything in
this directory before you execute this command!
elaine24> rmdir -r docfiles docfiles is removed, along with
everything inside it. Use with
caution! The advantage is that you
don't have to empty the directory
first.
Displaying a Directory's Contents: The ls command lists the files and
subdirectories contained in the specified directory. As shown in the
following sample sessions, different information displays depending on
what arguments and options you use.
elaine24> ls Lists the names of files and
Air Class Mail a.out bin subdirectories in the working
directory. UNIX alphabetically
orders files and directories with
initial uppercase letters first,
then with initial lowercase letters.
elaine24> ls /usr Lists the names of files or
2020 crash ingres subdirectories in a directory other
adm dict kernels than the current one, in this case
athena doc lib /usr.
bin etc local
blss field lost+found
elaine24> ls -l Using ls with the -l
drwx------ 4 tsoi 512 May 16 08:36 Air option lists each
drwx------ 9 tsoi 512 May 11 10:49 Class file or directory in
drwx------ 9 tsoi 1024 May 19 13:36 Mail the working
drwx------ 9 tsoi 512 May 11 10:49 a.out directory, along with
drwxr-xr-x 3 tsoi 512 May 18 23:46 bin its permissions
(security informa-
tion), creator, size
in bytes, and date of
last modification.
elaine24> ls -F Lists what's in the working
Air/ Class/ Mail/ a.out* bin/ directory, specifying the
file types. The character /
after a name indicates a
directory; * indicates a
program you can run.
elaine24> ls -a Lists all files, including dot
.cshrc .logout a.out files. (Dot files are explained
.forward .plan bin below, under Managing Files.)
.login Class mail
Managing Files
--------------
Viewing Files: You can use the more, less and page commands to display
a file's contents one screenful at a time. To display the next
screenful, press the space bar. All three commands scroll the text as
they display the next screenful. To learn the differences among these
commands, type man more, man page, or man less as appropriate.
elaine24> more longfile Scrolls the contents of the file
longfile, screen by screen.
Press the space bar to display the
next screenful. To return to the
prompt, use C-c command.
Sometimes you might like to see just a few lines at the top or bottom of
a file in order to check on its contents. The head command displays the
first ten lines of a particular file, and the tail command displays its
last ten lines. Both allow you to specify the exact number of lines to
display with the -n option (where n is the number of lines to display).
elaine24> head todo.list Displays the first 10 lines of the
file todo.list.
TODO LIST: 1. wash cars
2. put out trash
:
10. deposit check
elaine24> tail -5 todo.list Displays the last 5 lines of the
file todo.list.
13. reserve tennis court
:
17. write up documentation
Moving and Renaming Files: The mv command either gives a file a new
name or moves it to a new location. Its first argument is always the
file you are moving or renaming. Its second argument is the destination
directory (the directory where the file should be moved), along with the
new name of the file. If only a directory is given as the second
argument, the file is moved into that directory with the same file name.
If only a new filename is given, the newly named file stays in its
current directory.
elaine24> mv mbox Oldmail Moves the file mbox into the
directory Oldmail.
elaine24> mv supplies toget.list Gives the file supplies the new name
toget.list.
elaine24> mv mbox Oldmail/xbox Moves the file mbox into the
directory Oldmail, and changes its
name to xbox.
Copying Files: The command to copy files is cp. It functions in
exactly the same manner as mv. The only difference is that it creates a
duplicate of an existing file, leaving the original file untouched. It
helps to give the new file a different name from the original file in
order to avoid confusion.
elaine24> cp mbox xbox In the working directory, creates a
copy of the file mbox and calls it
xbox.
elaine24> cp mbox Oldmail/xbox Copies the file mbox from the
working directory to the Oldmail
directory, and calls the new file
xbox.
IMPORTANT NOTE
--------------
When copying, moving or renaming a file, make sure that no other file
with the same name already exists in the destination directory. UNIX
does not warn you if you are using the same name for two different
files. If you try to place a file in a directory where another file
with that name exists, the old file will be permanently removed and
replaced by the new file.
Removing Files: The command rm removes files permanently. To be safe,
use the option -i with the rm command and the computer will ask if
you're sure you want to remove the file before proceeding.
elaine24> rm junk.old Removes the file junk.old
permanently.
elaine24> rm -i test.doc Removes the file test.doc; the
computer asks for confirmation.
rm: remove test.doc? y You type y for yes or n for no.
Dot Files: Within your home directory are several files whose names
begin with a dot (or period). Most users don't need to access dot files
often. They don't appear when you issue the ls command (unless you use
the -a option). You can create and remove dot files in any directory
just as you can normal files.
Some Common Dot Files:
.cshrc file The system runs the commands in this file each time you
start a shell. Usually a good place for alias commands.
See Customizing Your Session on page 15.
.login file The system runs the commands in this file when you
login. See Customizing Your Session on page 15.
.plan Optional files you create that contain personal or work-
related information of an arbitrary nature that is
.project displayed when your username is fingered. See Finding
Out About Other Users on page 25.
Advanced Procedures
-------------------
Absolute and Relative Pathnames: Pathnames give the locations of the
files and directories you refer to in your command statements. They act
as road maps, telling the computer exactly where to go to find the
information you need. The absolute pathname tells where something is in
relation to the root directory of the filesystem, listing every
subdirectory along the way. For example, the absolute pathname for the
file sample.doc from the diagram on page 6 is
/student/jones/docfiles/sample.doc.
Just as absolute pathnames use the root directory as their reference
point, relative pathnames use the working directory as their base.
Relative pathnames give directions to a directory or file according to
its location in relation to the working directory. Using the same
diagram, if you are in the jones directory and wish to refer to the file
sample.doc, you would use the pathname that gives the file's location
relative to the jones directory, docfiles/sample.doc. Relative
pathnames are useful in complicated filesystems with deeply nested
directories and files. Note that relative pathnames never begin with /
because their origin is the working directory and not the root
directory.
The following examples are also based on the diagram on page 6.
elaine24> pwd The working directory is docfiles.
/student/jones/docfiles
elaine24> cp other.doc ../datafiles Copies other.doc to the directory
datafiles, using its relative
pathname. It would have been more
troublesome to use the absolute
pathname, which is
/student/jones/datafiles
elaine24> pwd The working directory is barney.
/student/barney
elaine24> cp work /ps/faculty Copies the file work to the
directory faculty, using the
absolute pathname. In this case, it
would have been more troublesome to
use its relative pathname,
../../ps/faculty.
Periods as Shorthand: In the cases when you want to use the working
directory as an argument for a command, you can use a period as the
shorthand term for it. If the working directory is /ps/faculty, you
could refer to it with . in the argument to the copy command cp.
elaine24> cp /student/jones/docfiles/sample.doc . Uses the absolute
pathname of the file
sample.doc to copy it
to the working
directory, referred
to with a period.
As stated earlier, .. (two periods) is used to refer to the directory
one level above the working directory.
Referring to Groups of Files: The shell recognizes some special
characters associated with file names. Use these characters to specify
groups of files easily.
The Character What It Means
------------- -------------
* refers to any string of characters.
? refers to any single character.
~ has special meaning when associated
with a username as in ~jones. In
these cases this refers to the user
jones' home directory. Thus,
~jones/.login refers to the file
.login in jones' home directory.
Also, you can use ~ to refer to your
home directory.
[ ] indicates any single characters
included in the brackets.
Examples
elaine24> ls *.c Lists all files whose names end with
disk.c drum.c main.c .c.
elaine24> ls d*.c Lists all file names beginning with
disk.c drum.c d and ending with .c.
elaine24> ls main.? Lists all files beginning with main
main.c main.h and ending in any single character.
elaine24> ls *.[ch] Lists all files ending in either .c
disk.c globals.h or .h.
disk.h main.c
drum.c main.h
drum.h
elaine24> ls ~jones Lists all files in the home
Work mbox bin directory for jones.
Transferring Files Between Computers: The FTP Program allows you to
send or receive copies of files to or from another computer. It is
available on all of the Leland Systems; and on most microcomputers and
workstations connected to SUNet. (The FTP Program may not work on all
systems if you have an AFS account.)
The following instructions explain how to transfer files between UNIX
hosts. The ftp command takes the remote computer name (the name of the
other computer involved in the transfer) as its argument. You initiate
an FTP transaction by identifying yourself to the remote computer with
your username and password on that system. (To use anonymous FTP, type
anonymous as the username and your username as the password.) You can
then move to any directory on the remote computer with the cd command.
Use the command send to transfer a file from your computer to the remote
computer. The file you wish to transfer must be in your working
directory; it will appear in the directory you have specified in the
remote computer. Use the command get to transfer a file from the remote
computer to your computer. The file you wish to receive must be in the
working directory of the remote computer; it will appear in your working
directory. Leave the FTP program with the command quit; the normal
system prompt reappears.
elaine24> ftp jessica Initiates file transfer with the
Connected to jessica.stanford.edu. remote computer Jessica.
220 jessica.stanford.edu FTP server (Version 4.169 Fri May 26 12:12:25
PDT 1989) ready.
Name (jessica:kath): ksteele Requires the username for your
account on Jessica.
Password (jessica:ksteele): Requires the password for your
account on Jessica.
331 Password required for ksteele.
230 User ksteele logged in.
ftp> send SOC22 Copies the file SOC22 from your
computer to the remote computer.
200 PORT command successful.
150 Opening ASCII mode data connection for SOC22.
226 Transfer complete.
local: SOC22 remote: SOC22
56970 bytes sent in 0.84 seconds (66 Kbytes/s)
ftp> get SOC23 Copies the file SOC23 from the
remote computer to your computer.
200 PORT command successful.
150 Opening ASCII mode data connection for SOC22 (55706 bytes).
226 Transfer complete.
local: SOC23 remote: SOC23
56970 bytes received in 0.86 seconds (65 Kbytes/s)
ftp> quit Ends the FTP program.
221 Goodbye.
elaine24>
Non-AFS Security
----------------
Note: The information on UNIX file access permissions does not apply to
AFS-based accounts. Likewise, the information on AFS access control
lists does not apply to non-AFS accounts. There are some exceptions,
such as the directory /tmp. On all systems, /tmp is governed by non-AFS
file access permissions. Be sure to refer to the section that applies
to you.
Users: In the UNIX environment, those who may access a particular file
or directory are divided into these three classes:
owner the user who owns the file or directory
group the group of users who share access to a file. (Every user
belongs to a group. In general, students all belong to the
student group. To see what group you are in, type groups at
the system prompt.)
other all other users
Access Permissions: When you create a file or directory, it is assigned
a default set of permissions that control access to it. You can change
these permissions. For each class of users, the following three
permissions may be granted for each file or directory:
Permission File Directory
read (r) Allows you to read the file. Allows you to list the
files and subdirectories in
the directory.
write (w) Allows you to create, delete Allows you to create and
and modify the file. delete files in the
directory, since this
requires writing to the
actual directory.
execute (x) Allows you to run a file. Allows you to list only the
files whose names you
specify, not the directory
itself. Therefore, you can
list only the files whose
names you know. For
example, if the directory
tmpdir had execute
permission only and you
typed ls -l tmpdir, you
would get no result.
However, if you typed
ls -l tmpdir/workfile,
information about workfile
would be displayed.
Displaying a File's Permissions: With the command ls -l, you can see
the permissions associated with a particular file as the first 10
characters on each line.
elaine24> ls -l
drwxrwxr-x 5 tsoi 512 Feb 23 09:30 MyPublicDir
-rw-r----- 5 tsoi 512 Feb 22 14:30 intro.unix
-rwxr-xr-x 5 tsoi 512 Feb 22 16:30 a.out
The first character indicates whether this file is a directory (d) or
just a regular file (-). The next nine characters are three groups of
three characters each. These are the permissions granted for the owner,
group, and other user classes, respectively. A permission is granted if
the letter is present, and not granted if a hyphen is there instead.
Thus, in the example above, the file intro.unix is a regular file (-)
that allows the owner reading and writing privileges (rw-), but limits
the group to reading privileges only (r--). Other users are not allowed
to do anything with this file (---), and execution privileges are not
allowed for any class of users.
Note that even if another user has access to a particular file, he or
she will be unable to use such privileges if they do not have access to
the directory in which the file is located. Be sure to grant such
access to all of the directories in a file's path that are under your
control.
Making Security Changes: You can change the permissions associated with
a file with the chmod command. Users are identified by letters when you
use chmod: the owner is u, the group is g, others are o, and a
represents all users. You literally add or take away permissions with
the + and - signs. The file which you are securing is the command's
final argument.security changes
elaine24> ls -l
total 3
-rwx------ 1 tsoi 40234 May 23 14:50 myunix.doc
-rw-rw-rwx 1 tsoi 645 May 23 14:20 script
-rw-r----- 1 tsoi 974 May 23 09:24 xcomments
elaine24> chmod a+r myunix.doc Grants read access to all (a).
elaine24> chmod a-w script Denies write access to all.
elaine24> chmod g+w xcomments Grants write access for the group
(g).
elaine24> chmod u+x,o-x script Grants execute right for the owner
(u), and removes execute right for
other (o) class.
elaine24> ls -l
total 3
-rwxr--r-- 1 tsoi 40234 May 23 14:50 myunix.doc
-r-xr--r-- 1 tsoi 645 May 23 14:20 script
-rw-rw---- 1 tsoi 974 May 23 09:24 xcomments
elaine24>
Security Changes Shortcut: You can also use a three digit number
argument to the chmod command in order to accomplish changes in
permissions in fewer steps. The three digits of the argument, for
example, 421, specify the owner's (4), the group's (2) and the other
users' (1) permissions respectively. Each digit in the argument is a
sum of a possible three numbers corresponding to the access privileges
granted to that user class:
read access add 4 to sum
write access add 2 to sum
execute access add 1 to sum
For example, if you wanted to grant read and write access for one of the
user classes, you would add the read access value, 4, to the write
access value, 2, and get a result of 6. This would be the digit you
would use in the appropriate place (for the correct user class) in the
three digit number in the chmod command.
elaine24> chmod 644 .login The owner can read and write;
everyone else can only read.
elaine24> ls -l .login
-rw-r--r-- 1 tsoi 796 May 7 18:11 .login
elaine24> chmod 740 myscript Lets the owner read, write and
execute; lets the group read; grants
no privileges to others.
elaine24> ls -l myscript
-rwxr----- 1 tsoi 356 May 7 10:30 myscript
AFS Security
------------
Many Leland Systems accounts, including all Power and Wisdom accounts,
are AFS-based UNIX accounts (as opposed to NFS-based accounts). (If the
pwd command says your home directory is in /afs/ir, you have an AFS
account.) AFS is a method by which different computers may share the
same files, conserving disk space and making a wider variety of
computers available to each user. If your account is an AFS-based
account, you have additional control over exactly what type of access
you wish to give to individual users or groups of users on your system
or on other AFS-based systems. Eventually, all Leland Systems accounts
will move to AFS.
Note: The information on UNIX file access permissions does not apply to
AFS-based accounts. Likewise, the information on AFS access control
lists does not apply to non-AFS accounts. There are some exceptions,
such as the directory /tmp. On all systems, /tmp is governed by non-AFS
file access permissions. Be sure to refer to the section that applies
to you. File permissions for owner are always governed by non-AFS
rules.
Access Rights: Each directory in AFS has an Access Control List (ACL)
associated with it. The ACL grants different users or groups of users
different types of access rights for the files contained in the
directory. As the owner of a directory, you may determine precisely
which rights you grant to which users. The seven access rights and
their one letter codes are:
(r) Read allows a user to read the contents of any file in the
directory. Files that are meant to be private must be placed in
a separate directory or subdirectory.
(w) Write allows a user to modify the contents of any existing file
in the directory.
(k) Lock allows a user to flock a file. Certain programs use this
method to ensure that two processes do not try to write to the
same file at the same moment.
(l) Lookup allows a user to list the names of the files and
subdirectories in a directory, and to examine the ACL for a
directory. Lookup also controls access to subdirectories. For
a user to have access to a subdirectory, she must have the
Lookup right for its parent directory. Note that Lookup does
not allow a user to read the contents of a file in the
directory.
(i) Insert allows a user to add new files to the directory and to
create new subdirectories. It does not allow the user to change
the contents of existing files in the directory.
(d) Delete allows a user to remove files and subdirectories from a
directory.
(a) Administer allows a user to change the ACL for a directory.
Users always have this right for their home directories and
their subdirectories, even if they remove themselves from the
ACLs.
Examining the ACL for a directory: You must have the Lookup right for a
directory to be able to examine its ACL. Use the fs listacl command to
examine the access control list for a given directory. Here we examine
the ACL for the current directory, ".":
power-[1> fs listacl .
Access list for . is
Normal rights:
system:anyuser rl
rjones rlidwka
power-[2>
This indicates that any user may list the contents of this directory and
read the files in the directory. The user rjones has all access rights
for the directory. This is the default ACL for the user rjones' home
directory on many AFS systems. On some systems (including Power and
Wisdom), system:anyuser is granted only the Lookup right. This way, the
contents of the files in a user's home directory are hidden from other
users.
The regular UNIX access permissions for a file or directory may be
viewed using the command ls -l. However, these UNIX access permissions
have very little effect on user access to the file or directory. AFS
file access rights override UNIX permissions in most cases.
Making Security Changes: The fs setacl command allows a user to change
the ACL for any directory for which he or she has the Administer right.
In the following sample session, the user rjones creates a project
subdirectory, and grants two other users, buzz and pjames, the (l)
Lookup, (r) Read and (i) Insert rights.security changes
power-[2> fs listacl .
Access list for . is
Normal rights:
system:anyuser l
rjones rlidwka
power-[3> mkdir project Creates project directory.
power-[4> fs listacl project
Access list for project is
Normal rights: Note that the project directory
system:anyuser l was, by default, created with the
rjones rlidwka same ACL as its parent directory.
power-[5> fs setacl project buzz rli Grants Read, Lookup, and Insert
power-[6> fs setacl project pjames rli rights to buzz and pjames for the
power-[7> fs listacl project project directory.
Access list for project is
Normal rights:
system:anyuser l
buzz rli
pjames rli
rjones rlidwka
Before giving buzz and pjames access rights to the project directory in
the example above, rjones first verified that all users had the Lookup
right for his home directory. Remember, without the Lookup right for a
directory, users cannot access any of that directory's subdirectories,
regardless of how the ACLs are set for those subdirectories.
Part IV: The Shell Program
==========================
About Part IV: As soon as you log in, the shell program activates.
Providing the interface between you and the UNIX system, the shell is
the program that reads your commands and invokes other programs to carry
them out. The first section of Part IV teaches you how to customize
your shell environment. The second section describes how to maneuver
the input and output (I/O) of your commands in the shell environment in
order to access files and issue commands more effectively. The third
section explains how to handle multiple jobs at once. (A job is the
process you set in motion when you issue a command.) The final section
describes command histories and how you can use them.
Customizing Your Session: Defining Your Shell Environment
---------------------------------------------------------
About the Shell Program: The shell program used on all Leland Systems
computers is the tcsh shell. (You can obtain full documentation about
this shell with man tcsh.) You invoke the shell program when you login;
it displays the system prompt when it is ready for your input.
Throughout your UNIX session, the shell program acts as a liaison
between you and the computer, translating your commands so the computer
can execute them, and translating the computer's output so you can
understand it.
The first time you invoke the shell program, it is called your login
shell. To leave the login shell, you use the logout command. During a
work session, you may invoke the shell program again when you use
certain commands, e.g., script. A change in the default prompt may
indicate that you have invoked the shell program again. To leave a
shell that is not the login shell, use the exit command.
Setting Shell Variables: Shell variables help to determine how the
shell program interacts with you. You can create your own shell
variables and assign them values with the set command. You can then use
the variable in a command line by prefixing the variable name with the $
symbol.
elaine24> set workdir=/student/jones/Work Creates the variable workdir
to represent the directory
/student/jones/Work. You must use
its absolute pathname.
elaine24> echo $workdir Shows the value assigned to workdir.
/student/jones/Work
elaine24> cd $workdir Changes from the working directory
to the workdir.
elaine24> unset workdir Removes the shell variable workdir.
Now, you can no longer
use workdir to refer to
/student/jones/Work.
The procedure shown in the preceding sample session sets the shell
variable for your use during your interaction with the current shell
only. Therefore, if you were to use the script command, you would
invoke a new shell; the shell variable you just set would not apply to
this new shell. Also, the next time you login you will be interacting
with a new shell and will have to reset any shell variables you want to
use.
Shell Variables and the .cshrc and .login Files: To set shell variables
so that they are available every time you login, you must add them to
your permanent .login file; to use shell variables every time you
interact with a new shell, add them to your .cshrc (C Shell Runtime
Commands) file .cshrc file. Both of these dot files are located in your
home directory. The default .login and .cshrc files for the UNIX
systems are located in the directory /usr/skel. (See Managing Files on
page 8 for more information on dot files.)
To add command lines to your .cshrc and .login files, use a text editor.
(See Part V for information on the EMACS text editor.) Insert the
command line set shell variable = its value. You can change or delete
the shell variable at any time with a text editor.
The commands you add to these files will activate when you next login.
To invoke the commands in your .cshrc or .login files immediately, use
the source command:
elaine24> source .login Runs the commands in the .login
file. The shell variables are set
as you specified in the .login file.
elaine24> source .cshrc Runs the commands in the .cshrc
file. The shell variables are set
as you specified in the .cshrc file.
Looking at Shell Variable Settings: You can use the set command with no
arguments to see all currently operating shell variables and their
values.
elaine24> set Displays current shell variables and
their values.
argv ()
cwd /student2/tsoi
filec
history 20
Changing the Prompt: The value for the prompt shell variable is what
displays as the shell's prompt. You can customize your shell prompt by
using the procedure shown in the following sample session.
elaine24> set prompt="what now?" Changes the shell prompt from
elaine24> to what now?
what now? Notice quotation marks are used to
enclose more than one word.
To set the prompt automatically for later shell interactions, use a text
editor to change or add the command line set prompt="the desired prompt"
in your .cshrc file.
Setting Your Terminal Type Automatically: The value associated with the
term shell variable is the type of terminal you are using. This shell
variable must ordinarily be set each time you begin a work session,
because programs such as text editors must know what kind of terminal
you're using in order to display information on your terminal screen
properly. You can add the command line set term = your terminal type to
your .login file. (See page 4 for a list of terminal types.)
Setting Your Search Path: One important shell variable is the path
shell variable, which is a list of directories enclosed in parentheses.
This list of directories is your search path; UNIX will search in these
directories for a program that you specify in a command line if you do
not use its absolute or relative pathname. Therefore, if a program is
in your search path, you can type just the name of the program, without
a pathname.
For example, suppose your search path is (/bin /usr/local/X/bin
/usr/bin). When you type a program name or command, the shell looks
first in the /bin directory, second in the directory /usr/local/X/bin,
and third in the directory /usr/bin. It keeps looking until it either
finds the program or command with the specified name or finishes looking
through all the directories in your search path.
elaine24> teachemacs teachemacs begins a tutorial on
EMACS.
teachemacs: command not found. The command is not in the search
path.
elaine24> set path=($path /usr/local/bin) Adds the directory where
teachemacs is located to the
search path.
If you find that you often use a program or command not specified in
your search path, edit or add the command line set path=(the directories
to comprise your search path) in your .cshrc file.
The History Shell Variable: The history shell variable is a number.
This is the number of command lines UNIX will display when you use the
history command. (See Keeping Command History on page 21.) To set the
number of commands that UNIX will save for subsequent sessions, use a
text editor to insert or change the command line set history = number
(of commands to be saved) in your .login file.
Environment Variables: Environment variables are similar to shell
variables, but other programs besides the shell use their values.
Typically, these environment variable names are all uppercase, such as
PRINTER, which determines the default printer. The commands to set,
unset, and look at environment variables are slightly different than
those used with shell variables. Like shell variables, the command
lines can be changed or added to your .login or .cshrc files with a text
editor. environment variables
elaine24> setenv PRINTER sweet0 Sets environment variable PRINTER to
the printer sweet0.
elaine24> unsetenv PRINTER The environment variable PRINTER is
no longer set to sweet0.
Returns to the default printer.
elaine24> printenv Displays environment variables and
HOME=/user/tsoi their values.
SHELL=/bin/csh
TERM=z19
USER=tsoi
About Aliases: Aliases allow you to create shorthand names for
frequently used or lengthy command lines. When the alias appears in the
command line that the shell reads, its text is replaced by the
definition of the alias. Use the alias command to create aliases and
the unalias command to delete aliases.aliases
elaine24> alias sw0 lpr -Psweet0 sw0 will be shorthand for printing
on the sweet0 printer.
elaine24> alias sw0 Shows commands associated with sw0.
lpr -Psweet0
elaine24> alias By itself, alias displays the
ls ls -F aliases you set up.
rm rm -i
sw0 lpr -Psweet0
elaine24> sw0 unix.doc Prints file unix.doc on the sweet0
printer.
elaine24> unalias sw0 Removes the alias sw0.
If you know you want to use the alias in later interactions with the
shell program, you should add the command line to your .cshrc file.
Re-Directing I/O and Building Pipes between Commands
----------------------------------------------------
Input/Output (I/O): Normally, UNIX commands needing user input require
you to type the input at the keyboard. Most UNIX commands show you the
output of the command by displaying it on your terminal screen. The
keyboard is the standard input, and the terminal is the standard output.
But often you might like to store the lengthy output of a command in
another file or cause the input for a command to come from a specific
file. The shell provides a means for redirecting where a command sends
its output or receives its input. The characters <, > and >> are used
to redirect input and output.input and output (I/O)
elaine24> elm rjones < letter Mails the contents of the file
called "letter" to user rjones.
elaine24> who who shows who is logged on to the
system.
tsoi ttyr0 May 17 19:11 (tip-sweetc.stanf)
andrew ttyr1 May 17 19:03 (pinch.stanford.e)
jester ttyr3 May 17 15:32 (tip-cerasa.stanf)
elaine24> who > who.doc Places the output of who command
into the file who.doc. If the file
already exists, its contents are
replaced by the output of the who
command. If the file does not
already exist, it is created.
elaine24> who >> info.doc Appends the output of the command
who to the end of file info.doc.
The contents of this file remain
intact with the output of the who
command attached at the end.
IMPORTANT NOTE
--------------
In the sample session above, the output of who was placed in the file
who.doc. When you re-direct the output of a command to a file that
already exists, the contents of that file will be replaced by the re-
directed output. To avoid accidentally overwriting an existing file
with the > character, use the text editor to put the command set
noclobber in your .cshrc file.
Concatenating Files: By using the cat command, you can string files
together. The cat command displays the files you specify as arguments.
Its standard output appears on the screen of your terminal. But with
the > character, you can re-direct the output from the screen to another
file. Note the warning in the paragraph above.
elaine24> cat pt1.doc pt2.doc > fullbook Concatenates pt1.doc and
pt2.doc into the new file
fullbook.
Pipes: Often it is convenient to make the output of one command become
the input of another command. The UNIX shell provides a means of
connecting the output and input of two commands via a mechanism called a
pipe. The pipe character | is placed between two commands when the
first command's output should be the input of the second.
elaine24> cat pt1.doc pt2.doc | more Concatenates two files
into one, and displays the
new file one screenful at
a time (the command more).
tsoi ttyr0 May 17 19:11 (tip-sweetc.stanf)
andrew ttyr1 May 17 19:03 (pinch.stanford.e)
jester ttyr3 May 17 15:32 (tip-cerasa.stanf)
elaine24> ls | lpr -h Prints (lpr) the contents of the
working directory (ls), suppressing
alpha gamma the header page (-h).
beta omega
More about Characters: The characters in the command line that redirect
input/output (<, >, and >>) and the pipe character (|) are not parts of
the commands themselves. Rather, they are characters that hold special
meaning to the shell. That is, the commands know nothing about the >,
<, and | characters, but the shell recognizes them and provides the
mechanism by which this redirection takes place.
Controlling Jobs
----------------
Foreground and Background Jobs: Because UNIX is multi-tasking, you can
run more than one process or job at a time. If a job is actively
communicating with your terminal, it is running in the foreground. If
you have started other jobs that are still running but not actively
communicating with your terminal, they are in the background.
Normally, when you begin a job by typing a command at the prompt, it
runs in the foreground. If it is lengthy, however, you may want to keep
your terminal free so you can work on something else while the first job
is underway. To begin a job in the background instead of the
foreground, type the & character at the end of the command line:
elaine24> sort bigfile > big.out & sort alphabetizes the contents
bigfile. Places the output
[1] 9254 into big.out. The & character
specifies the job should take
elaine24> place in the background.
In this sample session, the [1] is the job number, and 9254 is the
process identifier (PID) for that job. Notice the prompt immediately
returns. When the job is finished, the system displays a message that
tells you it has finished executing your command. (To receive immediate
notification, place the shell command set notify in your .cshrc file.)
A Note About AFS: Many Leland Systems accounts (including all Power and
Wisdom accounts) are AFS-based UNIX accounts (as opposed to NFS-based
accounts). (If the pwd command says your home directory is in /afs/ir,
you have an AFS account.) AFS is a method by which different computers
may share the same files, conserving disk space and making a wider
variety of computers available to each user. Because of the increased
file security offered by AFS, extremely long login sessions and
extremely long-running background jobs (longer than 25 hours) may be
problematic. For information on how to successfully run programs
requiring more than 25 hours of real time, contact a consultant at 725-
2101 or send electronic mail to consult@leland.
Finding Out What Jobs Are Running: You can check on the status of your
jobs by using the jobs or the ps command:
elaine24> spell intro.doc > misspell & The character & specifies
that this spell job should
take place in the background.
[1] 9244 Its job number is [1] and the
process identifier is 9244.
elaine24> ls /usr/bin > binlist & This ls job will also take
place in the background. Its
[2] 9300 job number is [2] and the
process identifier is 9300.
elaine24> who | more Displays who's using the system, by
screenful.
^Z ^Z indicates you stopped the job
with C-z.
Stopped
elaine24> jobs jobs shows status of jobs, by job
number.
[1] - running spell intro.doc > misspell Jobs 1 and 2 are
running; job 3 is
stopped.
[2] running ls /usr/bin > binlist
[3] + stopped who | more
elaine24> ps ps shows status of jobs, by process
identifier (PID). STAT is
PID TT STAT TIME COMMAND job status: R=running, S=sleeping,
T=stopped.
6964 p4 S 0:03 -csh (csh) This is your original shell.
7824 p4 R 0:00 ps ps is the command running in the
foreground.
7213 p4 R 0:01 spell spell is a command running in the
background.
7345 p4 R 0:02 ls ls command is also running in the
background.
5233 p4 T 0:00 who The who command stopped; note the
T under STAT.
5235 p4 T 0:00 more The more command that was part of
the who command also stopped. For
more information on what these
fields mean, issue the command man
ps.
Stopping a Background Job: To stop a job running in the background, use
the stop command. You can use the bg command to continue the stopped
job. If you still have stopped jobs when you log out, a message will
provide a reminder. Although it is not recommended, you can choose to
ignore the message and type logout again. Instead, you should use the
jobs command to review the suspended jobs and then either use the bg
command to continue them or the kill command to eliminate them
altogether.
Continuing and Moving Jobs: The command bg with no arguments continues
the most recently stopped background job where it left off. If you want
to continue a specific job you can type bg %job number. For example, to
continue job number 5, type bg %5. The command fg moves a job running
in the background to the foreground. To move job number 5, you would
type fg %5.
elaine24> bg The command bg resumes the job.
It now continues in the background.
[1] ls /student1 > studentlist & The number for this job is [1].
elaine24> jobs The jobs command shows job 1 is
running.
[1] Running ls /student1 > studentlist
elaine24> fg %1 The fg command brings a job
currently running in the
ls /student1 > studentlist background to the foreground. You
specify which job with the %
character and the job number.
Killing a Background Job: To stop a job running in the background when
you are sure you don't want to finish it later, use the kill command.
You cannot resume any job that you have killed. Specify the job to stop
or kill by either its job number or its process identifier (PID). A
message appears stating that the job has been killed or terminated. If
it does not appear, repeat the kill command or type kill -9 (an emphatic
kill).
elaine24> sort bigfile > big.out & The & character specifies that
this sort job should take place
[1] 7983 in the background. Note job
number and PID.
elaine24> ls /student1 > studentlist & This ls job will also take
place in the background. Note
job number and PID.
[2] 9254
elaine24> stop %1 Stops the process running with job
number 1.
[1] + Stopped (signal) sort bigfile > big.out
elaine24> kill 9254 Kills the process running with PID
9254.
[2] Terminated ls student1 > studentlist The message confirms it
has been terminated.
elaine24> kill -9 %1 Kills the process running with the
job number 1.
This is an emphatic kill.
Keeping Command History
Reviewing Your Commands: The shell has a mechanism that allows you to
review the commands you entered most recently. The number of commands
you can review is determined by the value of the history shell variable.
You can then use a variety of commands to review and repeat your saved
commands:
elaine24> set history = 10 Sets the number of commands for UNIX
to save at n (10 here).
elaine24> history Displays the previous 10 commands,
as set in the step above.
11 emacs .alias
12 who
13 finger statman
:
19 cat todolist
20 history
elaine24> !! Re-executes the immediately
history preceding command.
12 who
13 ...
:
20 history
21 history
elaine24> !cat Repeats most recent command starting
with string cat in the previous 10
cat todolist commands (as set above).
*** don't forget lunch appointment tomorrow!
elaine24> !13 Repeats command 13 if it is in the
previous 10 commands.
finger statman
:
Saving Your Commands and the Shell's Responses: Sometimes you may want
to save your commands and the shell's responses in a file. That way,
you can see or print the information later. You may want to record the
running of a specific program and inspect this session later, at your
leisure. The script command saves the record of your interaction with
the shell in a file named typescript in the working directory. You can
specify different file names if desired by typing script filename; type
man script at the shell prompt for more information. To signal the end
of the recording, type the command exit. At that point, you can look at
the typescript file by typing more typescript at the prompt.
elaine24> script Saves all commands and shell
responses that follow.
Script started, script is typescript
csh> testprog
What is the result of 3+4? 7
Correct!
csh> exit Ends the recording.
csh> Script done, file is typescript
elaine24> more typescript Displays the commands and shell
responses just saved.
Script started on Tue May 17 23:06:57 1988
csh> testprog
What is the result of 3+4? 7
Correct!
csh> exit
script done on Tue May 17 23:07:30 1988
Part V: Using EMACS
===================
About Part V: EMACS is a text editing program available on the Leland
Systems;. Part V is an introduction to EMACS, explaining how to use the
program. For a more complete list of EMACS commands and functions,
refer to the EMACS Reference Card.
Most EMACS commands are executed with CONTROL (C-) and ESCAPE (ESC)
command sequences. Refer to Command Sequences on page 3 for more
information.
Entering EMACS: To enter the text editing program and create a new text
file, type the command emacs at the system prompt. If you want to edit
a file that already exists, include its name (with the relative or
absolute pathname, if necessary) as the argument to the emacs command.
elaine24> emacs unix.doc
Upon startup, the editor copies the contents of the file specified in
the argument into an internal buffer, or work space. If you didn't
specify a file, the editor creates a new, blank buffer. During the
editing session, you make changes to this buffer and not to the contents
of the original file. The original file remains unchanged until you
explicitly tell the editor to write over the old file with the contents
of the edit buffer. Therefore, if you quit an editing session without
saving your changes, the file you worked on remains as it was before you
began the editing session.
Moving in the Text: The cursor indicates your position within the text
of the buffer. There are two ways to move the cursor. On Macintosh
machines, and on some PCs and workstations, you can use the arrow keys
near the number pad. If that doesn't work, or if that option isn't
available, use the following movement command sequences:
Backward Forward
C-b C-f One character
ESC b ESC f One word
C-p C-n One line
C-v ESC v One screen
C-a C-e Beginning (or end) of line
ESC a ESC e One sentence
ESC < ESC > Beginning (or end) of buffer
To re-display text, with the line where the cursor is currently located
positioned in the center of the screen, type C-l. To cancel a partially
typed or accidental command, type C-g.
Editing Text: Any editing that you do will affect the character
immediately at or preceding the location of the cursor. To insert text,
move the cursor one position beyond where you want the new text to go,
and type as normal. Delete a character with the DELETE key. Please
note that EMACS does not wrap text down to the next line. Therefore,
you must press the RETURN key at the end of each physical line, before
you get to the right margin.
Saving Your Work: You should save your work periodically during an edit
session to backup your changes. Frequent saving minimizes loss of data
should the computer system crash. To save any changes you have made in
the buffer, type C-x, then s. This writes the contents of the buffer
over the original file. To save the contents of the buffer to a new
file, type C-x, then C-w. The editor then prompts you for a file name
for the saved buffer.
Note: The normal save command sequence may cause some modem programs to
freeze. If this is the case, type C-q to unfreeze the modem, then use
the C-x C-w command sequence and save the file with the same name.
Leaving EMACS: To stop EMACS temporarily, type C-z. Remember to save
your work first. When you issue the command fg %job number at the
system prompt, the editor resumes where you left off. For more
information, see Controlling Jobs on page 19.
To end an EMACS editing session, type C-x, then C-c. Remember to save
your changes before exiting. If you have modified the text in a buffer
and attempt to exit without saving your changes, the editor asks you if
want to save the changes.
For More Information: Consult the document already mentioned, EMACS
Reference Card. There is also an online tutorial for EMACS, which
provides a complete interactive introduction. Type teachemacs at the
system prompt to start the tutorial. For more detailed information on
the EMACS editor, you may want to attend an introductory class on EMACS.
These classes are offered at the beginning of Autumn, Winter and Spring
Quarters; class schedules are available for the first few weeks of each
quarter in the document racks on the second floor of Sweet Hall. If you
have further questions about EMACS, contact a consultant at 725-2101,
consult@leland.
Part VI: Printing
=================
About Part VI: You can print files or other text (e.g., output of
commands) at any of the printers in Sweet Hall or in the Meyer and
Tresidder Computer Clusters. (In some clusters, you will have to set up
a printing account to have printing capabilities.) Each printer has a
print queue, which contains the print jobs that are waiting to be
printed, lined up in the order in which they arrive at the printer.
Print Commands: As shown in the following examples, the print commands
lpr, lpq and lprm are used to send a print job to a particular printer,
display the print queue and remove a request from a print queue. A
useful argument for these commands is the -Pname, where name is the
printer you wish to use. A useful option is -h, which suppresses the
header page to your print job, printing only the specified file and
saving one piece of paper. Each UNIX system has a default printer; all
print jobs initiated from that system will print at the default printer,
unless you specify otherwise in the argument.
elaine24> lpr -h SOC22 Prints the file SOC22 on the default
printer without the header page.
elaine24> lpr -Psweet0 SOC22 Prints the file SOC22 on the printer
named sweet0.
elaine24> ls | lpr -h -Psweet0 Prints the output of the command ls
on the printer sweet0.
elaine24> lpq -Psweet0 Displays print queue of the sweet0
printer.
lp is ready and printing via dev
Rank Owner Job Files Total Size
1st ksteele 105 SOC22 55706 bytes
2nd ksteele 106 (standard input) 70 bytes
elaine24> lprm 106 Removes job 106 from the default
print queue.
This only works if the job hasn't
already been processed by the
computer managing the queue.
If you are working on a UNIX workstation on the second floor of Sweet
Hall, you can use the printers sweet0, sweet1, sweet2 (the default
printer), sweet3, sweet4 and sweet5. Sweet0 is a high-speed line
printer. The rest are laser printers and are capable of handling files
in PostScript format.
For more information on the print commands and their options, consult
the online UNIX manual by typing man command.
Formatting a Print Command: The enscript command allows you to format a
print job as you send it to the printer. When you use enscript, your
files are printed with headers, and two pages of material are compressed
to fit on one page, saving paper. Type man enscript at the system
prompt to consult the online UNIX manual for arguments that you can use
to format the output for a particular printer.
elaine24> enscript unix.doc -2r -G -h Prints unix.doc with 2 columns
(-2) and rotates the page (r)
so that the columns are wider.
-G adds a header to the top of
each page, and -h suppresses
the header page.
Note: The enscript command does not work for printing PostScript files.
Type man postscript for information on printing PostScript files.
Changing the Default Printer There are times when you may want to
change the default printer to another printer. For example, the normal
default printer may be down, or perhaps an application you're using only
works with a specific printer. To change the default printer, reset the
environment variables PRINTER to the name of the printer that you want
to use. This changes the default printer until you log out. For more
information, see Environment Variables on page 17.
elaine24> setenv PRINTER sweet2 Designates the printer sweet2 as the
default printer
Part VII: Staying Informed about System Activity
================================================
About Part VII: You can obtain information about a UNIX system's
status, changes made to the system, and a particular computer's recent
activity. You can find out which other users are currently logged in,
and what a particular user is doing.
System Messages: When you first log on to the Leland Systemss;, there
may be either a new system messages or information regarding an old one.
These messages are sent by the system administrators to inform users
about changes in the systems or in their accounts, and may instruct
users to change their passwords and/or a file in their home directories.
Finding Out About a Particular Computer: The uptime command displays
information regarding the status of the computer you are working on:
the time, how long the machine has been up and
running, the number of users currently logged on, and the load average.
As more users log on to the system and do work, the load average
increases. This gives you a rough idea of how busy the system is.
elaine24> uptime
12:10pm up 1 day, 16:35, 2 users, load average: 1.34, 1.28, 1.66
The who command displays who is currently logged in to the computer you
are on. From left to right, the first entry is the user's login name,
followed by that person's terminal (tty) and the date, time, and
location of the login.
elaine24> who
tsoi ttyp0 May 17 19:11 (109.83.1.130)
ksteele ttyp1 May 17 19:03 (ksteele-macII)
jester ttyp3 May 17 15:32 (jewel)
The command who am i displays that line of information only for the user
who is logged on to that terminal. This is useful in finding who is
logged on to an unattended computer or workstation. The w command is
similar to who; it lists all the users on the system and what they are
doing.
Finding Out About a Particular User: To find out more information about
particular users, use the finger command. When you use finger with no
arguments, you get abbreviated information (full name, tty, idle time,
login time, office) for each user on the computer you are using. When
you use the command finger with a username and a host as the argument,
information on that user, including her .project and .plan files
display.
elaine24> finger ksteele@cardinal
Login name: ksteele In real life: Kate Steele
Directory: /s16/k/ksteele Shell: /bin/tcsh
On since Jan 13 11:46:57 on ttyp3 from ksteele-macII
New mail received Wed Jan 13 13:08:06 1993;
unread since Wed Jan 13 11:11:03 1993
Project: Finishing the UNIX documentation.
Plan: I'd like to teach the world to sing...
Please note that, due to system backups, the information about when a
user last logged in and/or read mail may be inaccurate.
Use a text editor to add messages or information to the .project and
.plan files in your home directory. See Managing Files on page 8 for
more information on dot files. These files should only contain
information that you would like other users to know about you. Also, be
sure that you give permission for others to read your .project and .plan
files. If you don't, people who finger your username won't be able to
see the information you include in those files.
To get more information on an individual user, or to find out who a user
is, use the whois command. When you type whois user@host, you get a
user's actual name, e-mail username, Stanford affiliation, phone, fax
and office numbers, and other information.
Appendix A: UNIX Command Summary
================================
Appendix A lists the UNIX commands that appear throughout this document.
The first column lists the topic, the second lists the command, the
third contains a short definition for each command, and the last column
lists the page number on which the command first appears. All
information in italics is variable input and should be replaced with
specific information, such as a file or directory name.
This information is meant primarily as a reference supplement for this
document. There is a reference card, also called UNIX Command Summary,
that contains most of this information and can be used separately. As
stated earlier in this document, there is also an online UNIX reference
manual. See Getting Help below.
Beginning and Ending Work Sessions
----------------------------------
login Begins login process on the computer you want
to use.
set term=term type Tells UNIX system what kind of terminal you're
using.
password Allows you to change your password.
logout Logs you off the computer you've been using.
Getting Help
------------
help Accesses the online help files for various UNIX
commands.
help docs Accesses online documents about the Leland
Systems.
man man Displays information about the online UNIX
manual.
man command Consults online UNIX manual section about
command.
man -k keyword Lists all commands associated with keyword.
learn Starts UNIX tutorial program.
Managing Directories
--------------------
pwd Prints your working directory.
mkdir dir Creates a new subdirectory called dir.
cd Changes to your home directory.
cd .. Changes to directory one level above.
cd dir Changes to dir (use either the absolute or
relative pathname).
rmdir dir Removes subdirectory dir (must be empty).
ls Lists contents of working directory.
Managing Files
--------------
more file Displays contents of file, screen by screen.
head file Displays the first 10 lines of file.
tail file Displays the last 10 lines of file.
mv file1 file2 Moves or renames file1.
cp file1 file2 Makes a copy of file1, and names it file2.
rm file1 Permanently removes file1.
cat file1 file2 > file3 Concatenates file1 and file2 into new
file3.
Transferring Files
------------------
ftp host Starts file transfer program between your
machine and host.
get file Receives a copy of file from the remote
computer.
send file Sends a copy of file to the remote computer.
quit Ends file transfer program.
Security Changes
----------------
ls -l Lists contents of working directory with
security information.
chmod useracc name Changes type of access (acc) of user group
for a particular file or directory (name).
fs listacl name AFS only: shows access rights for a file or
directory (name).
fs setacl name user acc AFS only: changes type of access (acc) of
user for a particular file or directory
(name).
Re-directing I/O
----------------
<, > Redirects input and output in command lines.
command >> file Appends output of command to the contents of
file.
command1 | command2 Uses output of command1 as input of
command2.
Shell-related
-------------
exit Quits from current shell.
source .cshrc Runs commands in .cshrc file.
source .login Runs commands in .login file.
set variable=setting Sets the specified shell variable to
setting for this work session. Some
common shell variables are path, prompt,
history and term.
echo $variable Displays the setting for variable.
unset $variable Removes the setting for variable.
setenv VARIABLE Sets environmental VARIABLE to setting for this
setting work session.
printenv Displays environmental variables and their
settings.
unsetenv VARIABLE Removes setting for VARIABLE.
alias name command Allows you to refer to the command line
command with the shorter term name.
alias Displays the aliases you have set up.
unalias name Removes name from active aliases.
Controlling Jobs
----------------
jobs Shows status of currently running jobs by job
number.
ps Shows status of currently running jobs by
process identifier.
command & Specifies that the job started by command run
in the background.
stop $job# Temporarily stops specified job.
bg %job# Resumes specified job in background.
fg %job# Brings specified job from background to
foreground.
kill $job# Permanently stops specified job.
history Displays last ten commands used.
!command# Re-executes specified command.
script Saves the following interaction with the shell
to a file so it can be viewed again later.
EMACS
-----
emacs Begins a new text document.
emacs file Places the contents of file in a buffer for
text editing.
teachemacs Starts EMACS tutorial.
C-x s Saves changes to the file.
C-x C-w Saves changes to a new file.
C-z Stops EMACS temporarily.
C-x C-c Quits EMACS.
Printing
--------
lpr file Prints file at default printer
lpr -h file Prints file at default printer, suppressing the
header page.
lpr -Pprinter file Prints file at printer.
lpq Displays print queue of default printer
lprm job# Removes specified print job from print queue.
enscript -2r -G -h file Adds heading information to each page of
file and prints two columns per page;
suppresses header page.
System Activity
---------------
uptime Displays status of computer you are working on.
who Displays information on other users logged on
to the same computer.
who am i Displays information on user logged in at
specific computer or workstation.
finger user Displays information about user.
whois user@host Displays information about user.
Miscellaneous
-------------
(These commands are not explained in this document.)
sort file Sort each line of file alpha-numerically.
spell file Conducts a spell check on contents of file.
date Displays the date and time.
fs listquota AFS only: displays disk quota and usage.
quota -v Non-AFS only: displays disk quota and usage.
telnet host Allows you to connect to remote computer host.
grep "string" file Displays all lines in file that contain the
words string (in quotation marks).
Appendix B: Using Compilers-A Quick Guide
=========================================
About Appendix B: This appendix provides a brief introduction to
compiling, covering the C, Pascal and FORTRAN languages. Other
languages are compiled similarly. This appendix assumes that you know
how to use the language you are working with. It also assumes that you
know how to use a text editor such as EMACS. To see a list of compilers
available on the Leland Systems;, type the command man -k compiler.
A compiler produces a machine language program from the source program
that you create. Using UNIX, it translates the source program into the
basic language of the computer; programs written in machine language
require no further interpretation by the computer.
Compiling Procedures: This section uses the C language in its examples.
(The C programming language is closely related to UNIX; most of the UNIX
operating system and its commands are written in C.) These procedures
are basically the same for Pascal and FORTRAN-only the extensions and
the names of the compilers change, as described in the following
sections.
1. Use a text editor to create one or more files containing the source
program. You must write the source program in a development
language. Each file containing the source program should end with an
extension, specifying which language is used (e.g., .c for C).
2. After creating the source program, invoke the compiler for that
language. The compiling command takes as its argument the name of
the file(s) containing the source program. (For more information on
the C compiler, use the command man cc.)
elaine24> cc main.c Compiles from the file main.c.
If the system prompt returns, the compiler has successfully converted
the source program into a machine executable program, i.e., a program
that you can run. Unless you specify otherwise, the name of this
program is a.out. To run this program, simply type its file name:
elaine24> a.out Runs the new program.
elaine24> cc -o myprog main.c Allows you to specify the name of the
executable file or program (instead
of a.out, it will be myprog).
If the program doesn't run as expected, i.e., the program 'bombs' or the
results aren't what you expect, use a de-bugging program such as dbx to
diagnose the problem. (For more information on dbx, type man dbx.)
Once you've isolated the problem, use a text editor to correct the
error.
If the compiler cannot compile the file(s), error messages display on
the screen. If you are compiling a single file, the message tells you
which lines contain errors. If you are compiling multiple files, the
message tells you which lines within which files contain errors. Use a
text editor to correct the errors.
To check individual files before compiling multiple files, follow these
steps:
elaine24> cc -c main.c Compiles the file main.c, creating an
intermediate file main.o, which can be used
later to create the executable file or program.
This is useful when you have edited a file and
want to check to make sure it will compile
successfully before you compile it with the
other files comprising your program.
elaine24> cc -o myprog main.o display.c Creates executable file or
program from files main.o
and display.c.
Compiling with Pascal: The name of each file containing the source
program should end with the extension .p, such as main.p. The Pascal
compiler is called pc. Compiling procedures are the same as those for
C. (For more information on the Pascal compiler, use the command man
pc.)
Compiling with FORTRAN: The name of each file containing the source
program should end with the extension .f, such as main.f. The FORTRAN
compiler is f77. Compiling procedures are the same as those for C.
(For more information on the FORTRAN compiler, use the command man f77.)
Using Libraries While Compiling: You can include a library in your
program, in addition to the standard input/output library, in order to
use their pre-existing subroutines. It is very important that you place
the -l option after the name of your source file(s) on the command line.
Otherwise, the external library routines may not be correctly linked to
your program. The following example uses a C library:
elaine24> cc main.c -lm The l option indicates you are calling up a
library. The m here stands for the math
library, which includes functions for
calculating sine, cosine, and other useful
mathematical functions.
Some of the Leland Systems have FORTRAN libraries like IMSL and NAG
installed. To use subroutines from those libraries in your own FORTRAN
programs, use these commands:
elaine24> f77 main.f -limsl Uses the IMSL library.
elaine24> f77 main.f -lnag Uses the NAG library.
Last modified Thursday, 19-Jan-2006 11:26:32 AM
