Linux Quick Command Reference
This content is not in any particular order. This is just a short synopsis of
what you would see, if you skimmed through the book.
Common UNIX filename Extensions
Extension Description
.a Archived file or assembler code.
.au Audio file
.c C language source file
.csh C shell script
.enc Encrypted file
.F FORTRAN source code before
processing
.gif Graphics Interchange format file
.gl Animation file
.gz File compressed with gzip
.h C program header file
.jpg or jpeg Joint Photographic Experts Group
format
Alphabetical Unix Command List:
addbib - create or extend a bibliographic database
apropos - locate commands by keyword lookup
ar - create library archives, and add or extract files
at - execute a command or script at a specified time
awk - pattern scanning and processing language
banner - display a string in large letters
basename - display portions of path names and filenames
batch - runs jobs when the system load level permits
biff - give notice of incoming mail messages
cal - display a calendar
calendar - a simple reminder service
cancel - cancel requests to a printer
cat - concatenate and display
cb - a simple C program beautifier
cc - C compiler
cd - change working directory
checknr - check nroff and troff input files; report possible
errors
checkeq - checks documents formatted with memoranda macros
chgrp - change the group ownership of a file
chmod - change the permissions mode of a file
clear - clear the terminal screen
cmp - perform a byte-by-byte comparison of two files
colcrt - filter nroff output for a terminal without overstrike
capability
comm - selects or rejects lines common to two sorted
files
compress - compress files (see uncompress also)
cp - copy files
cpio - copy file archives in and out
cpp - the C language preprocessor
csh - a shell with a C-like syntax and advanced
interactive features
ctags - create a tags file for use with ex and vi
cut - Writes selected bytes, characters, or fields from
each line of a file.
Linux Glossary
CORBA (Common Object Request Broker Architecture)
A specification developed by the Object Management
Group detailing how object messaging are handled
across different platforms.
core dump Main memory content that is produced when
a program does not operate successfully. You can use
this information to find out where the failure
occurred.
cron An utility used to schedule processes. System file
backups and machine maintenance routines are often
scheduled by cron.
crontab A system utility that enters cron jobs
information into a formatted file. The crontab
file is checked periodically to see if a scheduled
process should start.
current directory The directory that a UNIX user is
in now ,also called the present working directory
symbolized by the (dot) . notation and displayed by
using the pwd command.
cursor An indicator used to show the current position
on screen. Normally this is a blinking vertical or
horizontal symbol.
daemon Pronounced "day-mon," or "de - mon."
daemon is an automated process (sometimes spelled
or pronounced as "demon") that performs a standard
routine or service. For example, an e-mail program that
sends an automated message whenever it receives an
e-mail message.
Common UNIX Daemon
Daemon Descriptions
ftpd File transfer protocol daemon
inetd Internet daemon
lockd Network lock daemon
lpd Line Printer daemon
named Internet domain name server daemon
nfsd NFS daemon
pppd Point-to-point protocol daemon
uucpd UUCP daemon
DARPA (Defense Advanced Research Projects Agency)
A military agency that developed the ARPANET.You can
think of this as the original Internet.
data gram A packet that contains data and addressing
information. Data grams are self-contained and carry
a complete address.
debugger A program that shows the logic path and
values of registers and variables during execution
of a process to locate where a failure occurred. Unix
has a debugger named sdb that is used to locate
instructions that were executed during a core dump.
default user environment The environment that is set
up for new users who are added to a system by the
useradd command, if installed.
default value The value used by a program for an
argument or variable when the user does not specify
a value.
fdev The directory that contains the filenames used
to gain access hardware drivers for, printers, terminals
and other devices.
device Peripheral equipment used in input or output
(I/O) of data. Unix separates processes from the I/O
devices to allow flexibility. Device files and names
are stored in the /dev directory.
device driver Allows data to transmit among
computers and their peripheral devices.
device independence The ability of a program to accept
input and output with any peripheral hardware.
Idevinull A special destination file for output or
input, used when output is not desired, or as an input
when nothing is to be read in. A type of "throw away"
trash bin file.
directory A directory is a holding area for files or
other directories. You can access files by
supplying all the directory names from the root
down to the directory holding the file. This is called
the full path name.
distributed database system A database system that
appears as a single database to end users, even
though the data physically resides on more than one
machine.
distributed file system A file system in which user
programs and data files are physically distributed
over several computers on a network, but can be used
by any user who has access to any of the files as if
they were local files.
D.1.1 Games
This section lists packages that contain a variety of games.
cxhextris -- (Version 1.0, 39K)
CXHextris is a color version of the popular xhextris game,
which is a Tetris-like game that uses hexagon shapes instead of
square shapes. CXHextris runs within the X Window System.
Install cxhextris if you enjoy playing Tetris or Tetris-like games
and you'd like to play one on your system. You'll need to have
X installed in order to play CXHextris.
fortune-mod -- (Version 1.0, 2,342K)
Fortune-mod contains the ever-popular fortune program. Want a
little bit of random wisdom revealed to you when you log in?
Fortune's your program. Fun-loving system administrators can add
fortune to users' .login files, so that the users get their dose
of wisdom each time they log in.
Install fortune if you want a program which will bestow these
random bits o' wit.
gnome-games -- (Version 1.0.2, 3,342K)
[W]
GNOME is the GNU Network Object Model Environment. That's a fancy
name, but really GNOME is a nice GUI desktop environment. Its
powerful, friendly and easy-to-configure interface makes using
your computer easy.
This package installs some GNOME games on your system, such as
gnothello, solitaire, tetris and others.
gnuchess -- (Version 4.0.pl79, 1,428K)
The gnuchess package contains the GNU chess program. By default,
GNUchess uses a curses text-based interface. Alternatively, GNUchess
can be used in conjunction with the xboard user interface and the
X Window System for a graphical chessboard.
You should install the gnuchess package if you would like to play
chess on your computer. You'll also need to install the curses
package. If you'd like to use a graphical interface with GNUchess,
you'll also need to install the xboard package and the X Window
System.
kdegames -- (Version 1.1.1pre2, 4,962K)
Games for the K Desktop Environment. Included with this package are:
kabalone, kasteroids, kblackbox,kmahjongg, kmines, konquest, kpat,
kpoker, kreversi, ksame, kshisen, ksokoban, ksmiletris, ksnake,
ksirtet.
D.1.2 Graphics
This section lists packages that provide graphics that are fun to
look at.
xdaliclock -- (Version 2.14, 80K)
The xdaliclock program displays a digital clock, with digits that merge
into the new digits as the time changes. Xdaliclock can display the time
in 12 or 24 hour modes and can will display the date if you hold your
mouse button down over it. Xdaliclock has two large fonts built in, but
is capable of animating other fonts.
xloadimage -- (Version 4.1, 255K)
The xloadimage utility displays images in an X Window System window,
loads images into the root window, or writes images into a file.
Xloadimage supports many images types (GIF, TIFF, JPEG, XPM, XBM,
etc.).
Install the xloadimage package if you need a utility for displaying
images or loading images into the root window.
xlockmore -- (Version 4.13, 759K)
The xlockmore utility is an enhanced version of the standard xlock
program, which allows you to lock an X session so that other users
can't access it. Xlockmore runs a provided screensaver until you
type in your password.
Install the xlockmore package if you need a locking program to secure
X sessions.
postgresql -- (Version 6.4.2, 6,918K)
[S]
Postgresql includes the programs needed to create and run a PostgreSQL
server, which will in turn allow you to create and maintain PostgreSQL
databases. PostgreSQL is an advanced Object-Relational database
management system (DBMS) that supports almost all SQL constructs
(including transactions, subselects and user-defined types and
functions).
You should install postgresql if you want to create and maintain your
own PostgreSQL databases and/or your own
PostgreSQL server. If you are installing postgresql, you should also
install postgresql-data, which will help you get started with
PostgreSQL.
postgresql-clients -- (Version 6.4.2, 938K)
[S]
Postgresql-clients includes the client programs and client libraries
that you'll need to access a PostgreSQL database management system
server. This package contains the client libraries for C, C++ and
PERL, as well as command-line utilities for managing PostgreSQL
databases on a remote server. If you just want to connect to an
existing remote PostgreSQL server, this package is all you need.
You should install postgresql-clients if you're installing postgresql.
You should also install postgresql-clients if you're not installing
postgresql, but you want to access PostgreSQL databases on a remote
PostgreSQL server.
wget -- (Version 1.5.3, 335K)
GNU Wget is a file retrieval utility which can use either the HTTP or
FTP protocols. Wget features include the ability to work in the
background while you're logged out, recursive retrieval of directories,
file name wildcard matching, remote file timestamp storage and
comparison, use of Rest with FTP servers and Range with HTTP
servers to retrieve files over slow or unstable connections,
support for Proxy servers, and configurability.
Install wget if you need to retrieve large numbers of files with
HTTP or FTP, or if you need a utility for mirroring web sites or
FTP directories.
xchat -- (Version 0.9.4, 196K)
[W]
X-Chat is yet another IRC client for the X Window System, using the
Gtk+ toolkit. It is pretty easy to use compared to the other Gtk+ IRC
clients and the interface is quite nicely designed.
alias
Alias lets you define new commands, by inventing a
new name for script programs or commands.
Here are three reasons for using an alias:
Reduces the amount of typing that you
do. If you are already using a command with
the same options, you can create a one-character
alias and use that instead.
Automate complex difficult to remember
command procedures.
To avoid lengthy path searches. Commands
start quicker when aliased to the complete
path name.
The syntax you use for this command depends on
which shell you use.
The Korn shell syntax is:
alais [options] [name] [= command]]
which assigns a shorthand name to command. If you
leave out the [= command ]],you can print the alias
for name. If you leave out name you can print all
the aliases. There are two options for alias in the
Korn shell. If you use the less command with the -alt
options in the Korn shell you can alias this to a
single letter by typing:
alias l = ls -alt
Now,just type l if you want to see a long
directory listing showing all files sorted by the
time they were last modified.
Options Descriptions
-t Makes the Korn shell remember the
full path name for the aliased
command,which allows it to be
found quickly.You can then issue -t
from any directory.Tracked aliases
are the same as hashed commands in
the Bourne shell.
Options Descriptions
-x Exports the alais so that you can
use it in shell scripts.
alias
C Shell Syntax
The syntax for alias in the C shell is:
alias [name] [command]
where name is the sorthand name or alias you want
to use with command. Just like the Korn shell, if
you leave out [command], alias prints the alias for
name and if you leave out name, alias prints all the
current aliases. In the C shell, you can define an
alias on the command line, but aliases are
stored in .cshrc so that they are available as
soon as you log in. To bypass the alias ,use the
original command name, by typing \name.
at
The at command takes a list of commands and runs
them at the time you specify; it is not necessary
for you to login to the system at the time the
command is scheduled to run. at allows you to run
jobs unattended when the system load is low. This
procedure is usually started after normal working
hours.
The Syntax for at are:
at options 1 time [date] [+increment] commands
at options 2 [ jobs ]
You can use two sets of options with at: options 1
controls setting the time and date. options2 lets
you make changes to scheduled jobs.
In options1,you type the information needed by at,
followed by the command you want to run and then
end the sequence by typing Ctrl-D on the
following line.
You can enter the commands from the
keyboard, pipe them in from another program or use
input redirection to use an existing file of commands.
at returns a job ID when it is started. You use
this ID number with the second syntax showed above.
Many systems restrict the use of at. Only
users specified in the file /usr/lib/cron/at. allow
can schedule jobs; if this file doesn't exist, the file
/usr/lib/cron/at.deny holds a list of users who cannot
use at. If either file does not exist, only the super
user can use at.
When UNIX executes commands using at, it uses e-mail
to send you output from this process; you can redirect
this mail if you want to.
Options and Arguments
In the first line of syntax, time is the time of day
when you want at to run your job. You can specify
time in one of several different ways:
A one or two-digit number specifying the hour.
A four-digit number specifying the hour and
minute.
Two numbers separated by a colon to specify
hours and minutes.
noon, midnight or now.
Be sure to note whether the time is am, pm or Zulu
(for Greenwich mean time) to specify the precise time.
You can specify the date you want to use as:
A three-letter month name followed by the day
number, an optional comma and an optional year
number.
A day of the week, abbreviated to the first
three letters.
today or tomorrow.
If you omit date, at defaults to today if the hour
specified in time is later than the current time; if not,
at runs the job at the same time tomorrow.
The final argument,increment,is a positive number
followed by minutes,hours,days,weeks,months,or years
or their singular form.at adds this increment to the
time and date specified. In place of increment,you
can use the word next to specify next week or next
year.
In the second line of syntax showed above, jobs is a
list of one or more at job numbers.
You can use the options shown to report or remove
jobs.SCO adds one more option,q letter,which places
a job in the queue specified by letter. Three letters
have a special significance:
a (the default) represents the at queue, b the batch
queue and c, the cron queue.
Options to Use with at:
Option Description
OPTIONS1
-f filename Executes the commands contained in
filename.
-m Sends mail, if any to the user when
the job is complete.
OPTIONS2
-l [jobs] Reports all jobs, or if jobs is
specified, reports on them.
-r [jobs] Removes jobs. You must be the
owner of the job or the superuser.
For instance:
To run the spell program on a file called bigfile at
four a.m. tomorrow and send any output to a file called
wordout,use:
at 04 tomorrowspell bigfile > wordout(CtrlD)
job 424765800.a at Tues Oct 30 04:00:00 2000
The last line above contains the job number and the
time at will run the job.
See also Batch
du
du tells you the amount of disk space used by a
particular directory and it's sub directories; it
lists the diskspace in 512 byte blocks. Incomplete
blocks are rounded up.
The syntax for du is:
du [options] [directories]
If directories are not found, the du command will
show you the disk space of the current directory
and all of its sub directories and files.
Options Descriptions
-a Shows the totals for all files and
sub directories.
-f Shows totals for files and directories
in the current file system only.
-k Gives totals in kilobytes.
-L All symbolic links are followed.
-P Symbolic links are not followed.
-r Displays a message cannot open.
-s Prints to screen a sum total for each
filename and directory name.
-u Ignores files with more than one link.
-x Prints to screen totals for file and
directories in the current file system
only.
Examples:
To check out the free space in your home directory
for instance, type:
du / home / patrick
You should see:
1100 / home / patrick / games
23545 / home / patrick / assembly
324746 / home / patrick / xfiles
echo
echo writes arguments to the standard output, which
is usually a terminal. echo is also a command in the
C and Bourne shell.
The syntax for echo is:
echo [-n] [string]
echo is useful in shell scripts by prompting
you for input or give the status of a process.
echo
Options and Arguments
The -n option turns the newline off. Put your message
inside string and surround your message in quotes.
echo sequences
Sequence Descriptions
\b Backspace
\c Suppress final newline
(same as - n option)
\f Formfeed
\n Newline
\r Carriage return
\t Tab
\v Vertical tab
\\ Backslash
\0n Octal number, specified by n
Examples
This shell script prints-to-screen a message:
echo " X Files are running on node 1 ! "
If you run the shell script you should see:
X Files are running on node 1 !
KnowledgeWorks, Inc
364 Green Street
P.O. Box 2701
Gainesville, GA 30503
Copyright©2000 Linux Quick Command Reference $24.99 + $3.50 (Shipping)
ISBN: 0-9703083-2-9
1.1 Introduction 1.2.10 Referring To Home Directories 1.3.4 Copying Files
1.6 Exploring The File System 1.8 Wildcards 1.9.3 Pipes 1.10.3 Permissions Dependencies
1.12.4 Stopping And Restarting Jobs 1.13.3 Inserting Text 1.13.9 Including Other Files
1.14.3 Shell Initialization Scripts System Administration 2.3.1 The /etc/imitate file
2.4 Managing File Systems 2.6 Managing Users 2.6.5 Groups 2.7.2 gzip and compress
2.8.3 Making Backups To Tape Devices 2.9.1 Upgrading The Kernel
2.9.3 Installing A Device Driver Module
BOOK: LINUX QUICK COMMAND REFERENCE
http://personal.atl.bellsouth.net/~psadler
© copyright KnowledgeWorks, Inc. (2001)