Unix Commands:
(a working command set)
Prof. Michael P. Harris, CCNA, CCAI
ITSC1405 – PC Operating Systems
adduser, useradd
used by root to add user to system. Usage: adduser userid
alias, unalias
assign name to specified command list. e.g. create a macro command
ash, bsh
a shell, a very simple shell program sometimes used on boot diskettes.
at
executes a shell script at specified time. Usage: at [-f] file time
atq, atrm
atq shows, and atrm removes, pending jobs queued by at.
awk, gawk, nawk
searches for and process patterns in a file. A shell scripting language.
banner
print banner to standard output. Usage: banner [option] [characters]
bash
Bourne Again SHell. This is the default shell in most Linux installations
bzip, bzip2
compresses files with an algorithm different from gzip.
bunzip, bunzip2
used to uncompress files compressed with bzip.
bzless
view bzipped files
cc, c++
invokes C and C++ program compilers. See also gcc, g++, yacc
cal
displays a 12-month or a one-month calendar. Usage: cal [month] year
cat
concatenate/combine stdin to stdout. Used to join or display files.
cd
change working directory. Usage: cd path, cd –or- cd ~, cd ..
cfdisk
similar to fdisk, but menu-driven. See also fsck
chmod
set permissions (access modes) of files or directories. See also umask
chgrp
changes the group associated with file. Usage: chgrp [-R] group files
chown
changes the user-ownership of a file. Usage: chown [-R] userid files
chsh
change default shell. See also: sh, ash, bash, csh, ksh, tcsh
clear
clear screen command (tput clear)
cmp
compares two files for differences. See diff, diff3, uniq
comm
compares sorted files
compress
compress (uncompress) files to the older .Z file format. See gzip, zcat
cp
copies on or more files. Usage cp [-r][-p] source target[directory]
crontab
schedules command to run at regularly specified time. See also at.
csh
the C shell, See also ash, bash, ksh, and sh.
csplit
separate files into sections. See also split, cut, paste.
cut
selects characters or TABed fields from files/lines of input. See paste
date
displays or sets date and time. See also time. Usage: date [date]
df
displays disk free space & disk capacity in blocks on physical devices.
diff
diff3
displays differences between two files. See also: cmp, comm, uniq
compares three files and reports on differences
du
displays information on disk usage & file sizes. Ex. du / -bh | less
echo
write arguments to standard output. Ex. echo $PATH, echo ~
emacs
a very powerful screen oriented text editor.
env, printenv
display or set to a new value, the environmental setting variables.
eval
scans and evaluates the command line. See also: let, expr, test
ex
interactive command-based editor. See vim, an improved version of vi.
exec
system call which creates a subshell to execute a binary or a script.
exit
exit (terminate) a command-line shell.
expand
convert tabs in files to spaces and write to standard output.
export
place the value of a variable in the set environment (makes it global).
expr
evaluate an expression and displays the result. See also: let, eval, test
false
null command that returns an unsuccessful exit status. See also true
fc
views, edits, and executes commands from the shell history list.
fdisk
utility used to partition hard drives. See: cfdisk. Usage: fdisk device
file
displays classification of a file(s) based on the type of data within.
find
find files matching a large variety of search criteria. Ex. find . –type d
finger
display information about a specified userid or userids. See also: id
fmt
simple text formatting utility. Makes lines the same length. See pr
fold
break lines of files so they are no wider than a given length. See fmt
free
gives used/free system memory along with other useful information.
fsck
File System Check and Repair.
ftp
file transfer (protocol) over the network.
gcc, g++
invoke the GNU C or C++ compiler. See also cc, c++, yacc
gawk, nawk
GNU awk, mostly for processing delimited text files
gimp
a very powerful image manipulation and paint program
grep, fgrep, egrep
find a string or pattern within a file(s). Usage: grep pattern files
groupadd
create a new group on the system.
groups
shows which groups you are in.
grub
GNU GRand Unified Bootloader. Boot multiple OSs. See also: lilo
gvim
GNU Vi IMproved. See also: vi, view, and vim
gzip, gunzip
utility used to compress or uncompress files. (.tar.gz or .tgz)
halt
shut down system as root, without reboot, immediately. See shutdown
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hash
remembers the location of commands in the search path.
head
displays first part (10 lines default) of a file. See tail
history
command for viewing and manipulating the shell command history list
host
look up host names using domain server. See also: hostname, uname
hostname
used to get/set the hostname (computername). See /etc/HOSTNAME
id
display your userid and groupid. See also: logname, groups, whoami
inetd
daemon which starts other daemons on demand. See /etc/inetd.conf
ifconfig
display information on network interfaces that are currently active.
ifdown
shut down the network interface. Usage: ifdown [interface_name]
ifup
start up the network interface. Usage: ifup [interface_name]
info
display system information. This is the GNU hypertext reader.
init
master process, runs at bootup, executes commands in /etc/inittab
jed, joe, jove
programmer's text file editors, have emacs emulation modes.
kill
sends a signal to terminate a job or process. Ex. kill -9 pid
ksh
Korn shell. See sh, ash, bash, and csh
ldd
list/locate the shared libraries on which a given executable depends.
less
improved more command. Displays text files, many options. See pg
let
evaluates a numeric expression & assigns answer. See: expr, eval, test
lilo
LInux LOader, installs a boot loader on the boot sector of a device.
ln
creates a link to a file. Used to create hard links and -s symbolic links.
locate
find file(s) that that match a pattern, easier syntax than find.
login
login to the Unix/Linux operating system. See also: logout
logname
consult /etc/utmp for user's login name. See also: id, hostname
logout
execute logout as individual user and bring up login: prompt
look
look for strings in files, See grep
lpr
send file to be printed, used with pr. See also lp
lpq
show print jobs that are waiting
lprm
cancel a job from print queue
ls
list directory contents. ls –al, ls –color=auto, ls –FAC, ls –FRAC, ls –Fskb
make
keeps a set of programs current, works by executing a script makefile.
man , --help
displays information from online Unix reference manual. See: whatis
mc
Midnight Commander file manager and visual shell
mkdir
make (create) a directory. See also: cd, rmdir, rm –rd, mv
mkfs
make (create) a file system (format) on a device or partition. See dd
Unix commands:
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mkswap
creates a Linux swap space on the specified hard disk partition.
more
list file contents, stopping after each full screen. Q exits. See less, pg
mount , umount
mount a device as a directory in the filesystem. See also: /etc/fstab
mv
moves (renames) files/directories.
netconf
used (as root) to set up the network. See also: ifconfig
nice
sets the priority of a program. Usage: nice program_name
od
dumps contents of a file.
passwd
change login password.
paste
joins corresponding lines from files. See cut, split
pathchk
determine validity and portability of filenames.
perl
Practical Extraction and Report Language
pg
display data one screenful at a time. See more, less
pico
simple screen oriented text editor. See also nano
ping
check if an Internet computer is responding (online). See traceroute
pr
paginates files for printing, used with lpr. See also fmt
ps
displays processes status. Usage: ps -a for all processes. See kill, top
pstree
display processes in the form of a parent/child tree structure.
pwd
print absolute path of the working (current) directory.
python
interpreted, interactive, object-oriented programming language
rcp
copy one or more files to or from a remote computer. See rsh, rlogin
read
reads line from standard input. See echo
rlogin
log in to remote computer. Ex: rlogin -l userid mercury.delmar.edu
rm
remove files or (-rd) directories. Usage: rm [-r] [-rd] filepath
rmdir
remove empty directories. See also rm –rd
rmuser
remove user account from the filesystem. See also: userdel, adduser
route
show the routing table entries. Usage: route [-n]
rpm
invokes the Redhat Package Manager in command line mode.
rpm2tgz
an extremely useful utility that converts rpm packages to tgz format.
rsh
execute shell command on a remote computer. See rcp, rlogin, & ssh
rxvt
a terminal program like xterm, has less features/uses less memory.
sed
edits a file (stream/redirect). Also a tool for processing text files.
set, setenv
set or display value of shell variables. See also env, export, let
sh
standard UNIX Bourne shell. See also: ash, bash, csh, and ksh
shutdown
reboot or shut down system as root. shutdown [-h] [-r] minutes
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sleep
creates process that sleeps for specified interval. See also: wait
sort
sorts and/or merge files.
split
split file into specified number of segments. See also csplit, cut, paste
ssh
secure shell with security and encryption. See telnet, rlogin, rsh
startx
frontend to xinit (xterm) starts X-clients/ X-server window managers.
su
simulate user. log in as another user, including root (super user).
sudo
Super User DO, gives users root permission to perform specified tasks.
swapon, swapoff
enables or disables swap disk usage.
symlinks
provide list of and information about symbolic links. See ln -s
sync
writes memory buffers to physical devices for safe removal.
tail
displays the last part (default 10 lines) of a file. See head
tar
tape archive, file compression/archiving utility. tar [–xvf] [-cvf] file.tar
tcsh
extended version of the C shell, csh
tee
copy standard input to standard output and to one or more files
telnet
remote login over the network. See also ssh, rsh, rlogin
test
evaluates an expression or compares arguments. See expr, eval
tftp
user interface to TFTP (trivial FTP) protocol. See also: ftp, rcp
time
displays times for the current shell and its children. See also date
top
dynamically displays process status. See also ps, kill
touch
create an empty file or update access and modification times of a file.
tr
translation utility, replace specified characters in a text file.
true
a null command that returns a successful exit status. See false
tty
shows special file that represents your terminal & terminal pathname.
umask
establishes the file-creation permissions mask. Usage: umask xyz
umount
finish writing to the device and remove it from the active filesystem.
uname
displays information about the OS system. Usage: uname [-a]
uniq
displays lines of a file that are unique. See also diff, cmp, comm
unzip
uncompress files compressed with zip, compatible with DOS PKzip
uptime
shows the time, system up time, number of users, & average load.
userdel
remove an account (as root). The user's home directory is not deleted.
users
prints list of users on the system. See also who, whodo
vdir
variant of the ls command. Defaults to printing the long listing.
vi
Unix commands:
standard screen oriented Unix editor. See also: vim, gvim, and view
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view
vi in read-only mode
vim
Vi IMproved, vi editor. See also: vi, gvim, and view
wait
waits for a background process to terminate. See also: sleep
wc
word count, displays number of lines, characters and words in a file
whatis
display one-line summary about a specified command. See also: man
whereis
used to find utilities/files in standard locations.
which
used to find utilities/files in the search path.
who
display information about currently logged in userids. See also: id
whoami, who am i
display information about userid that is currently logged in. See id
xterm
start an X-Window terminal session. See also: rxvt
yacc
parser generator. Yet Another C Compiler
zcat
read to stdout files that have been compressed with gzip or compress.
zcmp
read compressed files and pass them to cmp.
zdiff
read compressed files and pass them to diff.
zgrep
read compressed files and pass them to grep.
zip, unzip
zip compress/uncompress utility compatible with DOS PKzip
zless
view zipped files
zmore
print contents of compressed files one screen at a time
znew
uncompress .Z files (compress) and recompress in .gz (gzip) format.
Unix commands:
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