Quick Refence of UNIX COMMAND

Unix Command Reference

General

Man:------ command Display the Unix manual entry describing a

given command

apropos :-----command Locate commands by keyword

alias -------name1 name2 Create command alias name

alias-------- name Display command alias

unalias --------name Remove command alias name

passwd --------Change password

quota-------- Display amount of disk space used

df --------Show available system disk space

du --------Show disk space being used up by folders

bc-------- Basic calculator

bc obase=16 255-------- Displays FF

bc ibase=16 obase=10

Hex to Dec

date --------Display date & time

cal --------month year Show calendar

whoami-------- Display current user

history --------Display recent commands

!! --------Repeat last shell command

! --------string Repeat last shell command that began

with string

! -------- nRepeat recent shell command n

Ctrl/p-------- (previous)

Move up in history list

Ctrl/n-------- (next)

Move down in history list

Ctrl/b-------- (backward)

Cursor left to edit command

Ctrl/f -------- (forward)

Cursor right to edit command

Ctrl/d -------- (delete)

Delete character in command

clear --------Clear terminal screen

lock --------Lock terminal

reset-------- Reset / initialize terminal

set--------Show environment

env--------Show current settings

sentenv name-------- v Set env var to value v (csh/tcsh)

export name="v" -------- Set environment variable to value v

(ksh/bash)

exit --------Terminate current session

script --------Make a typescript of everything printed on

the terminal

sudo /usr/libexec/locate.updatedb --------Update the locate database

File System Navigation

* Wild card: match zero or more characters

? Wild card: match zero or one character

. Shorthand for the current directory

.. Shorthand for the parent of the current

directory

~ Home directory

~username Home directory of user username

cd dir Change to directory dir

cd Return to home directory

pwdDisplay working directory

file file Determine file type

du -ks *|sort -nr|more Show all directory sizes in order, largest first

ls List the contents of the current directory

ls dir List the contents of the directory dir

ls -l Show permissions, owner, size, and otherfile info

ls –a Show all files, including (hidden) files that begin

with a dot

ls -R Show files recursively, for all subdirectories

ls -d List directories like other files, without

displaying their contents

ls -k List file sizes in kilobytes

ls -X Sort files by file extension

ls -1 Display the listing in 1 column

ls -t Show files in time order, newest to oldest

ls -l | grep "^d" List all directories in the current directory

without any of the files

ls -l | grep ^d | wc -l Find the number of subdirectories in the

current directory

ls -ls|sort -nr|more List files by size, largest first

Data Manipulation

mkdir dir Create new directory dir

cp file1 file2 Copy file(s)

cp file dir Copy file(s) into a directory

cp -r dir1 dir2 Copy a directory and, recursively, its subdirectories

mv file dir Move file to directory dir

mv dir1 dir2 If directory dir2 exists,move dir1 into dir2;

otherwise, rename dir1 as dir2

mv file1 file2 Rename file1 as file2

#!/bin/sh

for i in *

do

echo $i

mv $i `basename $i`.ext

done Rename a number of files

rm file Remove file

rm -f file Force, remove files without prompting

rm -r file Remove files, directories, and recursively,

any subdirectories

rmdir dir Remove empty directory dir

vi file Vi fullscreen editor

emacs file Emacs fullscreen editor

pico file Pico text editor

wc file Count lines,words,& chars

cat file List contents of file

more file Display contents of a file one screen at a

time

less file Opposite of more

head -n file Display first n lines of file

tail -n file Display last n lines of file

cmp file1 file2 Compare two files

diff file1 file2 Show file differences

cp file1 file2 Copy file file1 into file2

sort file Display the lines of text file alphabetically

sort -r file Sort in reverse order

sort -n file Sort numerically (2 before 10)

sort +n file Sort on n+1st field

cat file1 file2 > file3 Concatenate file1 & file2 into file3

split [-n] file Split file into n-line pieces

grep sample file Output lines that match sample string or

pattern

grep -i Case-insensitive search

grep -n Show the line # along with the matched

line

grep -v Invert match: find all lines that do not

match

grep -w Match entire words, rather than substrings

touch file Update the timestamp on a file, if the file

doesn’t exist, touch creates an empty file

I/O Redirection

The shell expects input from; and sends output

to, a terminal. To write command output

to files or read input from files, redirection is

used. UNIX defines three I/O units with corresponding

file descriptors:

0: stdin (standard input)

1: stdout (standard output)

2: stderr (standard error)

prog > file Redirect (write) stdout of prog to file

prog >> file Append stdout of prog to file

prog < file Read stdin for prog from file

prog < file1 > file2 Read stdin for prog from file1, redirect

stdout to file2

prog 2>file Write stderr of prog to file

prog 2>&1 With file descriptor: write stderr of prog

to stdout

cmd1 | cmd2 Pipeline:use cmd1’s output as input for cmd2

cmd1 && cmd2 cmd2 is executed only if the execution of

cmd1 ends up successfully

cmd1 || cmd2 cmd2 is executed only if the execution of

cmd1 does not end up successfully

cmd1 ; cmd2 Execute cmd2 after execution of cmd1 stopped

nohup command < file.in >> file.out& ’No hangup’: execution of command will

continue even if the user logs off the

system (exit). Run command in the bakkground

(&), taking input from file.in and

appending output to file.out.

Permissions

-rwxr-xr-x Directories have a d in the first column;

regular files have a –. The remaining 9 characters indicate the

owner, group, and world permissions of the

file.

An r indicates that the file is readable; w is

writable, and x is executable.

A dash in the column instead of a letter

means that particular permission is turned

off.

t is the ’sticky bit’ for directories; prevents

files from being deleted by anyone

other than the owner.

s is the ’setuid-bit’ for files; execute a program

using the owner’s permissions (rather

than those of the one who calls it).

Setting Permissions with Letters

chmod u+rwx,go+rx file

u is the user’s (owner) permissions; g is the

group permissions, and o is world (other)

permissions.

The + sign turns the stated permissions on;

a – sign turns them off.

Directories should always have, at least for

the owner, the x permission set.

A directory doesn’t have to be readable for

the web server to read and execute files

within that directory. Only the files themselves

must be readable.

Numeric Permissions

chmod 711 file Change permissions on a file.

The first number translates to permissions

by the owner (logon account). The second

is permissions for the group (a possibly

empty group of logon accounts). The third

is permissions for everyone.

0: --- (no permissions)

1: --x (executable only)

2: -w- (writable only)

3: -wx (writable and executable)

4: r--- (readable only)

5: r-x (readable and executable)

6: rw- (readable and writable)

7: rwx (readable, writable, and executable)

File Compression

compress file Reduce the size of a file

uncompress file Restore a compressed file

tar cf - /home/file | compress >

file.tar.Z tar and compress a file

tar cf - /home/file | gzip >

file.tar.Z tar and gzip a file

ls -al | awk '$0!~/^d/ {print $9}' |

xargs tar cvf archive_name.tar Archive only regular files in a directory,

omitting subdirectories and hidden files

Make an index file of the contents

of the tar file

tar cvf - /home/file

2>file.idx | compress > file.tar.Z For sh, ksh

(tar cvf - /home/file | compress >

/file.tar.Z) >&file.idx For csh

A simple backup script

sh:

% pico ~/bin/backup.sh

#!/bin/sh

echo "Backup of Folder:"

tar cvf - /home/file 2>file.idx |

gzip > home/file.tar.Z

Save the script in ~/bin

% chmod +x ~/bin/backup.sh Make it executable

% rehash Force the shell to rebuild its list of known

executables

Networking & Communications

whoList logged in users

finger user Display user information

chfn Change finger information

ping host Send ICMP ECHO_REQUEST packets to network

hosts

telnet hostname Connect to another remote system using

the telnet protocol

ssh host

rsh host Log into and execute commands on a

remote machine

lpr -P printer file Output file to line printer

mail user Send mail to user

biff y/n Instant notification of mail

Process Control

sleep n Sleep for n seconds

jobs Display list of jobs

Ctrl/c Interrupt process / stop execution of a

command

Ctrl/d End of typed input (End of File Key)

Ctrl/q Start / resume terminal output

Ctrl/s Stop terminal output

Ctrl/z Suspend execution of a command

ps Show process status statistics

ps aux Show complete process listing

topShow system usage statistics dynamically;

stop with q

kill -9 n Remove process n

stop %n Suspend background job n

command& Run command in background

bg %n Resume background job n

fg %n Resume foreground job n

By : Homera Durani

UNIX BASIC COMMANDS

Directories

• mkdir dirname --- make a new directory
• cd dirname --- change directory. You basically 'go' to another directory, and you will see the files in that directory when you do 'ls'. You always start out in your 'home directory', and you can get back there by typing 'cd' without arguments. 'cd ..' will get you one level up from your current position. You don't have to walk along step by step - you can make big leaps or avoid walking around by specifying pathnames.
• pwd --- tells you where you currently are. 

About other people

• w --- tells you who's logged in, and what they're doing. Especially useful: the 'idle' part. This allows you to see whether they're actually sitting there typing away at their keyboards right at the moment.
• who --- tells you who's logged on, and where they're coming from. Useful if you're looking for someone who's actually physically in the same building as you, or in some other particular location.
• finger username --- gives you lots of information about that user, e.g. when they last read their mail and whether they're logged in. Often people put other practical information, such as phone numbers and addresses, in a file called .plan. This information is also displayed by 'finger'.
• last -1 username --- tells you when the user last logged on and off and from where. Without any options, last will give you a list of everyone's logins.
• talk username --- lets you have a (typed) conversation with another user
• write username --- lets you exchange one-line messages with another user
• elm --- lets you send e-mail messages to people around the world (and, of course, read them). It's not the only mailer you can use, but the one we recommend. See the elm page, and find out about the departmental mailing lists (which you can also find in /user/linguistics/helpfile). 

About your (electronic) self

• whoami --- returns your username. Sounds useless, but isn't. You may need to find out who it is who forgot to log out somewhere, and make sure *you* have logged out.
• finger & .plan files
  of course you can finger yourself, too. That can be useful e.g. as a quick check whether you got new mail. Try to create a useful .plan file soon. Look at other people's .plan files for ideas. The file needs to be readable for everyone in order to be visible through 'finger'. Do 'chmod a+r .plan' if necessary. You should realize that this information is accessible from anywhere in the world, not just to other people on turing.
• passwd --- lets you change your password, which you should do regularly (at least once a year). See the LRB guide and/or look at help password.
• ps -u yourusername --- lists your processes. Contains lots of information about them, including the process ID, which you need if you have to kill a process. Normally, when you have been kicked out of a dialin session or have otherwise managed to get yourself disconnected abruptly, this list will contain the processes you need to kill. Those may include the shell (tcsh or whatever you're using), and anything you were running, for example emacs or elm. Be careful not to kill your current shell - the one with the number closer to the one of the ps command you're currently running. But if it happens, don't panic. Just try again :) If you're using an X-display you may have to kill some X processes before you can start them again. These will show only when you use ps -efl, because they're root processes.
• kill PID --- kills (ends) the processes with the ID you gave. This works only for your own processes, of course. Get the ID by using ps. If the process doesn't 'die' properly, use the option -9. But attempt without that option first, because it doesn't give the process a chance to finish possibly important business before dying. You may need to kill processes for example if your modem connection was interrupted and you didn't get logged out properly, which sometimes happens.
• quota -v --- show what your disk quota is (i.e. how much space you have to store files), how much you're actually using, and in case you've exceeded your quota (which you'll be given an automatic warning about by the system) how much time you have left to sort them out (by deleting or gzipping some, or moving them to your own computer).
• du filename --- shows the disk usage of the files and directories in filename (without argument the current directory is used). du -s gives only a total.
• last yourusername --- lists your last logins. Can be a useful memory aid for when you were where, how long you've been working for, and keeping track of your phonebill if you're making a non-local phonecall for dialling in. 

Files

• ls --- lists your files
  ls -l --- lists your files in 'long format', which contains lots of useful information, e.g. the exact size of the file, who owns the file and who has the right to look at it, and when it was last modified.
  ls -a --- lists all files, including the ones whose filenames begin in a dot, which you do not always want to see.
  There are many more options, for example to list files by size, by date, recursively etc.
• more filename --- shows the first part of a file, just as much as will fit on one screen. Just hit the space bar to see more or q to quit. You can use /pattern to search for a pattern.
• emacs filename --- is an editor that lets you create and edit a file. See the emacs page.
• mv filename1 filename2 --- moves a file (i.e. gives it a different name, or moves it into a different directory (see below)
• cp filename1 filename2 --- copies a file
• rm filename --- removes a file. It is wise to use the option rm -i, which will ask you for confirmation before actually deleting anything. You can make this your default by making an alias in your .cshrc file.
• diff filename1 filename2 --- compares files, and shows where they differ
• wc filename --- tells you how many lines, words, and characters there are in a file
• chmod options filename --- lets you change the read, write, and execute permissions on your files. The default is that only you can look at them and change them, but you may sometimes want to change these permissions. For example, chmod o+r filename will make the file readable for everyone, and chmod o-r filename will make it unreadable for others again. Note that for someone to be able to actually look at the file the directories it is in need to be at least executable. See help protection for more details.
• File Compression
  • gzip filename --- compresses files, so that they take up much less space. Usually text files compress to about half their original size, but it depends very much on the size of the file and the nature of the contents. There are other tools for this purpose, too (e.g. compress), but gzip usually gives the highest compression rate. Gzip produces files with the ending '.gz' appended to the original filename.
  • gunzip filename --- uncompresses files compressed by gzip.
  • gzcat filename --- lets you look at a gzipped file without actually having to gunzip it (same as gunzip -c). You can even print it directly, using gzcat filename | lpr
• printing
  • lpr filename --- print. Use the -P option to specify the printer name if you want to use a printer other than your default printer. For example, if you want to print double-sided, use 'lpr -Pvalkyr-d', or if you're at CSLI, you may want to use 'lpr -Pcord115-d'. See 'help printers' for more information about printers and their locations.
  • lpq --- check out the printer queue, e.g. to get the number needed for removal, or to see how many other files will be printed before yours will come out
  • lprm jobnumber --- remove something from the printer queue. You can find the job number by using lpq. Theoretically you also have to specify a printer name, but this isn't necessary as long as you use your default printer in the department.
  • genscript --- converts plain text files into postscript for printing, and gives you some options for formatting. Consider

    Finding things

  • ff --- find files anywhere on the system. This can be extremely useful if you've forgotten in which directory you put a file, but do remember the name. In fact, if you use ff -p you don't even need the full name, just the beginning. This can also be useful for finding other things on the system, e.g. documentation.
  • grep string filename(s) --- looks for the string in the files. This can be useful a lot of purposes, e.g. finding the right file among many, figuring out which is the right version of something, and even doing serious corpus work. grep comes in several varieties (grep, egrep, and fgrep) and has a lot of very flexible options. Check out the man pages if this sounds good to you.
  • making an alias like alias ecop 'genscript -2 -r \!* | lpr -h -Pvalkyr' to print two pages on one piece of paper.
  • dvips filename --- print .dvi files (i.e. files produced by LaTeX). You can use dviselect to print only selected pages. See the LaTeX page for more information about how to save paper when printing drafts. 
  
  

Miscellaneous tools

• webster word --- looks up the word in an electronic version of Webster's dictionary and returns the definition(s)
• date --- shows the current date and time.
• cal --- shows a calendar of the current month. Use e.g., 'cal 10 1995' to get that for October 95, or 'cal 1995' to get the whole year.