Quick Unix Tutorial.doc

Quick Unix Tutorial Examples of Basic Commands Action appent to file

Command cat >> cat >>

Examples cat >> cat >> file1

combine 2 files cat

cat file1 file2 > file3

copy files

cp

cp myfile copymyfile

create a file

cat

cat > newfile

edit files

vi

vi file

list files

ls

ls bin/

move a file

mv

mv file1 doc/chapter1

remove a file

rm

rm unwantedfile

rename a file

mv

mv oldfilename ne wfilename

view files

cat pg more less view

cat file cat file pg file2 file3 view file6 file7

Directories

Command

Examples

change to another directory cd

cd example/first/

create a directory

mkdir

mkdir example1  

find out where you are

pwd

pwd

go to your home directory

cd

cd

remove an emplty eirectory rmdir

rmdir jun  

Redirection of Output or nput ! redirects the output of a command command to a file !! redircts the output of a command to to the end of an existing file " taes the the input of a command form form a file! not the the terminal terminal

#ummar$ of Basic Commands • • •

apropos apropos"1# apropos"1# locate  locate commands by eyword looup arc% arch"1$# display the architecture of the current host cal cal"1# cal"1# display  display a calendar cal %month& year  o month number between 1 and 12 o year number between 1 and '''' Examples& cal '(() print calendar for year 1''6 cal ' '((* print calendar for (anuary 1''7

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cancel lp"1# lp"1# send/cancel  send/cancel re)uests to an *+ print service cat cat"1# cat"1# concatenate  concatenate and display files ",o ",o view files! create files! append to files and combine files# cat %options& %files& Examples& cat files read file"s# cat ! file create file "reads form terminal- terminate input with .# cat !! file append to file "reads form terminal- terminate input with .# file2 to to file1 file1 cat file+ !! file' appends contents of file2 cd cd"1# shell built0in functions to change the current woring directory c%dir cd"1# c%dir  cd"1# shell  shell built0in functions to change the current woring directory c%grp chgrp"1# chgrp"1# change  change the group ownership of a file c%mod chmod"1# chmod"1# change  change the permissions mode of a file c%own chown"1# chown"1# change  change owner of file clear clear"1# clear clear"1# clear  clear the terminal screen cp cp"1# copy files date date"1# date"1# print  print and set the date dc dc"1# arbitrary precision destop calculator dos+unix dos2unix"1# dos2unix"1# convert  convert text file from  format to  format e,ect eject"1# eject"1# eject  eject media such as 405 and floppy from drive exit exit"1# exit"1# shell  shell built0in functions to enable the execution of the shell to advance beyond its se)uence of steps file file"1# file"1$# file"1$# determine  determine the type of a file by examining its contents %ead head"1# head"1# display  display first few lines of files lp lp"1# lp"1# send/cancel  send/cancel re)uests to an *+ print service lpstat lpstat"1# lpstat"1# print  print information about the status of the *+ print service ls ls"1# ls"1$# list the contents of a directory ls %options& %directories& the current woring directory used if no directories specified   few options8 o 0a list all entries includeing hidden files files "starting with 9# o 0i print inode numbers o 0l long list "mode! lins! lins! owner! owner! group! group! si:e! timeof last last modification! modification! and name o 0t sort by modification time o 0x multi0column list! sorted across each row -ail! -ail! mailx mailx"1# mailx"1#!! mail mail"1# rmail interactive rmail interactive message processing system to read mail or send mail to users mail %options& users Examples& mail with no options! to read your mail mail user to send mail to user  mail user ; filename mail a file to another user  mkdir mdir"1# mkdir mdir"1# mae  mae directories more more"1# browse or page through a text file mv mv"1# mv"1# move  move files nispasswd"1# change  change ou can use the rmdir command to remove a directory $ma"e sure it is empty first& -ry to remove the backups directory >ou will not be able to since UNIX will not let you remove a non#empty directory

01ercise ,b 3reate a directory called tempstuff  using mkdir , then remove it using the rmdir command

,$2 Displaying the contents of a file on the screen clear (clear screen) !efore you start the net section, you may li"e to clear the terminal window of the previous commands so the output of the following commands can be clearly understood

7t the prompt, type

% clear

-his will clear all tet and leave you with the 8 prompt at the top of the window

cat (concatenate) -he command cat can be used to display the contents of a file on the screen -ype

% cat science.txt

7s you can see, the file is longer than than the siCe of the window, so it scrolls past ma"ing it unreadable

less -he command less writes the contents of a file onto the screen a page at a time -ype

% less science.txt

4ress the space+bar: if you want to see another page, and type  9: if you want to *uit reading 7s you can see, less is used in preference to cat for long files

head -he head   command writes the first ten lines of a file to the screen

2irst clear the screen then type

% head science.txt

-hen type

% head - science.txt

(hat difference did the #D do to the head commandB

tail -he tail command writes the last ten lines of a file to the screen

3lear the screen and type

% tail science.txt

E )ow can you view the last 1D lines of the fileB

,$! Searching the contents of a file

Simple searching using less Using less, you can search though a tet file for a "eyword $pattern& 2or eample, to search through science$t1t for the word :science:, type

% less science.txt

then, still in less, type a forward slash %: followed by the word to search

/science

7s you can see, less finds and highlights the "eyword -ype  n: to search for the net occurrence of  the word

grep (don:t ask 4hy it is called grep) !rep is one of many standard UNIX utilities It searches files for specified words or patterns 2irst

clear the screen, then type

% !rep science science.txt

7s you can see, !rep has printed out each line containg the word science

r has it BBBB

-ry typing

% !rep "cience science.txt

-he !rep command is case sensitive5 it distinguishes between .cience and science

-o ignore upper/lower case distinctions, use the #i option, ie type

% !rep -i science science.txt

-o search for a phrase or pattern, you must enclose it in single *uotes $the apostrophe symbol& 2or eample to search for spinning top, type

% !rep -i #spinnin! top# science.txt

.ome of the other options of grep are

+# display those lines that do N- match +n precede each matching line with the line number +c print only the total count of matched lines

-ry some of them and see the different results ou should now have two files ne contains si fruit, the other contains four fruit

(e will now use the cat command to @oin $concatenate& list" and list, into a new file called biglist -ype

% cat list list $ bi!list

(hat this is doing is reading the contents of list" and list, in turn, then outputing the tet to the file biglist

-o read the contents of the new file, type

% cat bi!list

.$. 7edirecting the Input (e use the J symbol to redirect the input of a command

-he command sort alphabetically or numerically sorts a list -ype

% sort

-hen type in the names of some animals 4ress Aeturn: after each one

do! cat  bird  ape &' control d to stop

-he output will be

ape  bird cat do!

Using J you can redirect the input to come from a file rather than the "eyboard 2or eample, to sort the list of fruit, type

% sort 0 bi!list

and the sorted list will be output to the screen

-o output the sorted list to a file, type,

% sort 0 bi!list $ slist

Use cat to read the contents of the file slist

.$2 3ipes -o see who is on the system with you, type

% who

ne method to get a sorted list of names is to type,

% who $ names.txt % sort 0 names.txt

-his is a bit slow and you have to remember to remove the temporary file called names when you have finished (hat you really want to do is connect the output of the who command directly to the input of the sort command -his is eactly what pipes do -he symbol for a pipe is the vertical bar K

2or eample, typing

% who 1 sort

will give the same result as above, but *uic"er and cleaner

-o find out how many users are logged on, type

% who 1 wc -l

01ercise .b Using pipes, display all lines of list" and list, containing the letter +p+, and sort the result

7nswer available here

Summary

/ommand

-eaning

 $ file command 

redirect standard output to a file

 $$ file command 

append standard output to a file

 0 file command 

redirect standard input from a file

command1  1 command2 

pipe the output of command1 to the input of commandF

cat file1 file2   $ file0  concatenate file1 and fileF to file0

sort

 who

sort data

list users currently logged in

'.toneban"Gsurreyacu", H 9th ctober F000

UNIX Tutorial Four 2$" Wildcards The = 4ildcard -he character 2 is called a wildcard, and will match against none or more character$s& in a file $or directory& name 2or eample, in your uni1stuff  directory, type

% ls list2

-his will list all files in the current directory starting with list$$$$

-ry typing

% ls 2list

-his will list all files in the current directory ending with $$$$list

The ? 4ildcard -he character 3 will match eactly one character .o ?ouse will match files li"e house and mouse, but not grouse -ry typing

% ls 3list

2$, Filename con#entions (e should note here that a directory is merely a special type of file .o the rules and conventions for naming files apply also to directories

In naming files, characters with special meanings such as % = >  , should be avoided 7lso, avoid using spaces within names -he safest way to name a file is to use only alphanumeric characters, that is, letters and numbers, together with L $underscore& and  $dot&

@ood filenames

Aad filenames

pro@ecttt

pro@ect

myLbigLprogramc

my big programc

fredLdavedoc

fred M davedoc

2ile names conventionally start with a lower#case letter, and may end with a dot followed by a group of letters indicating the contents of the file 2or eample, all files consisting of 3 code may be named with the ending $c, for eample, prog"$c  -hen in order to list all files containing 3 code in your home directory, you need only type ls 2.c in that directory

2$. @etting Belp &n+line -anuals -here are on#line manuals which gives information about most commands -he manual pages tell you which options a particular command can ta"e, and how each option modifies the behaviour of the command -ype man command    to read the manual page for a particular command

2or eample, to find out more about the wc $word count& command, type

% man wc

7lternatively

% whatis wc

gives a one#line description of the command, but omits any information about options etc

B

'ore eamples of environment variables are

•

U.;A $your login name&

•

)'; $the path name of your home directory&

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).- $the name of the computer you are using&

•

7A3) $the architecture of the computers processor&

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$the name of the computer screen to display X windows&

•

4AIN-;A $the default printer to send print @obs&

•

47-) $the directories the shell should search to find a command&

Finding out the current #alues of these #ariables$

;NIAN';N- variables are set using the setenv command, displayed using the printenv or env commands, and unset using the unsetenv command

-o show all values of these variables, type

% printenv 1 less

M$. Shell ariables 7n eample of a shell variable is the history variable -he value of this is how many shell commands to save, allow the user to scroll bac" through all the commands they have previously entered -ype

% echo Lhistory

'ore eamples of shell variables are

•

cwd $your current wor"ing directory&

•

home $the path name of your home directory&

•

path $the directories the shell should search to find a command&

•

prompt $the tet string used to prompt for interactive commands shell your login shell&

Finding out the current #alues of these #ariables$ .); variables are both set and displayed using the set command -hey can be unset by using the unset command

-o show all values of these variables, type

% set 1 less

So 4hat is the difference bet4een 3 set the value of history, you will need to add the set command to the cshrc file

2irst open the $cshrc file in a tet editor 7n easy, user#friendly editor to use is nedit

% nedit ~/.cshrc

7dd the following line 72-;A the list of other commands

set history V F00

.ave the file and force the shell to reread its cshrc file buy using the shell source command

% source .cshrc

3hec" this has wor"ed by typing

% echo Lhistory

M$5 Setting the path (hen you type a command, your path $or 47-)& variable defines in which directories the shell will loo" to find the command you typed If the system returns a message saying =command 3ommand not found=, this indicates that either the command doesn+t eist at all on the system or it is simply not in your path

2or eample, to run units, you either need to directly specify the units path $6%units"K2%bin%units&, or you need to have the directory 6%units"K2%bin in your path

>ou can add it to the end of your eisting path $the Lpath represents this& by issuing the command

% set path K Lpath ~/unitsE6/bin

-est that this wor"ed by trying to run units in any directory other that where units is actually located

% cd  % units

-o add this path 4;A'7N;N->, add the following line to your cshrc 72-;A the list of other commands

set path K Lpath ~/unitsE6/bin