These exercises are to help you to become familiar with directory and file management.

Transcription

1 INFO230 - UNIX PRACTICAL EXERCISE INTRODUCTION TO THE WORKSTATION The workstation environment is one you will be using to do your work. This project unit is designed to help you to become familiarised with that environment. This includes how the windowing system works and can be customised, how to use the various unix commands, the unix C shell environment and an appreciation of the networking capabilities. 1.2 Exercises Workstation appearance When you start up you should also see a help viewer window which introduces and explains the CDE (Common Desktop Environment). Read through some of the introductory material there about windows, logging in and out, screen appearance, the mouse, keyboard etc. THE CDE has a set of control menus accessed by buttons in the front panel at the bottom of the screen. Its appearance, in descriptive form, is as follows: File manager Personal apps Mailer Printers Style manager Calandar Clock Netstation apps Work space Exit Application manager Help Trash can Using the style manager to configure the following according to your own preferences: 1. Select a suitable colour scheme for windows, menus etc. 2. Choose a back-drop. 3. Choose a screen saver. 4. Choose whether you want right- or left-handed mouse operation. Starting applications Find and practice starting up the following applications: 1. Netscape 2. The mailer - practice sending yourself or to a friend a mail message 3. Find how to start up the digital clock (you may need to search through a few menus to do that) 4. Practice creating some new terminal (dterm) windows. - Practice moving, iconing and closing these windows. UP.1

2 Moving between workspaces There are 4 workspaces you can work in. Create a new dterm and practice moving that window between different workspaces. e.g. Create the window initially in workspace 1, then move it to workspace 3, then to workspace 4 and then back to workspace INTRODUCTION TO UNIX These exercises are to help you to become familiar with directory and file management Introductory exercises 1. Make a directory in your home directory called practice. It will be used to do the exercises in this project unit. Change directories so this is your current directory. 2. Verify the path by using the pwd command. 3. Copy the file /usr1/student/info230/work.tar into this directory. It contains files and subdirectories in archive format that you will need to do the exercises. 4. Execute the command below to expand the archive you just copied. (the % sign is a general symbol that is used to refer to the command line prompt and should not be typed) % tar xf work.tar 5. Examine the files and directories using the ls command. 6. List the contents of subdirectories using the ls -R command. 7. Change your current directory to prac1. 8. Are there any hidden files inside prac1? 9. How large these files? 10. Use the file manager to examine your home directory and the files you just copied and created Directory creation and deletion 1. Make a directory inside prac1 called temp 2. Create its existence and contents in directory prac1 using ls 3. Now copy the file a.c into temp 4. Try to remove the directory using the rmdir command. 5. Enter the temp directory, remove the file a.c and return to prac1 6. Now remove the directory temp UP.2

3 1. 6 Filename expansion Filename expansion is used as a general technique and not just for use with the ls of cp commands. With ~/practice/prac1 as your current directory examine the operation of the following commands: % echo * % echo *.c % echo *.* % echo chapt? % echo chapt[123] % echo chapt[123456] % echo chapt[1-3] % echo chapt[1-6] % echo help{a,b,c}.doc wc, cat, more and sort commands 1. Display the contents of the file fruit and veg using the cat command. 2. Use the wc command to show how many lines, words and characters are in these files. 3. fruit and veg are not sorted. Use the sort command to sort both of these files in increasing alphabetical order. 4. Combine the fruit and veg files as follows % cat fruit veg > produce (This uses output redirection to redirect the output of the cat fruit veg from the screen to the file produce. 5. Display this file using the more command. % more produce 6. Sort this file in reverse alphabetic order and display it by piping it into more % sort -r produce more 7. Display the first 10 lines and then the last 10 lines of produces as follows: % head produce % tail produce 8. How would you display the first 15 lines? UP.3

4 1. 8 INTRODUCTION TO SHELL SCRIPTS Since we have not yet cover vi, use the text editor to create the following scripts in the directory ~/practice/prac1. The text editor has not been covered in lectures but it is a simple easy-to-use text editor using a graphical interface Shell variables and echo Create the following script story!/bin/csh echo It was a dark and stormy night echo Jack and Jill went up the hill echo Suddenly a shot rang out echo Jack fell down and broke his crown echo And Jill came tumbling after WARNING: Do not forget to put a CARRIAGE RETURN after the last line of the script. If you do not, it is incomplete and will be not be interpreted. This applies to all scripts that you create. 1. Run this script by typing % chmod u+x story % story 2. Now run this script by typing % source story 3. Copy this script into the file story2 and modify it so that Jack and Jill are replaced by two shell variables $char1 and $char2 contained in the script. Test this script by typing 1.10 % story2 To examine more of the power of shell scripts, create the following script: welcome!/bin/csh echo Hello $user echo Today is `date` echo I feel $argv[1] today echo The following users are logged in: `users` UP.4

5 1. Test the script by typing: % chmod u+x welcome % welcome good 2. Look up the lecture notes to explain what: (i) $user does in line 3 (ii) `date` does in line 4 (iii) $argv[1] does in line 5 (iv) `users` does in line 6 3. What will happen if you were to try to execute the script as follows? % source welcome good INFO230 - UNIX PRACTICAL EXERCISE 2 For the second week s exercise, make ~/practice/prac2 your current directory 2. 1 Shell variables and lists This section of the work examines the differences in how words are grouped. Create the following script: shellwords!/bin/csh set a1 = One two three set a2 = One two three set a3 = One two three set a4 = (One two three) set a5 = ($a2) set a6 = $a2 $a3 set a7 = ($a2 $a3) echo $a1 $a1 echo $a2 $a2 echo $a3 $a3 echo $a4 $a4 echo $a5 $a5 echo $a6 $a6 echo $a7 $a7 echo $a7[2] 1. What does echo $a1 $a1 do? UP.5

6 2. Test the script and note the difference in the way quoting and grouping affects the contents and number of words considered in the shell variables. 3. Which shell variable has the most number of words? 4. Which shell variables have one word and include spaces in the word? 2. 2 if-then expression Create the following script: checkpattern pattern!/bin/csh if ($argv!= 1) then echo "Usage: checkpattern1 pattern" exit 1 endif if ($argv[1] == abc) then echo "Pattern $argv[1] recognised" else echo "Pattern $argv[1] not recognised" endif Note: spaces must appear before and after the!= and == in the if expression. This script checks if the command line argument pattern matches an internally stored string ( abc in this instance). 1. Test the script using different patterns. 2. Check the argument checking by putting in badly formatted command lines (i.e. 0 or 2 or more command line arguments) 2. 3 prepend script The following script reads input from stdin and places it at the front of a file (prepends it) prepend filename!/bin/csh append stdin to a file usage: prepend filename set tf = /tmp/ppd.$$ set dest = $argv[1] cat - $dest > $tf mv $tf $dest WARNING: Do not forget to put in a CARRIAGE RETURN after the last line of the script. UP.6

7 The directory /tmp is a system directory which all users may access to store temporary files. /tmp is cleaned out regularly (once a week) so do not leave important files there. 1. What is the shell variable $$? 2. Is the file name $tf created unique? Why would we want create a file name this way? 3. Create a temporary file called temp1 and type in a few lines of text (it doesn t matter what it is). Now type: % prepend temp CTRL-D % more temp1 The contents of the file temp1 should now have etc at the front of the file. Examine the line in the script % cat - $dest > $tf How is this command used to do the prepend operation? 4. Pipes can be used to pass the output of one command to the input of another command. prepend takes its input from stdin. Instead of the keyboard we can use a pipe to take the input to prepend from another command e.g. ls. Try this command % ls prepend temp1 Explain how this command works Compressing files and directories You may find it necessary to reduce the amount of disk space you are using since you are running out of disk quota. One way to reduce space is to archive and compress files. 1. In the practice/prac2 directory is a directory called backup. You see that it contains several subdirectories and files. 2. Type %du backup to see how much space it occupies (roughly). 3. Create an archive of backup and its files and subdirectories by typing % tar cfv backup.tar backup UP.7

8 4. Now compress the archive using % compress backup.tar The file backup.tar.z has now been created. 5. Use ls -l to look at how much space it occupies. Compare this with the value from before. 6. Delete the backup directory and its contents (what is a simple and quick way of doing this?) 7. Restore the backup directory by first uncompressing it: % uncompress backup.tar.z 8. Expand the archive by doing: % tar xf backup.tar to restore the backup directory. tar cfv compress backup backup.tar backup.tar.z backup tar xfv backup.tar uncompress 2. 5 Introduction to vi The file practice.vi in ~/practice/prac2 contains a tutorial on using vi. The file contains information on some of the basic commands needed to work with vi and instructions and exercises to help you to learn how to use them. Begin the exercise by entering an editing session with vi as follows: % vi practice.vi and following the instructions in the file. If you get confused and you cannot recover, exit from practice.vi using :q! and start again. If things get really bad, exit using :q! and copy practice.vi.bak and start afresh. UP.8

9 INFO230 - UNIX PRACTICAL EXERCISE 3 For the third week s exercise, make ~/practice/prac3 your current directory. 3.1 Subshells Commands separated by a semi-colon (;) are executed one after the other. Commands enclosed in parenthesis () are executed in a subshell. Execute the following two commands. % ls; date > out1 % (ls; date) > out2 By examining the screen output and the contents of the two files: out1 and out2, explain the difference between the two commands in terms of unix shell execution Conditional execution Copy the fruit file from../prac1 into the current directory. Execute the commands: % grep paper fruit % grep apple fruit Which of these commands did not succeed? The operation is used to execute the second command if the first wasn t successful, and the && is used to execute the second command if the first was successful. Enter the command and examine the output. % grep paper fruit echo Paper not found % grep apple fruit && echo apple found What would happen in the following commands? % grep paper fruit && echo Paper not found % grep apple fruit echo apple found 3. 3 Background execution and job control Execute the following command % du / >& /dev/null & This checks the whole file system and takes a long time, so it should be done in the background. 1. Look up the du command in the man pages. 2. What does >& do? (N.B. that /dev/null is the null device and all output redirected there disappears). UP.9

10 3. The final & means that this command is run as a background process. Examine the list of background jobs using the jobs command after. 4. Now bring that job into the foreground using the fg command. 5. Interrupt execution of the job by typing CTRL-Z. 6. Examine the job list again. 7. Now resume background operation using the bg command. 8. Finally kill the job using the kill command foreach expression Create the following script which lists the size of all non-zero size files (not directories in the current directory). listsize!/bin/csh foreach file (*) if (-f $file &&! -z $file) then set a = `ls -l $file` echo $file $a[5] endif end 1. Test the script by making it executable and running it. To help you create files of zero size for testing this script, there is a program called makezero in the directory which will create a file called zero of size. You can create other zero-size files by copying and renaming the file zero. 2. Carefully examine the script so that you understand what each line is doing. Test your understanding with the following questions: 2.1 What does the following line do? foreach file (*) 2.2 What does the following line do? if (-f $file &&! -z $file) then 2.3 What does the following line do? set a = `ls -l $file` UP.10

11 2.4 What does the following line do? (hint: do an ls -l command on the terminal, why do we echo $a[5]?) echo $file $a[5] 3. 5 Numeric operations Create the following script which counts up to a limit which is specified as a command line argument. count limit!/bin/csh Example usage: count 5 if ($argv!= 1) then echo "Usage: count limit" exit 1 endif if ($argv[1] <= 0) then echo "Limit must be positive" exit 1 endif set i = 1 while (1) echo i = $i + 1 if ($i > $argv[1]) exit end Note: It is important to have a space between and the name of the shell script variable. 1. Test the script by trying different command lines (correctly formatted and not). 2. Carefully examine the script so that you understand what each line is doing. 3. Modify the script so that it has a second argument so that it counts down from limit to when it goes below zero in multiple of the second argument Script execution Scripts can be executed in one of two ways. They can be executed in the current shell using the source command or you can run them in a subshell by changing their file permissions and running them directly like any other command in unix. We will examine the differences here. Create the following script setalias (using the vi editor if you know how). UP.11

12 setalias!/bin/csh set abc = "One two three" echo $abc alias la `ls -a` alias la When the source command is used to execute a script, shell variables and aliases generated by the script do not appear after execution of the script. When direct execution command is used to execute a script, shell variables and aliases will be lost because these variables and alises cannot be passed from a subshell process to a parent process. Make the script executable by doing % chmod u+x setalias 1. Remove any existing shell variables and alises with the same names as used in the shell script. % unset abc % unalias la 2. Now execute the command % source setalias Examine the list of aliases and set variables again. The alias la and abc shell variables should be present. 3. Remove references to abc and la again by doing: % unset abc % unalias la 4. Execute the script as follows: % setalias The shell variable abc and alias la should not be present since they could not be passed back to the parent process. UP.12

13 Unix/C Shell Programming Assign. on Mac INFO230 - UNIX ASSIGNMENT This assignment is due one week after the completion of the third Unix practical session. The unix project assignment is marked out of 100. Make a directory called unix_assign in your home directory and store all your unix assignment files in that directory. Question 1 (xstory name1 name2) (10 marks) Copy the script story2 from the practical exercise 1 to the file xstory and modify it so that Jack and Jill are replaced by two command line arguments ($argv[1] and $argv[2]). The script can then be tested as follows: % xstory Bart Homer Question 2 (loggedin user) (15 marks) Create a script called loggedin which checks to see if a particular user is logged in. It has a single argument and produces one of the two messages, depending on whether the user indicated is logged in at this moment. % loggedin s s is not logged in % loggedin s s is logged in Question 3 (sfind filename c) (15 marks) Create a script called sfind that has two input arguments filename and c. It searches through the file called filename and prints out in increasing alphabetical order all lines beginning with the letter given by the argument c. For example: % sfind fruit p passionfruit peach plum Question 4 (quote) (20 marks) Quoting and the use of escape characters take a bit of practice because of the order in which the C shell processes a command and the different types of quotes. In this assignment question you are to create a script called quote which produces the following messages (use the echo command to produce each line): (n.b. all five (5) lines are to be included below, also, pay particular attention to the exact characters used; especially note lines 3 and 5 regarding quotes and slashes). UA.1

14 Unix/C Shell Programming Assign. on Mac Alice & Wally s Cafe!!^ Welcome ^!! Hot dog s $1.50 Coke\~Pepsi $1.30 *** `All you can eat` *** Question 5 (listexec suffix) (15 marks) Modify the listsize script in the practical exercise 3 to create a script called listexec that (i) (ii) uses the while statement instead of the foreach statement it lists the size of any files with executable permission whose suffix matches a particular pattern. For example: % listexec uu a.uu 256 bett.uu 3456 z1.uu 123 Question 6 (fileman) (25 marks) You are to write a C script, called fileman, that will be used to manage files by allowing them to be copied, moved or deleted with interactive input from the user. It has the following three possible command usage formats: fileman -c filenames fileman -m filenames fileman -r filenames where filenames is a list of one or more file names. The command line options are as follows: -c This is used to copy each file in the list of file names specified in the command line. For each file to be copied the script will prompt the user for the name of the new file. -m This is used to rename (move) each file in the list of file names specified in the command line. For each file the script will prompt the user for the new name of the file. -r This is used to remove each file in the list of file names specified in the command line. The user is prompted for confirmation before a file is removed. Write the script so that it will correctly interpret the command line options and arguments to perform the functions associated with each option. Your script should check for invalid command lines and, if an error occurs, print out a message showing the correct usage formats. UA.2