Unix Scripting Lab - Solutions

Part 1: Welcome to Unix

Login to your Unix account
Find your current shell, the default shell and a list of all installed shells.

current shell: echo $0
default shell: echo $SHELL
all shells: cat /etc/shells

List all files and directories in /etc folder ordered by size (hint: man ls).

ls -lS /etc/

Print the current date and time formatted as follows:
Sun 21/03/2010, 14:30 (hint: man date)

date +'%a %d/%m/%Y, %H:%M'

Part 2: Files and directories

Create a new directory for the course in your home folder called lab. Inside, create the following files:
- main.c, game.c, enemy.c, hero.c, a.out
- monster.h, human.h
- .highscore

mkdir lab
cd lab
touch main.c game.c enemy.c hero.c a.out monster.h human.h .highscore

Create the following directories under lab
- Music, Misc, Drivers

mkdir Music Misc Drivers

Place copies of /etc/passwd in all 3 directories (Music, Misc and Drivers)

cp /etc/passwd Music
cp /etc/passwd Misc
cp /etc/passwd Drivers

Create a new text file named myinfo in your home directory and write in it your name, your favorite programming language and why you love unix).

pico myinfo

Create a new directory named myinfo and move the new file you created into it. Did you get an error ? Can you fix it ?

mkdir myinfo.d
mv myinfo myinfo.d
mv myinfo.d myinfo

In the file main.c write a small c program that prints "Hello World" on screen. Compile it with gcc and run the result.

gcc main.c
./a.out

Move all .c files to Music folder

mv main.c game.c enemy.c hero.c Music

Move the folder Music with all its contents to Drivers folder

mv Music Drivers

The program ifconfig displays information about the server's network configuraiton. Find out where it is installed and run it. What is your server's IP address ?

locate ifconfig
/sbin/ifconfig

Try to run rmdir Drivers. Did it work ? Why ?

Didn't work. Directory not empty

Delete the folder Drivers

rm -r Drivers

Part 3: Wildcards

Create a new folder named wildcards, and cd to it.
```
 mkdir wildcards
 cd wildcards
```
Create 5 new folders: src, include, lib, img, Doc
```
 mkdir src include lib img Doc
```
Create 7 new files: src/main.c, src/player.c, include/player.h, lib/zlib.c, img/hero.png, img/player.png, doc/README.txt, doc/test.c.
```
 touch src/main.c src/player.c include/player.h lib/zlib.c img/hero.png img/player.png doc/README.txt doc/test.c
```
Use ls to print the details of the following:
1. All folders whose name starts with a lowercase letter
```
 ls -d [a-z]*
```
2. All folders whose name starts with an uppercase letter
```
 ls -d [A-Z]*
```
3. All folders whose name ends in a vowel (a, e, i, o, or u)
```
 ls -d *[aeiou]
```
4. All folders whose name does not end in a vowel
```
 ls -d *[^aeiou]
```
5. All .c files in src folder
```
 ls src/*.c
```
6. All .c files in all folders
```
 ls */*.c
```
7. All files whose name starts with a p, which are in a folder whose name starts with an i.
```
 ls i*/[ap]*
```
Now delete all .png files from all folders
```
 rm */*.png
```
Using curlies we can create command line repeaters that are not bound to current file status. Try to execute the following: mkdir -p {a,b,c}/{1,2,3}. How many new folders were created ?
Would that still work if you replaced {...} with [...] ? Why ?

Part 4: File Permissions

cd to wildcards folder from previous part.
Change permissions of src/main.c to: r--r--r-- using letter notation.
```
 chmod a=r src/main.c
```
Change permissions of include/player.h to r-xrw--w- using numeric notation.
```
 chmod 562 include/player.h
```
Change permissions of all files under Doc to rw-------, without changing permissions for the Doc folder itself.
```
 chmod 600 Doc/*
```
Change permissions of lib folder and all files inside it to rwxrwxrwx.
```
 chmod -R 777 lib
```
Create a new folder named test and a new file named secret inside test.
```
 mkdir test
 touch test/secret
```
Change permissions of test to ---------. Can you delete just the file secret ? Can you delete test ?
```
 chmod 000 test
```
Read about umask in man csh. Set the mask so all new files are created with permissions: ------r--.
```
 umask 773
```

Part 5: Links

Create a new folder named links and cd to it.
```
 mkdir links; cd links
```
Create 2 files: file1, file2. Inside file1 write names of some programming languages you like, and inside file2 write the names of some programming languages you don't like.
```
 echo perl > file1
 echo python > file2
```
Create file file3 as a symbolic link to file1
```
 ln -s file1 file3
```
Create file file4 as a hard link to file2
```
 ln file2 file4
```
Move file3 to /tmp folder. Can you still read its contents using cat ?
```
 mv file3 /tmp
```
If the answer was no, create a new file3 as a symbolic link to file1, that would survive the move to /tmp.
```
 ln -s `pwd`/file1 file3
 mv file3 /tmp
```
Print out the contents of the first file using cat file3.
```
 cat tmp/file3
```
Delete file1.
```
 rm file1
```
Can you still see its contents through file3 ?
```
 no
```
Now move file4 to your home folder. Can you still see the contents of file2 using only file4 ?
```
mv file4 ~
cat ~/file4
```
Use ls to find the inode number of files: file2, file3, file4.
```
ls -li ~/file4 /tmp/file3 file2
```

Part 6: vim

Try to figure out what the following key sequences do in normal mode: gg, dgg, G, dG, 7G, f<letter>, F<letter>, /<word>.

gg: go to start of file
dgg: delete till start of file
G: go to end of file
dG: delete till end of file
7G: go to line 7
f: go forward in line till letter is found
F: go backward in line till letter is found
/word: search word in file

Copy the file /etc/passwd to your home folder

cp /etc/passwd ~

Start vim on the new copy

vim ~/passwd

Delete the first line

Move the next 4 lines to the end of the file

4ddGp

Save and quit (use ZZ), or quit without saving with ZQ.

Try to figure out what the following key sequences do in insert mode: ^u, ^y, ^t, ^n

^u: delete typed text
^y: copy from line above
^t: insert tab
^n: auto complete

Start vim on existing file

vim ~/passwd

Delete first paragraph

ggd}

Write a new first paragraph telling 5 things you love about vim

imodal editing is cool<Esc>yy5p

Save and Quit (using :wq or ZZ)
Try to figure out what the following key sequences do in vim command line: :!ls, :%!tac, %!sort

!ls - run ls
%!tac - run tac on buffer and send result back to the editor
%!sort - run sort on buffer and send result back to the editor

Create a new key mapping so pressing ^s vim will save the file

inoremap <C-s> <Esc>:w<cr>a

Create a new key mapping so pressing ^x vim will save and exit

inoremap <C-x> <Esc>ZZ

Insert both new key mappings to your .vimrc file

Part 7: Redirections and Pipes

who -u prints out idle time for each connected user. Print out the 3 users who were idle the longest time.
```
  who -u | tr -s ' '  | grep -v old | grep -v \. | sort -t ' ' -k 6 | head -3
```
Print the number of files that have execute permission to their owner.
```
 ls -l | cut -c4 | grep x | wc -l
```
Print the number of files that have execute permissions to their owner, group and others.
```
 ls -l | cut -c4,7,10 | grep xxx | wc -l
```

Print the number of files that were modified on a given date.

 ls -l | tr -s ' ' | cut -d' ' -f5,6 | grep 'Jan 21' | wc -l

Print a list of all files modified TODAY.

 ls -l | tr -s ' ' | cut -d' ' -f5,6 | grep '`date +"%b %d"`' | wc -l

/sbin/ifconfig prints a lot of information about your network connections. Use filters to get only the IP address of the host.
Remember 127.0.0.1 is just a loopback IP, so we should ignore that one.
```
  ifconfig |grep inet|grep -v inet6|grep -v 127.0.0.1
```
Print a list of all Saturday dates on May 2005.
```
 cal 5 2005| cut -c19-20
```
ps -ef prints a list of all processes in the system. Find how many processes match the name csh.
```
 ps -ef | grep csh | grep -v grep
```
The command curl http://graph.facebook.com/103113856395914 prints out information about the facebook page "Unix". Find out how many likes the page has.
```
 curl -s http://graph.facebook.com/103113856395914| rev | cut -d: -f1 | cut -c2-|rev
```

Part 8: Find

Under your home directory, print all files and folders recursively that:
1. Are owned by you
```
 find . -user `whoami`
```
2. Are not owned by you
```
 find . -not -user `whoami`
```
3. Their name ends with a '.c'
```
 find . -name '*.c'
```
4. Their name starts with an a, e, i, o, or u
```
 find . -name '[aeiou]*'
```
5. Weight above 10M
```
 find . -size +10M
```
6. Were created more than 3 hours ago.
```
 find . -cmin +240
```
7. Were modified in the past 2 days.
```
 find . -mtime +2
```
8. Were not accessed in the past week.
```
 find . -ctime +7
```
Create the following files: a.txt, b.txt, c.txt. Now use a single find command to create 3 backup files: a.txt.bak, b.txt.bak and c.txt.bak (as copies of the original files).
```
 find . -type f -exec cp '{}' '{}'.bak \;
```

Part 9: Regular Expressions

Given the following lists of positive and negative words, type a regular expression that matches all words in positive, but doesn't math any of the words in negative.

Positive Negative

pit pt

spot Pot

spate peat

slap two part

respite

Regexp: p.t

Positive Negative

rap them aleht

tapeth happy them

apth tarpth

wrap/try Apt

sap tray peth

87ap9th tarreth

apothecary ddapdg

apples

shape the

Regexp: p.?t
Write a regular expression to accept any binary string (only 0s and 1s)
```
 ^[01]+$
```
A binary string represents an even number if it ends with a 0. Write a regular expression to match an even number represented as a binary string.
```
 ^[01]*0$
```
Write a regular expression to accept any hexa-decimal string
```
 ^[0-9a-fA-F]+$
```
Print all lines from ls -l which represent a folder
```
 ls -l | egrep '^d'
```
Print all files and folders whose name starts with an uppercase letter and ends with a number.
```
 ls | egrep '^[A-Z].*[0-9]$'
```
Print all files (no folders) which have execute permission to owner
```
 ls -l | egrep '^-..x'
```
All lines from ls -l which start with a -, an l or a d
```
 ls -l | egrep '^[-ld]'
```
All lines from ls -l that are longer than 50 characters
```
ls -l | egrep '.{50}'
```
All lines from ls -l that have an even length (בעלות אורך זוגי)
```
ls -l | egrep '^(..)*$'
```

Positive	Negative
pit	pt
spot	Pot
spate	peat
slap two	part
respite

Positive	Negative
rap them	aleht
tapeth	happy them
apth	tarpth
wrap/try	Apt
sap tray	peth
87ap9th	tarreth
apothecary	ddapdg
	apples
	shape the

Part 10: Aliases and Startup Files

Write the following aliases:

ll => ls -l
c => clear
rm => rm -i

cp => cp -i

 alias ll "ls -l"
 alias c clear
 alias rm "rm -i"
 alias cp "cp -i"

Now try to overwrite an existing file with cp. Did you get a prompt?
```
 yes
```
Next, use the unaliased version of cp to overwrite a file without the prompt (But don't unalias it).
```
 \cp /etc/passwd ~/copy
```
Write the following aliases:
1. count_files => print the number of files in current directory
2. bysize => list all files ordered by sizes (from large to small)
3. lmod => list all files modified in date (date is a date string from ls -l)
4. ff => find a file by a partial name. For example, ff ba should print all files and folders whose name contains ba.
```
 alias count_files "find . -type f -maxdepth 1 | wc -l"
 alias bysize "ls -lS | egrep -v '^d'"
 alias lmod "ls -l | egrep "
 alias ff "find . -name '*'\!*'*'"
```

Part 13: Processes and Jobs

Run the program xeyes in a terminal.
```
 xeyes
```
From the same terminal, freeze xeyes with ^Z.
List all jobs in the terminal. Can you find xeyes ?
```
 jobs
```
Send xeyes to resume in the background
```
 bg
```
Terminal xeyes using kill
```
 kill %1
```
The command ps -u <user> prints out all processes running on the server owned by user. Terminal all processes named vim running under your user, in a single command.
```
 ps -ef | grep vim | awk '{print $2}' | xargs kill -9
```

Part 14 - awk

Add a blank line after each line of input

ls -l | awk '{ printf("%s\n\n", $0) }'

Print a '> ' in the beginning of each line

ls -l | awk '{ printf("> %s\n", $0) }'

Use awk that take a file name as input and performs:
1. If a line starts with #, replace each character with a -
2. For all other lines, replace each character with a . (print result to screen)

cat /etc/shells | awk '/^[^#]/ { gsub(".", "-", $0) } /^#/ { gsub(".", ".", $0) } { print }'

Replace the first and last word in every line
The command /sbin/ifconfig prints out information about network interfaces. Here's a sample output for the command:


en3: flags=8963 mtu 1500
        options=60
        ether 32:00:18:24:c0:00
        media: autoselect 
        status: inactive
p2p0: flags=8843 mtu 2304
        ether 06:38:35:47:96:24
        media: autoselect
        status: inactive

Use awk to parse the information generated by ifconfig and create an information file for each network interface. For example the above interface should produce two files: first is named en3.info and has the en3 block, and the second is named p2p0.info and has the second block

/sbin/ifconfig | awk '/^[a-z]/ { fname = $1 } { print > fname }'

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