1. Part 1: Basic Commands/Utilities

2. Final Exam May 17th 3:00~4:00pm S-3-143
Same types of questions as in mid-term

3. Basic Utilities ls, cat, echo ls -l ls -a cat file1 file2 file3 …
e.g., regular file or directory, permissions, file size
ls -a
cat file1 file2 file3 …
echo “hello world” > file
echo $VAR, echo hello*
echo –n “hello world”

4. Basic Utilities more, less, head, tail pwd, cd
head -5 file
tail -f file
pwd, cd
cp, mv, rm, mkdir, rmdir
‘-i’ option
‘-r’ option:
rm –r dir1, cp –r dir1 dir2
rmdir an empty directory

5. Basic Utilities sort, wc, grep, |(pipe) wc -l file, wc –c file
grep “keyword” file
grep -v
sort linux | head -5
command1 | command2
command1 > temp
command2 < temp
rm temp

6. Part 2: File Systems

7. Filename and Path Hierarchical tree structure Absolute path name
ls /home/it244/it244
Relative path name
cd /home/it244
ls it244
‘.’ ‘..’ ‘~’
‘*’ ‘?’
echo hello*, echo ./.?a*

8. Access Permissions r, w, x (chmod) Execute permission of a directory
chmod a+rw file
chmod a=rx file
chmod 644 file
Execute permission of a directory
A directory is a table of files (filename:meta)
Executable means searchable

9. Access Permissions Operations on book/book1 ls book/book1
book ( x )
cat book/book1
book1 ( r ), book ( x )
rm book/book1
book ( xw ), book1 ( w )

10. Links Hard link and soft link Hard link cannot refer to a directory
Soft link can point to a nonexistent file
$ ln -s hello hello.sl
$ rm hello
$ echo “new” > hello
$ cat hello.sl
new

11. Part 3: Bash/Shell Scripting

12. Execute Commands Foreground and background jobs Group commands
command &, CTRL+Z
difference between a suspended job and a background job, PID
jobs, ps, kill, bg, fg
Group commands
(cmd1; cmd2; cmd3)

13. Redirection Standard input, output, error output
cat file1 file2 > out 2>err
cat file1 file2 &> out
cat file1 file2 > out 2>&1
Redirected output will not be displayed on the screen.

14. Variables System variables User defined variables $PATH, $PWD, $HOME
VAR=hello
export VAR=hello
declare; declare -x

15. Variables New shell for executing a script $cat script1 echo $VAR
VAR=new
$VAR=old;./script1;echo $VAR
$VAR=new ./script1;echo $VAR
$export VAR=old;./script1;echo $VAR

16. Expansion/ Quote Types Single quote suspends all expansions
echo hello*; echo ~
echo $VAR
echo $(pwd)
echo $((1+1))
VAR=hello*
Single quote suspends all expansions

17. Control Flow if..then..fi, if..then..else..fi, while test-command do
commands
done
for loop-index in argument-list

18. Control Flow Conditions test $# -eq 0 [ -f “$1” ]
[ condition1 –a condition2 ], -o
[[ && ]], (( || ))
Exit status $?
if [ read <file $line ] …

19. Expressions Arithmetic Logic a=5;b=3;echo $((a%b)) echo $((a+++3))
cat abc && ls
echo $?

20. Control Flow Boolean operators cond1 cond2 cond1 && cond2
True
False
false

21. Control Flow Boolean operators Short circuiting $((a=2, b=2))
$echo $a $b
$((--a>2 || b++))

22. Control Flow Boolean operators Short circuiting
(($#==2)) || echo "Usage:require two arguments”
mkdir $1 && cp file1 $1

23. Variables Arguments $$, $? $1-$n, $0, $#, $@ set shift set a 123 hello
echo $1 $2 $3
set $(date)
shift
echo
$$, $?

24. File I/O exec read exec 3 < infile Write to a file
exec 4 > outfile
read
read -p “Enter sth: ” input1 input2
read <&3 line, read –u3 line
Determine the end of a file
$line has no value
‘read’ returns false
Write to a file
echo “abc” >&4

25. Expressions Arithmetic Logic a=5;b=3;echo $((a%b)) echo $((a+++3))
cat abc && ls
echo $?

26. Part 4: Perl/AWK/SED

27. Run a Program Perl AWK SED perl simple.pl perl –e ‘print “hi\n”’
gawk -f simple file
gawk ‘/chevy/ {print}’ file
SED
sed -f simple file
sed ‘/line/ p’ file
Stand-alone scripts
#!/usr/bin/perl
#!/usr/bin/gawk -f
#!/bin/sed -f

28. Patterns AWK SED awk ‘/chevy/ {print}’ cars gawk ‘$1 ~ /h/’ cars
gawk ‘$5 > 2000 && $5<6000’ cars
SED
sed -n ‘3,6 p’ lines
sed –n ‘s/line/sentence/w temp’ lines

29. File I/O in perl Read Write open ($infile, '<', “filename”);
while ($line=<$infile>){
print $line; }
$line=<>
Write
$filename="./log";
open($outfile,'>',$filename);
print $outfile "Hello world!\n";

30. Questions
If we execute the following sequence of commands in order, what are the values of variables a, b and the output AFTER executing each line?
$((a=1, b=2))
$echo $((a b++)) a=_0_, b=_3_, output=_3_
$echo $((a b)) a=_1_, b=_4_, output=_4_

31. Questions Read the following shell script and explain its function.
$ cat script1
#!/bin/bash
count=0
for i in *
then
((count++)) fi
echo $count

32. Questions Read the following shell script and answer the questions
$cat script1
#!/bin/bash
exec 3<$1
exec 4<$2
exec 5>$3
while read line <&3 do
echo “$line” >&5
done
while read line <&4
Q1. The script requires 3 filenames as arguments, e.g.,
./script1 file1 file2 file3
Which files are input files and which are output files?
Q2. Inside the while-loop, why variable “$line” has to
be enclosed by double quotes?