1. Review The Unix Shells Graham Glass and King Ables,
UNIX for Programmers and Users,
Third Edition, Pearson Prentice Hall, 2003.

2. Reading from Standard Input
Command read
Reads 1 line
Examples
$ read v1 v2
one two
$ echo $v1
one
$ echo $v2
two
$ read v1 v2
one two three four
$ echo $v1
one
$ echo $v2
two three four

3. Arithmetic Bourne shell does not directly do math
Command expr evaluates expressions
Supports
Multiplication (\*), Division (/), Remainder (%)‏
Add (+), Subtract (-)‏
Equal (=), Not Equal (!=)‏
Less (<), Less/Eq (<=), Greater (>), Greater/Eq (>=)‏
And (&), Or (|)‏
Index (locate substring)‏
Match

4. Examples: Integer Operands

5. Environment Variables
$HOME : full pathname of home directory
$PATH : list of directories to search for commands
$MAIL : the full pathname of mailbox
$USER : your username
$SHELL : the full pathname of login shell
$TERM : the type of your terminal

6. Built-In Variables $$ the process ID of the shell
$0 the name of the shell script
$1..$9 $n refers to the nth command line argument
$* a list of all command-line arguments

7. Example

8. Test Command test expression
[ expression ] (equivalent form on some UNIX: if it’s built-in)
Returns a zero if expression evaluates to true
Otherwise, returns a nonzero status.
Examples:
$ test 2 -eq 3;
$ test -e for.sh;
$ test abc = abc;

9. test Command Expression: Files

10. test Command Expression: Strings, Integers, Complex Expressions

11. Case Structure case expression in pattern)‏ list ;; pattern2)‏ list2
...
*) # default
list_n
esac

13. Control Structures: for .. do .. done
for name [in {word}* ] do
list
done
Loops the value of name through each word in the word list, evaluates commands in the list at each iteration.
If no word list is supplied, is used.
break : terminate the loop immediately.
continue : jump to the next iteration.

15. Control Structures: if .. then .. fi
if list1
then
list2
elif list #may be repeated several times
list4
else #may occur zero or one time
list5 fi
Commands in list1 are executed.
If last command succeeds, the list2 is executed.
Otherwise, a successful command list in elif causes the associated then to be executed.

17. Control Structures: until .. do .. done
until list1 do
list2
done
Executes list1
If the last command in list1 succeeds, it ends.
Otherwise, list2 is executed and the process is repeated.
If list2 is empty, the do keyword should be omitted.
break
continue

19. Control Structures: while .. done
while list1 do
list2
done
Executes list1.
If the last command in list1 fails, it ends
Otherwise, list2 is executed and the process is repeated.
If list2 is empty, the do keyword should be omitted.
break
continue