Find out yourself

2. Find out yourself • sh passwordNOTCORRECT.sh • please enter password, • you have 3 attempts • this is attempt number 1 • xyz • password NOT correct • this is attempt number 2 • pass • password correct

3. [: =: unary operator expected • sh passwordNOTCORRECT.sh • please enter password, • you have 3 attempts • this is attempt number 1 • passwordNOTCORRECT.sh: line 17: [: =: unary operator expected • password NOT correct • this is attempt number 2

4. Body of password code • echo this is attempt number $i • read PASSWORD • if • [ $PASSWORD = $data ] • then • echo password correct && ((i = 4)) • else • echo password NOT correct • fi

5. arrays • myVal=5 • echo myVal = $myVal • i=3 • array1[$i]=$myVal • echo array1[i] = ${array1[$i]}

6. Initializing arrays in order • array2=(x y z) • echo array2[0] = ${array2[0]} • echo array2[1] = ${array2[1]} • echo array2[2] = ${array2[2]}

7. Initializing arrays out of order • array3=([0]=a [34]=b [12]=c) • echo array3[0] = ${array3[0]} • echo array3[12] = ${array3[12]} • echo array3[34] = ${array3[34]} • echo array3[3] = ${array3[3]}

8. Elements and length of array • arrayElements=${array3[@]} • arrayLength=${#array3[@]} • echo arrayElements=\${array3[@]} $arrayElements • echo arrayLength=\${#array3[@]} $arrayLength

9. Ranges in an array • #return all from position 2 to end. • echo {array3[@]:2} ${array3[@]:2} • #returns all from position 1 and 2 • echo {array3[@]:1:2} ${array3[@]:1:2}

10. Values in a array • #tells what index have values • echo \${!array3[@]} ${!array3[@]} • ${!array3[@]}

11. Removing an item in array • #unsets an item in the array • unset array3[1] • echo arrayLength=\${#array3[@]} $arrayLength • echo arrayElements=\${array3[@]} $arrayElements

12. Clearing an array • #unsets all items in array (ie clears the array) • unset array3[@] • echo arrayLength=\${#array3[@]} $arrayLength • echo arrayElements=\${array3[@]} $arrayElements

13. function • function number { • echo $1 • } • echo "function is " • number "a" "b" "c"

14. scope() • { • local x=1 • y=2 • echo "x=$x" • echo "y=$y" • } • scope • echo "x=$x" • echo "y=$y"

15. recursive.sh • echo this is a shell • sh recursive.sh

16. until • read ANS • until [ $ANS = 'bye' ] • do • echo you typed $ANS • echo type something • read ANS • done

17. Exit value • echo now type \'echo \$\?\' and see what happens • exit 4

18. ${variable} • # it is better to rename this file. • MYSTRING="start" • echo MYSTRING is my $MYSTRING • MYSTRING=${MYSTRING}end • echo MYSTRING is my $MYSTRING

19. Variable length • VARIABLE=THIS • echo ${#VARIABLE} • VARIABLE="this is a very long variable" • echo ${#VARIABLE}

20. Case statement • echo -n "Enter a number between 1 and 3 inclusive > " • read character • case $character in • 1 ) echo "You entered one." • ;; • 2 ) echo "You entered two." • ;; • 3 ) echo "You entered three." • ;; • * ) echo "You did not enter a number" • echo "between 1 and 3." • esac

21. Case statement – letter or digit • echo -n "Type a digit or a letter > " • read character • case $character in • # Check for letters • [a-z] | [A-Z] ) echo "You typed the letter $character" • ;; • # Check for digits • [0-9] ) echo "You typed the digit $character" • ;; • # Check for anything else • * ) echo "You did not type a letter or a digit" • esac

22. Positional parameter 1 • if [ "$1" != "" ]; then • echo "Positional parameter 1 contains something" • else • echo "Positional parameter 1 is empty" • fi

23. Positional parameter 2 • if [ $# -gt 0 ]; then • echo "Your command line contains $# arguments" • else • echo "Your command line contains no arguments" • fi

24. Positional parameter 3 • for i in $@; do • echo $i • done • for i in "$@"; do • echo $i • done • for i in $*; do • echo $i • done • for i in "$*"; do • echo $i • done

25. What line number • echo this is line number $LINENO • echo and this is $LINENO • Why is the useful? • What does the user care about this?