3.30. Bash, version 2

   1 #!/bin/bash
   2 
   3 # String expansion.
   4 # Introduced in version 2 of bash.
   5 
   6 # Strings of the form $'xxx'
   7 # have the standard escaped characters interpreted. 
   8 
   9 echo $'Ringing bell 3 times \a \a \a'
  10 echo $'Three form feeds \f \f \f'
  11 echo $'10 newlines \n\n\n\n\n\n\n\n\n\n'
  12 
  13 exit 0

   1 #!/bin/bash
   2 
   3 # Indirect variable referencing.
   4 # This has a few of the attributes of references in C++.
   5 
   6 
   7 a=letter_of_alphabet
   8 letter_of_alphabet=z
   9 
  10 # Direct reference.
  11 echo "a = $a"
  12 
  13 # Indirect reference.
  14 echo "Now a = ${!a}"
  15 # The ${!variable} notation is greatly superior to the old "eval var1=\$$var2"
  16 
  17 echo
  18 
  19 t=table_cell_3
  20 table_cell_3=24
  21 echo "t = ${!t}"
  22 table_cell_3=387
  23 echo "Value of t changed to ${!t}"
  24 # Useful for referencing members
  25 # of an array or table,
  26 # or for simulating a multi-dimensional array.
  27 # An indexing option would have been nice (sigh).
  28 
  29 
  30 exit 0

   1 #!/bin/bash2
   2 # Must specify version 2 of bash, else might not work.
   3 
   4 # Cards:
   5 # deals four random hands from a deck of cards.
   6 
   7 UNPICKED=0
   8 PICKED=1
   9 
  10 DUPE_CARD=99
  11 
  12 LOWER_LIMIT=0
  13 UPPER_LIMIT=51
  14 CARDS_IN_SUITE=13
  15 CARDS=52
  16 
  17 declare -a Deck
  18 declare -a Suites
  19 declare -a Cards
  20 # It would have been easier and more intuitive
  21 # with a single, 3-dimensional array. Maybe 
  22 # a future version of bash will support
  23 # multidimensional arrays.
  24 
  25 
  26 initialize_Deck ()
  27 {
  28 i=$LOWER_LIMIT
  29 until [ $i -gt $UPPER_LIMIT ]
  30 do
  31   Deck[i]=$UNPICKED
  32   let "i += 1"
  33 done
  34 # Set each card of "Deck" as unpicked.
  35 echo
  36 }
  37 
  38 initialize_Suites ()
  39 {
  40 Suites[0]=C #Clubs
  41 Suites[1]=D #Diamonds
  42 Suites[2]=H #Hearts
  43 Suites[3]=S #Spades
  44 }
  45 
  46 initialize_Cards ()
  47 {
  48 Cards=(2 3 4 5 6 7 8 9 10 J Q K A)
  49 # Alternate method of initializing array.
  50 }
  51 
  52 pick_a_card ()
  53 {
  54 card_number=$RANDOM
  55 let "card_number %= $CARDS"
  56 if [ ${Deck[card_number]} -eq $UNPICKED ]
  57 then
  58   Deck[card_number]=$PICKED
  59   return $card_number
  60 else  
  61   return $DUPE_CARD
  62 fi
  63 }
  64 
  65 parse_card ()
  66 {
  67 number=$1
  68 let "suite_number = number / CARDS_IN_SUITE"
  69 suite=${Suites[suite_number]}
  70 echo -n "$suite-"
  71 let "card_no = number % CARDS_IN_SUITE"
  72 Card=${Cards[card_no]}
  73 printf %-4s $Card
  74 # Print cards in neat columns.
  75 }
  76 
  77 seed_random ()
  78 {
  79 # Seed random number generator.
  80 seed=`eval date +%s`
  81 let "seed %= 32766"
  82 RANDOM=$seed
  83 }
  84 
  85 deal_cards ()
  86 {
  87 echo
  88 
  89 cards_picked=0
  90 while [ $cards_picked -le $UPPER_LIMIT ]
  91 do
  92   pick_a_card
  93   t=$?
  94 
  95   if [ $t -ne $DUPE_CARD ]
  96   then
  97     parse_card $t
  98 
  99     u=$cards_picked+1
 100     # Change back to 1-based indexing (temporarily).
 101     let "u %= $CARDS_IN_SUITE"
 102     if [ $u -eq 0 ]
 103     then
 104      echo
 105      echo
 106     fi
 107     # Separate hands.
 108 
 109     let "cards_picked += 1"
 110   fi  
 111 done  
 112 
 113 echo
 114 
 115 return 0
 116 }
 117 
 118 
 119 # Structured programming:
 120 # entire program logic modularized in functions.
 121 
 122 #================
 123 seed_random
 124 initialize_Deck
 125 initialize_Suites
 126 initialize_Cards
 127 deal_cards
 128 
 129 exit 0
 130 #================
 131 
 132 
 133 
 134 # Exercise 1:
 135 # Add comments to thoroughly document this script.
 136 
 137 # Exercise 2:
 138 # Revise the script to print out each hand sorted in suites.
 139 # You may add other bells and whistles if you like.
 140 
 141 # Exercise 3:
 142 # Simplify and streamline the logic of the script.