10.4. Testing and Branching

#!/bin/bash

echo; echo "Hit a key, then hit return."
read Keypress

case "$Keypress" in
  [a-z]   ) echo "Lowercase letter";;
  [A-Z]   ) echo "Uppercase letter";;
  [0-9]   ) echo "Digit";;
  *       ) echo "Punctuation, whitespace, or other";;
esac  # Allows ranges of characters in [square brackets].

# Exercise:
# --------
# As the script stands, # it accepts a single keystroke, then terminates.
# Change the script so it accepts continuous input,
# reports on each keystroke, and terminates only when "X" is hit.
# Hint: enclose everything in a "while" loop.

exit 0

#!/bin/bash

# Crude address database

clear # Clear the screen.

echo "          Contact List"
echo "          ------- ----"
echo "Choose one of the following persons:" 
echo
echo "[E]vans, Roland"
echo "[J]ones, Mildred"
echo "[S]mith, Julie"
echo "[Z]ane, Morris"
echo

read person

case "$person" in
# Note variable is quoted.

  "E" | "e" )
  # Accept upper or lowercase input.
  echo
  echo "Roland Evans"
  echo "4321 Floppy Dr."
  echo "Hardscrabble, CO 80753"
  echo "(303) 734-9874"
  echo "(303) 734-9892 fax"
  echo "revans@zzy.net"
  echo "Business partner & old friend"
  ;;
# Note double semicolon to terminate each option.

  "J" | "j" )
  echo
  echo "Mildred Jones"
  echo "249 E. 7th St., Apt. 19"
  echo "New York, NY 10009"
  echo "(212) 533-2814"
  echo "(212) 533-9972 fax"
  echo "milliej@loisaida.com"
  echo "Girlfriend"
  echo "Birthday: Feb. 11"
  ;;

# Add info for Smith & Zane later.

          * )
   # Default option.	  
   # Empty input (hitting RETURN) fits here, too.
   echo
   echo "Not yet in database."
  ;;

esac

echo

#  Exercise:
#  --------
#  Change the script so it accepts continuous input,
#+ instead of terminating after displaying just one address.

exit 0

#!/bin/bash
# Using command substitution to generate a "case" variable.

case $( arch ) in   # "arch" returns machine architecture.
i386 ) echo "80386-based machine";;
i486 ) echo "80486-based machine";;
i586 ) echo "Pentium-based machine";;
i686 ) echo "Pentium2+-based machine";;
*    ) echo "Other type of machine";;
esac

exit 0

#!/bin/bash
# match-string.sh: simple string matching

match_string ()
{
  MATCH=0
  NOMATCH=90
  PARAMS=2     # Function requires 2 arguments.
  BAD_PARAMS=91

  [ $# -eq $PARAMS ] || return $BAD_PARAMS

  case "$1" in
  "$2") return $MATCH;;
  *   ) return $NOMATCH;;
  esac

}  


a=one
b=two
c=three
d=two


match_string $a     # wrong number of parameters
echo $?             # 91

match_string $a $b  # no match
echo $?             # 90

match_string $b $d  # match
echo $?             # 0


exit 0		    

#!/bin/bash
# isalpha.sh: Using a "case" structure to filter a string.

SUCCESS=0
FAILURE=-1

isalpha ()  # Tests whether *first character* of input string is alphabetic.
{
if [ -z "$1" ]                # No argument passed?
then
  return $FAILURE
fi

case "$1" in
[a-zA-Z]*) return $SUCCESS;;  # Begins with a letter?
*        ) return $FAILURE;;
esac
}             # Compare this with "isalpha ()" function in C.


isalpha2 ()   # Tests whether *entire string* is alphabetic.
{
  [ $# -eq 1 ] || return $FAILURE

  case $1 in
  *[!a-zA-Z]*|"") return $FAILURE;;
               *) return $SUCCESS;;
  esac
}

isdigit ()    # Tests whether *entire string* is numerical.
{             # In other words, tests for integer variable.
  [ $# -eq 1 ] || return $FAILURE

  case $1 in
  *[!0-9]*|"") return $FAILURE;;
            *) return $SUCCESS;;
  esac
}



check_var ()  # Front-end to isalpha ().
{
if isalpha "$@"
then
  echo "\"$*\" begins with an alpha character."
  if isalpha2 "$@"
  then        # No point in testing if first char is non-alpha.
    echo "\"$*\" contains only alpha characters."
  else
    echo "\"$*\" contains at least one non-alpha character."
  fi  
else
  echo "\"$*\" begins with a non-alpha character."
              # Also "non-alpha" if no argument passed.
fi

echo

}

digit_check ()  # Front-end to isdigit ().
{
if isdigit "$@"
then
  echo "\"$*\" contains only digits [0 - 9]."
else
  echo "\"$*\" has at least one non-digit character."
fi

echo

}

a=23skidoo
b=H3llo
c=-What?
d=What?
e=`echo $b`   # Command substitution.
f=AbcDef
g=27234
h=27a34
i=27.34

check_var $a
check_var $b
check_var $c
check_var $d
check_var $e
check_var $f
check_var     # No argument passed, so what happens?
#
digit_check $g
digit_check $h
digit_check $i


exit 0        # Script improved by S.C.

# Exercise:
# --------
#  Write an 'isfloat ()' function that tests for floating point numbers.
#  Hint: The function duplicates 'isdigit ()',
#+ but adds a test for a mandatory decimal point.

#!/bin/bash

PS3='Choose your favorite vegetable: ' # Sets the prompt string.

echo

select vegetable in "beans" "carrots" "potatoes" "onions" "rutabagas"
do
  echo
  echo "Your favorite veggie is $vegetable."
  echo "Yuck!"
  echo
  break  # if no 'break' here, keeps looping forever.
done

exit 0

#!/bin/bash

PS3='Choose your favorite vegetable: '

echo

choice_of()
{
select vegetable
# [in list] omitted, so 'select' uses arguments passed to function.
do
  echo
  echo "Your favorite veggie is $vegetable."
  echo "Yuck!"
  echo
  break
done
}

choice_of beans rice carrots radishes tomatoes spinach
#         $1    $2   $3      $4       $5       $6
#         passed to choice_of() function

exit 0