Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
}
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`
f=AbcDef
g=27234
h=27a34
i=27.34
# Command substitution.
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.
select
# 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.
The select construct, adopted from the Korn Shell, is yet another tool for building menus.
select variable [in list]
do
command...
break
done
This prompts the user to enter one of the choices presented in the variable list. Note that select uses
the PS3 prompt (#? ) by default, but that this may be changed.
Example 10−29. Creating menus using select
Chapter 10. Loops and Branches 122