Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
Most persons avoid dc, since it requires non−intuitive RPN input. Yet it has its uses.
Example 12−36. Converting a decimal number to hexadecimal
#!/bin/bash
# hexconvert.sh: Convert a decimal number to hexadecimal.
BASE=16
# Hexadecimal.
if [ −z "$1" ]
then
echo "Usage: $0 number"
exit $E_NOARGS
# Need a command line argument.
fi
# Exercise: add argument validity checking.
hexcvt ()
{
if [ −z "$1" ]
then
echo 0
return # "Return" 0 if no arg passed to function.
fi
echo ""$1" "$BASE" o p" | dc
# "o" sets radix (numerical base) of output.
# "p" prints the top of stack.
# See 'man dc' for other options.
return
}
hexcvt "$1"
exit 0
Studying the info page for dc gives some insight into its intricacies. However, there seems to be a
small, select group of dc wizards who delight in showing off their mastery of this powerful, but
arcane utility.
Example 12−37. Factoring
#!/bin/bash
# factr.sh: Factor a number
MIN=2 # Will not work for number smaller than this.
E_NOARGS=65
E_TOOSMALL=66
if [ −z $1 ]
then
echo "Usage: $0 number"
exit $E_NOARGS
fi
if [ "$1" −lt "$MIN" ]
Chapter 12. External Filters, Programs and Commands 203