Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
alt_return_test 256
echo "return value = $Return_Val" # 256
alt_return_test 257
echo "return value = $Return_Val" # 257
alt_return_test 25701
echo "return value = $Return_Val" #25701
Example 23−6. Comparing two large integers
#!/bin/bash
# max2.sh: Maximum of two LARGE integers.
# This is the previous "max.sh" example,
# modified to permit comparing large integers.
EQUAL=0
# Return value if both params equal.
MAXRETVAL=256 # Maximum positive return value from a function.
E_PARAM_ERR=−99999 # Parameter error.
E_NPARAM_ERR=99999 # "Normalized" parameter error.
max2 ()
# Returns larger of two numbers.
{
if [ −z "$2" ]
then
return $E_PARAM_ERR
fi
if [ "$1" −eq "$2" ]
then
return $EQUAL
else
if [ "$1" −gt "$2" ]
then
retval=$1
else
retval=$2
fi
fi
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− #
# This is a workaround to enable returning a large integer
# from this function.
if [ "$retval" −gt "$MAXRETVAL" ] # If out of range,
then
# then
let "retval = (( 0 − $retval ))" # adjust to a negative value.
# (( 0 − $VALUE )) changes the sign of VALUE.
fi
# Large *negative* return values permitted, fortunately.
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− #
return $retval
}
max2 33001 33997
return_val=$?
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− #
if [ "$return_val" −lt 0 ]
# If "adjusted" negative number,
Chapter 23. Functions 281