函数increment

#!/bin/sh
# Scriptname: do_increment
increment ()  {
 sum=`expr $1 + 1`
 return $sum   # Return the value of sum to the script.
}
echo  -n "The sum is "
increment 5    # Call function increment; pass 5 as a
               # parameter. 5 becomes $1 for the increment
               # function.
echo $?        # The return value is stored in $?
echo  $sum     # The variable "sum" is known to the function,
               # and is also known to the main script.