The main difference between sh -x and sh -v:
o sh -v shows each statement before it is executed
o sh -x shows the actual variable values after substitution
o often sh -x gives more useful debugging information

$ sh ./jot 2 5
2 3 4 5 

$ sh -v ./jot 2 5
#! /bin/sh

prog=$(basename $0)
basename $0
[ $# -ne 2 ] && echo usage: $prog start finish && exit
start=$1
end=$2
i=$start
while [ $i -le $end ]
do
    echo -n "$i "
    i=$(expr $i + 1)
done
2 expr $i + 1
3 expr $i + 1
4 expr $i + 1
5 expr $i + 1
echo

$ sh -x ./jot 2 5
++ basename ./jot
+ prog=jot
+ '[' 2 -ne 2 ']'
+ start=2
+ end=5
+ i=2
+ '[' 2 -le 5 ']'
+ echo -n '2 '
2 ++ expr 2 + 1
+ i=3
+ '[' 3 -le 5 ']'
+ echo -n '3 '
3 ++ expr 3 + 1
+ i=4
+ '[' 4 -le 5 ']'
+ echo -n '4 '
4 ++ expr 4 + 1
+ i=5
+ '[' 5 -le 5 ']'
+ echo -n '5 '
5 ++ expr 5 + 1
+ i=6
+ '[' 6 -le 5 ']'
+ echo