Increment variable value by 1 ( shell programming)

You can use an arithmetic expansion like so:

i=$((i+1))

or declare i as an integer variable and use the += operator for incrementing its value.

declare -i i=0
i+=1

or use the (( construct.

((i++))

The way to use expr:

i=0
i=`expr $i + 1`

the way to use i++

((i++)); echo $i;

Tested in gnu bash